Home » Public Forums » GMCnet » Towing Gearing (gearset while towing)
| Towing Gearing [message #354549] |
Fri, 08 May 2020 19:25  |
 |
Husker92592
Messages: 137
Registered: August 2013
Location: Temecula ca
Karma: -4
|
Senior Member |
|
|
Has anyone out there towed anything with a 3.42 or a 3.55 gear set in their coach? Has anyone done any calculations of the towed vehicle based on the changes from the stock gearset to the 3.42 or 3.55?
thanks
1974 GMC Sequoia 26'
|
|
|
|
|
|
| Re: [GMCnet] Towing Gearing [message #354553 is a reply to message #354550] |
Fri, 08 May 2020 21:33  |
powwerjon
Messages: 849
Registered: March 2013
Karma: -2
|
Senior Member |
|
|
Here is the calculation for different tire sized and gear ratios, Don Brown this a number of years ago.
http://www.gmceast.com/technical/Brown_Drive_Tire_Ratios.pdf
J.R. Wright
GMC Great Laker MHC
GMCGL Tech Editor
GMC Eastern States Charter Member
GMCMI
78 GMC Buskirk 29.5’ Stretch
75 GMC Avion (Under Reconstruction)
Michigan
Home again after another adventure.
> On May 8, 2020, at 8:46 PM, James Hupy via Gmclist wrote:
>
> I only towed a box trailer 7000 miles or so with a 78 26 ft. ROYALE.
> Crossed the rockies twice, the Grapevine, the Tehachapi grade, and the
> Siskiyou's north on I-5 with 3:70 final drive and a 403. Wouldn't trade it
> for anything else.
> Jim Hupy
> Salem, Oregon
>
> On Fri, May 8, 2020, 5:25 PM Grant Schaffer via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> Has anyone out there towed anything with a 3.42 or a 3.55 gear set in
>> their coach? Has anyone done any calculations of the towed vehicle based on
>> the
>> changes from the stock gearset to the 3.42 or 3.55?
>> thanks
>> --
>> 1974 GMC Sequoia 26'
>>
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
|
|
|
|
| Re: Towing Gearing [message #354612 is a reply to message #354549] |
Mon, 11 May 2020 16:14 |
tgeiger
Messages: 518
Registered: February 2006
Location: kansas city
Karma: -1
|
Senior Member |
|
|
I looked at the table Jim and not exactly sure how your numbers for say the 3:42 ratio would change much per the 225 R75 16 tire size. These are my specs but not sure how this answers the question on the transmission ratios posted. My engine is a 455. I’m also interested in towing and would like to know my towing weight limits?
Thanks
TG
Tom Geiger
76 Eleganza II
KCMO
|
|
|
|
| Re: [GMCnet] Towing Gearing [message #354616 is a reply to message #354612] |
Mon, 11 May 2020 16:30 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
|
|
I have known of one instance that a GMC Motorhome 26 foot, with adequate
hitch hookups towed a trailer full of race bikes, tools, gear, beer, etc.
That had an all up weight of over 16,000 pounds. 455 engine, 3:70 limited
slip differential. Ran back and forth across the Cascades at Snowqualimy
Pass, and Santiam Pass with no problems. Easily would exceed 70 mph so
equipped.
Another with the same gearing tows race cars in a tandem axle trailer
with an all up weight of over 20,000 pounds with a 403. No issues there
either. I would consider those examples to be about the high limit of tow
weights.
Jim Hupy
Salem, Oregon
On Mon, May 11, 2020, 2:15 PM tom geiger via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I looked at the table Jim and not exactly sure how your numbers for say
> the 3:42 ratio would change much per the 225 R75 16 tire size. These are my
> specs but not sure how this answers the question on the transmission
> ratios posted. My engine is a 455. I’m also interested in towing and would
> like to know my towing weight limits?
>
> Thanks
> TG
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
|
|
|
|
| Re: Towing Gearing [message #354623 is a reply to message #354549] |
Mon, 11 May 2020 19:48 |
tgeiger
Messages: 518
Registered: February 2006
Location: kansas city
Karma: -1
|
Senior Member |
|
|
Wow, that would for be more than a toad I was considering. Did not know she was capable of towing that much.
TG
Tom Geiger
76 Eleganza II
KCMO
|
|
|
|
|
|
| Re: Towing Gearing [message #354626 is a reply to message #354549] |
Mon, 11 May 2020 20:28 |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
|
Senior Member |
|
|
Lower gearing will better the towing experience.
If you search opinions you will see if you have a 403, most (almost all) will say 3.7 gearing is best.
In 455
Engine coaches the opinions vary significantly. You want to tow heavy, go with lower gears such as 3.7.
My opinion on coaches I have driven, that 3.7 is a little low for most purposes, but I probably would reccomend them if you plan to do lots of mountain passes. In midwest
Most traffic is 70mph+. So 3.7 at speeds over 70 Makes a loud engine. Makes me nervous.
I have never been disappointed in any gear change for drivability off the line. I have 3.21 and
That little change made all the difference in starting off a stop light.
My friend has 3.42 we put in his and same thing. Mine cruises perfect empty, but his drives better hauling his tracker.
As far as towing is concerned,
I have hauled 4000-5000 pounds. Normally my towd is about 3300-3500. And I have hauled other lighter items.
It seems I would prefer to be light as practical with towing things 2000 pounds I really dont notice a big drag. But closer to 3000 you accelerate a bit slower and have to give it
More gas to hold speed going up slight inclines.
It also depends on how you want to drive. Hauling 4000 pounds at 55-60mph compared
To 65-70
Is an entirely different thing.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
[Updated on: Mon, 11 May 2020 20:31] Report message to a moderator |
|
|
|
| Re: Towing Gearing [message #354630 is a reply to message #354549] |
Mon, 11 May 2020 20:43 |
6cuda6
Messages: 975
Registered: June 2019
Karma: -6
|
Senior Member |
|
|
I dont tow anything and it sounds like i need to replace my final drive gears.... gotta find me a set of used ones.
Rich Mondor,
Brockville, ON
77 Hughes 2600
|
|
|
|
| Re: Towing Gearing [message #354631 is a reply to message #354549] |
Mon, 11 May 2020 21:12 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
|
Senior Member |
|
|
I have towed with the stock 3.07 gears and with the current 3.70 limited slip. I generally cruise somewhere between 60 and 65 mph. I try not to be in too much of a hurry anyway, and the gas mileage seems to be better the slower I go (within practical limits).
I use my second gear less with the 3.70 than with the original, and it comes off the line a bit quicker. I tow a 2003 Tracker at just under 3000# just about everywhere and make an annual 52o mile trip to the dunes towing my '53 Willys Jeep on a trailer, sometimes with a Honda Odyssey ATV thrown on for good measure. I estimate that load at 4000# - 4500#.
I also live and do most of my traveling in the West. My vacuum gauge is constantly varying from 2 in to 22 in of vacuum. Lots of ups and downs. An 8% grade is not unusual for several miles at a time. I really like the 3.70 for the above reasons.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
|
|
|
|
| Re: Towing Gearing [message #354641 is a reply to message #354549] |
Tue, 12 May 2020 10:00 |
kingd
Messages: 592
Registered: June 2004
Karma: 2
|
Senior Member |
|
|
Rich M, re changing final drive ratio in your GMC Motorhome. I know you were a GM dealer mechanic so you
would know more about ring and pinions than the average guy.(not the knowledgeable people on here)
Because of the set up on the MH, there is/was a way of changing drive ratios(sort off) via the chain.
There were a couple of sources for the sprockets and chain, and it sounds less complicated than doing the
diff, unless you can get another diff/final drive assembly. Another way is to check the scrap yards for on of
the GM cars that came with the 3.21:1 . Front wheel drive something old.
Does any one have an extra chain or gears or complete final drive to offer to Rich ? I know Jim K offers this
assembly with brand new gears and different ratios but shipping from California to Ontario Canada could be a deal
breaker.
DAVE KING
lurker, wannabe
Toronto, Ontario, Canada
|
|
|
|
| Re: [GMCnet] Towing Gearing [message #354643 is a reply to message #354641] |
Tue, 12 May 2020 10:29 |
powwerjon
Messages: 849
Registered: March 2013
Karma: -2
|
Senior Member |
|
|
Dave,
There are several chain drive setups available depending on the sprocket size and chain length. The only one that I am aware of that is still available is from Manny which is a 3.50 ratio chain drive setup. There was a I think were a 3.42ish and a 3.70ish setups available from one of the Heritage Cruiser in Canada. I talked to him last spring and he was not making anymore assemblies at that time so that make Manny’s the only game in tow as a complete kit.
In our first coach a 77 Eleganza II with a 403 I put a 3.55 gear from Jim K and it was a great wakeup for the 403 and got it into the rpm range that worked. I could run with any 455 out there. The present coach that we now have is a 29.5’ Buskirk stretch with a 461 Jasper RV motor, with Accel Gen 6 MPFI and a 3.67 drive ratio which feature a 3.21 final drive and a 3.50 Manny chain drive assy. In all setups we use the 225 tire to take max use of the final drive ratio. The coach is fast and pulls the hills and mountains and we have used it going to Tucson from Michigan from 2011 to 2018. We don’t used for the trip any longer as it had to sit in the sun and it was hard on the paint, we drive by car.
J.R. Wright
GMC Great Laker MHC
GMCGL Tech Editor
GMC Eastern States Charter Member
GMCMI
78 GMC Buskirk 29.5’ Stretch
75 GMC Avion (Under Reconstruction)
Michigan
Home again!
> On May 12, 2020, at 11:00 AM, Dave King via Gmclist wrote:
>
> Rich M, re changing final drive ratio in your GMC Motorhome. I know you were a GM dealer mechanic so you
> would know more about ring and pinions than the average guy.(not the knowledgeable people on here)
> Because of the set up on the MH, there is/was a way of changing drive ratios(sort off) via the chain.
> There were a couple of sources for the sprockets and chain, and it sounds less complicated than doing the
> diff, unless you can get another diff/final drive assembly. Another way is to check the scrap yards for on of
> the GM cars that came with the 3.21:1 . Front wheel drive something old.
>
> Does any one have an extra chain or gears or complete final drive to offer to Rich ? I know Jim K offers this
> assembly with brand new gears and different ratios but shipping from California to Ontario Canada could be a deal
> breaker.
> --
> DAVE KING
> lurker, wannabe
> Toronto, Ontario, Canada
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
|
|
|
|
| Re: Towing Gearing [message #354644 is a reply to message #354641] |
Tue, 12 May 2020 11:28 |
6cuda6
Messages: 975
Registered: June 2019
Karma: -6
|
Senior Member |
|
|
Although i've never do it personally it looks like just simply dropping the rear trany cover and swapping the chain/gears doesnt look possible with the trans in the coach as it looks like the first cross member is in the way [pictures look like it at least]. I would be open to a chain/gear swap....has anyone done just that and in the coach to boot?
kingd wrote on Tue, 12 May 2020 11:00Rich M, re changing final drive ratio in your GMC Motorhome. I know you were a GM dealer mechanic so you
would know more about ring and pinions than the average guy.(not the knowledgeable people on here)
Because of the set up on the MH, there is/was a way of changing drive ratios(sort off) via the chain.
There were a couple of sources for the sprockets and chain, and it sounds less complicated than doing the
diff, unless you can get another diff/final drive assembly. Another way is to check the scrap yards for on of
the GM cars that came with the 3.21:1 . Front wheel drive something old.
Does any one have an extra chain or gears or complete final drive to offer to Rich ? I know Jim K offers this
assembly with brand new gears and different ratios but shipping from California to Ontario Canada could be a deal
breaker.
Rich Mondor,
Brockville, ON
77 Hughes 2600
|
|
|
|
|
|
| Re: [GMCnet] Towing Gearing [message #354648 is a reply to message #354644] |
Tue, 12 May 2020 12:23 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
It IS necessary to remove the transmission from the coach in order to swap
the chain. With that proviso, it's a very simple change, but one MUST be
very careful to properly seat the spring clips which retain the two chain
sprockets on their hubs -- if a clip breaks or is not properly installed
and comes loose, the sprocket will move aft until it contacts the chain
cover, creating an awful racket & metal filings. Jerry Work, Manny, and I
have a campfire tale about that! :-)
I installed the 3.50 Caspro chain drive (now Manny's) right after I bought
my GMC in '98. I was VERY happy with it. In never shared the qualms some
have about the additional torque loads it imposes on the transmission --
too many high-torque Cadillac engines (including my own) have been run
satisfactorily for me to worry about that.
Ken H.
On Tue, May 12, 2020 at 12:29 PM 6cuda6--- via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Although i've never do it personally it looks like just simply dropping
> the rear trany cover and swapping the chain/gears doesnt look possible with
> the trans in the coach as it looks like the first cross member is in the
> way [pictures look like it at least]. I would be open to a chain/gear
> swap....has anyone done just that and in the coach to boot?
>
> kingd wrote on Tue, 12 May 2020 11:00
>> Rich M, re changing final drive ratio in your GMC Motorhome. I know you
> were a GM dealer mechanic so you
>> would know more about ring and pinions than the average guy.(not the
> knowledgeable people on here)
>> Because of the set up on the MH, there is/was a way of changing drive
> ratios(sort off) via the chain.
>> There were a couple of sources for the sprockets and chain, and it
> sounds less complicated than doing the
>> diff, unless you can get another diff/final drive assembly. Another way
> is to check the scrap yards for on of
>> the GM cars that came with the 3.21:1 . Front wheel drive something old.
>>
>> Does any one have an extra chain or gears or complete final drive to
> offer to Rich ? I know Jim K offers this
>> assembly with brand new gears and different ratios but shipping from
> California to Ontario Canada could be a deal
>> breaker.
>
>
> --
> Rich Mondor,
>
> Brockville, ON
>
> 77 Hughes 2600
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
|
|
| Re: [GMCnet] Towing Gearing [message #354665 is a reply to message #354664] |
Tue, 12 May 2020 23:49 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
|
Senior Member |
|
|
Grant, GM did have the 3.42 on the drawing board with the 3.54.
Our 3.55 is the same, just an engineers rounding the numbers.
In 1990 Marvin Peck ( Gear Master) encouraged me to start doing a 3.70
ratio.
Only reason why we still carry the 3.55 is for people that think a 200rpm
makes a difference in noise.
Oh, we have a person in Michigan that assemble units for us.
We know from our customers that the lower gears DO NOT hurt the Gas Mileage.
I have been running a 4.10 for the last 70,000 miles with my 403. I still
drive it 75-80mph.
There are several running the 4.10 and like it when they are driving 55mph.
On Tue, May 12, 2020 at 9:15 PM Grant Schaffer via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I am in a quandary with a 3.55 or a 3.70. I have always thought the 3.70
> would be better especially towing. If a 5000 pound load weather a toad or
> trailer will be fine with a 3.55 then maybe the Miles Per hour is a better
> trade off? Now if one wants to make a bet with heir buddies to put money on
> a burn out in a 12,000 pound coach then certainly the 3.7 or 4.1 is the
> definate gear set. My hesitance is not being happy with the 3.55 or the
> 3.7.
>
> Anything above 65 in with the 3.70 will be above 2800 rpms an thus engine
> noise. I would suggest with my new rebuild and now adding fuel injection,
> the 3.55 may be the better deal. plus if you would like to go 70 MPH and
> keep the rpms down would also be good. Has anyone looked into the
> transmission and if the 3.55 is more favorable that the 3.70 for shifting
> or heat?
>
> I remember reading a article with GMCI 1995 I think, about the 3.42 that
> was originally designed by GM but of course took 20 years to finally come to
> fruition was designed for our coaches, so I would think that the 3.55
> would be better?
>
> Thanks
> Grant
> --
> 1974 GMC Sequoia 26'
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
|
|
|
|
| Re: [GMCnet] Towing Gearing [message #354668 is a reply to message #354665] |
Wed, 13 May 2020 00:27 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
|
|
I have a 1969 Dodge P.U. that was sold as a Camper Special. It came factory
equipped with a 383 cu.in. engine, a 3 speed heavy duty torqueflite
automatic transmission, and a 4:10 differential. Factory dual exhaust, etc.
The first original engine ran 211,000 miles until the pre-ignition and
detonation caused by the reformulated unleaded gasoline. I drove it 70 mph
whenever I was on the road with the 10 foot open road camper. Didn't notice
excessive engine noise with it, even with the 4:10 gears. Before the
gasoline was reformulated, I consistently got 10 mpg. Never better than 8
afterwards. Still got that truck, but it doesn't see much use these days.
Approaching 300,000 miles.
Jim Hupy
Salem, Oregon
On Tue, May 12, 2020, 9:50 PM Jim Kanomata via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Grant, GM did have the 3.42 on the drawing board with the 3.54.
> Our 3.55 is the same, just an engineers rounding the numbers.
> In 1990 Marvin Peck ( Gear Master) encouraged me to start doing a 3.70
> ratio.
> Only reason why we still carry the 3.55 is for people that think a 200rpm
> makes a difference in noise.
> Oh, we have a person in Michigan that assemble units for us.
> We know from our customers that the lower gears DO NOT hurt the Gas
> Mileage.
> I have been running a 4.10 for the last 70,000 miles with my 403. I still
> drive it 75-80mph.
> There are several running the 4.10 and like it when they are driving 55mph.
>
> On Tue, May 12, 2020 at 9:15 PM Grant Schaffer via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> I am in a quandary with a 3.55 or a 3.70. I have always thought the 3.70
>> would be better especially towing. If a 5000 pound load weather a toad or
>> trailer will be fine with a 3.55 then maybe the Miles Per hour is a
> better
>> trade off? Now if one wants to make a bet with heir buddies to put money
> on
>> a burn out in a 12,000 pound coach then certainly the 3.7 or 4.1 is the
>> definate gear set. My hesitance is not being happy with the 3.55 or the
>> 3.7.
>>
>> Anything above 65 in with the 3.70 will be above 2800 rpms an thus engine
>> noise. I would suggest with my new rebuild and now adding fuel injection,
>> the 3.55 may be the better deal. plus if you would like to go 70 MPH and
>> keep the rpms down would also be good. Has anyone looked into the
>> transmission and if the 3.55 is more favorable that the 3.70 for shifting
>> or heat?
>>
>> I remember reading a article with GMCI 1995 I think, about the 3.42 that
>> was originally designed by GM but of course took 20 years to finally
> come to
>> fruition was designed for our coaches, so I would think that the 3.55
>> would be better?
>>
>> Thanks
>> Grant
>> --
>> 1974 GMC Sequoia 26'
>>
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>
>
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk@appliedairfilters.com
> http://www.gmcrvparts.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
|
|
|
|
| Re: [GMCnet] Towing Gearing [message #354670 is a reply to message #354668] |
Wed, 13 May 2020 06:07 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
Except for the trip most of the way home after buying the GMC, I've run the
3.50 chain or Jim K's 3.55 gear set. I run at the speed limit, whatever it
is (despite many follower claims of higher). I've been from Key West, FL
to Fairbanks, AK, always towing a Honda CRV, without finding any hill that
needed below 2nd gear. I've never felt underpowered (that was NOT the
reason for the "'cause I can" installation of the Cad500). If I had a 26'
rather than my 23', I'd go with Jim K's 3.70 gear set to compensate for the
additional weight.
Ken H.
On Wed, May 13, 2020 at 1:35 AM James Hupy via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I have a 1969 Dodge P.U. that was sold as a Camper Special. It came factory
> equipped with a 383 cu.in. engine, a 3 speed heavy duty torqueflite
> automatic transmission, and a 4:10 differential. Factory dual exhaust, etc.
> The first original engine ran 211,000 miles until the pre-ignition and
> detonation caused by the reformulated unleaded gasoline. I drove it 70 mph
> whenever I was on the road with the 10 foot open road camper. Didn't notice
> excessive engine noise with it, even with the 4:10 gears. Before the
> gasoline was reformulated, I consistently got 10 mpg. Never better than 8
> afterwards. Still got that truck, but it doesn't see much use these days.
> Approaching 300,000 miles.
> Jim Hupy
> Salem, Oregon
>
> On Tue, May 12, 2020, 9:50 PM Jim Kanomata via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> Grant, GM did have the 3.42 on the drawing board with the 3.54.
>> Our 3.55 is the same, just an engineers rounding the numbers.
>> In 1990 Marvin Peck ( Gear Master) encouraged me to start doing a 3.70
>> ratio.
>> Only reason why we still carry the 3.55 is for people that think a 200rpm
>> makes a difference in noise.
>> Oh, we have a person in Michigan that assemble units for us.
>> We know from our customers that the lower gears DO NOT hurt the Gas
>> Mileage.
>> I have been running a 4.10 for the last 70,000 miles with my 403. I still
>> drive it 75-80mph.
>> There are several running the 4.10 and like it when they are driving
> 55mph.
>>
>> On Tue, May 12, 2020 at 9:15 PM Grant Schaffer via Gmclist > gmclist@list.gmcnet.org> wrote:
>>
>>> I am in a quandary with a 3.55 or a 3.70. I have always thought the
> 3.70
>>> would be better especially towing. If a 5000 pound load weather a toad
> or
>>> trailer will be fine with a 3.55 then maybe the Miles Per hour is a
>> better
>>> trade off? Now if one wants to make a bet with heir buddies to put
> money
>> on
>>> a burn out in a 12,000 pound coach then certainly the 3.7 or 4.1 is the
>>> definate gear set. My hesitance is not being happy with the 3.55 or the
>>> 3.7.
>>>
>>> Anything above 65 in with the 3.70 will be above 2800 rpms an thus
> engine
>>> noise. I would suggest with my new rebuild and now adding fuel
> injection,
>>> the 3.55 may be the better deal. plus if you would like to go 70 MPH
> and
>>> keep the rpms down would also be good. Has anyone looked into the
>>> transmission and if the 3.55 is more favorable that the 3.70 for
> shifting
>>> or heat?
>>>
>>> I remember reading a article with GMCI 1995 I think, about the 3.42
> that
>>> was originally designed by GM but of course took 20 years to finally
>> come to
>>> fruition was designed for our coaches, so I would think that the 3.55
>>> would be better?
>>>
>>> Thanks
>>> Grant
>>> --
>>> 1974 GMC Sequoia 26'
>>>
>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>>
>>
>> --
>> Jim Kanomata
>> Applied/GMC, Newark,CA
>> jimk@appliedairfilters.com
>> http://www.gmcrvparts.com
>> 1-800-752-7502
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
| Re: Towing Gearing [message #354675 is a reply to message #354549] |
Wed, 13 May 2020 10:42 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
|
Senior Member |
|
|
If you are going to be towing more then about 2500 lbs I’d go with the 3.70 differential . I used to tow a jet boat from your neck of the woods with 3.21 gears to the Colorado River (Blythe ) and it was good but towing a small car into the Sierra Nevada mountains a 3.70 gear set was a must have. The fuel mileage didn’t seem to change much and engine noise at 65 wasn’t a problem when you consider the extra performance. It is a real bummer if you are geared high and you are on a steep mountain grade towing your car in first gear and you don’t think you are going to make the top. This is what convinced me to get the 3.70 gears .
Roy Keen
Minden,NV
76 X Glenbrook
|
|
|
|
Goto Forum:
Current Time: Fri Sep 27 18:18:15 CDT 2024
Total time taken to generate the page: 0.01432 seconds
|
GMCforum
Search
Help
Register
Login
Home
.... quess i'll have to wait and see if anyone on this side of the river has a used final drive and/or final drive gear set for sale or live with what i have till i tear everything out for a rebuild some day.