Home » Public Forums » GMCnet » New Manny Tranny on hills (Question for Matt Colie re: engine "lugging")
| New Manny Tranny on hills [message #195317] |
Wed, 09 January 2013 20:03  |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
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Senior Member |
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Back in August I posted the following:
"Coach, 1976 Palm Beach has 455 w/carb and 3:70. coach weighs~11,000 lbs.
Northbound on I-5 between the Oregon border and Canyonville (about 100 miles) you encounter Siskiyou Summit 4310' (highest point on I-5) 7 miles of 6% grade on both sides,
Sexton Pass (named for GMCer Dennis Sexton?) 1960', Smith Hill Summit 1730', Stage Road Pass 1830', Canyon Creek Pass 2020' the approaches to each of these passes have one to three miles of 6% grade
All of these hills except Canyon Creek Pass required downshifting to second for part of the climb. .
When speed drops below 50 mph and rpm drops below 2500 and vacuum is 5" or less I manually shift to 2nd."
In early November my old tranny died and I installed a new Manny Tranny and have now driven it almost 2500 miles, including a trip from Red Bluff, Ca. to Hillsboro, Ore. and back over the above mentioned grades/passes.
With the new Manny Tranny the coach runs "stronger' feels "lighter", peppier, more responsive to the throttle. Not my imagination.
On the trip to Oregon with one exception the coach made all these grades without falling below below 48 mph or 2400 rpm in 3rd gear. So I didn't manually downshift
The exception was the southbound 7 mile 6% grade.
Near the top of the hill the tranny automattically downshifted to 2nd at about 42mph and 2200 rpm.
So the question for Matt Colie or any one else who knows is this: At what speed/rpm at WOT on a long uphill grade does "lugging" occur and become detrimental to the engine or transmission? Or: Given the ~2700 rpm most efficient power point for the 455, what is the lowest "safe" rpm for the engine/tranny under heavy load?
Any Oregon Netters want to report their experience over these passes?
Thanks to all for your input.
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
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| Re: New Manny Tranny on hills [message #195318 is a reply to message #195317] |
Wed, 09 January 2013 20:20  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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I'm not Matt, but I would think it better to be up around 3000 in that high load condition. Less torque converter heat build, better coolant and oil flow. I just towed long distance with my Tahoe pulling a U haul autotransporter with an S15 $WD on it. Now granted the 455 is a lot torqueier than an SB 350, but even with 3.73's, in OD the engine is at 2k at 65MPH and making little grunt. I found it best to shift manually down to D at the start of each rolling hill, thereby skipping the lock / unlock cycle on the wimpy convert lockup clutch and requiring LESS throttle to make the grade. That put me at about 3K and I would then regain lost speed and the engine was happier.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: New Manny Tranny on hills [message #195320 is a reply to message #195317] |
Wed, 09 January 2013 20:45 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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| gbarrow wrote on Wed, 09 January 2013 18:03 |
...
At what speed/rpm at WOT on a long uphill grade does "lugging" occur and become detrimental to the engine or transmission? Or: Given the ~2700 rpm most efficient power point for the 455, what is the lowest "safe" rpm for the engine/tranny under heavy load?
...
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I also would like to know what the experts have to say. I downshift manually to keep the RPM's up. But I am using a 403 with stock final drive.
I would like numbers for both the 455 and 403 motors.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: New Manny Tranny on hills [message #195322 is a reply to message #195318] |
Wed, 09 January 2013 20:54 |
John Sharpe
Messages: 489
Registered: February 2006
Location: Texas
Karma: 1
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| Quote: |
..... At what speed/rpm at WOT on a long uphill grade does "lugging" occur and become detrimental to the engine or transmission?........
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I'm not an engineer. But generally on here, the number 2500 rpm in 3rd on an uphill climb is said to be close to the lower limit. Of course you are running a 3.70 so your lugging problem would be a lot different that those of us running 3.07's
John Sharpe
Humble,TX
'78 Eleganza TBI
'89 Spectrum 2000 MPI V-10
'40 Ford Panel Delivery TPI
johnasharpe@gmail.com
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| Re: [GMCnet] New Manny Tranny on hills [message #195323 is a reply to message #195317] |
Wed, 09 January 2013 20:50 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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It has been my personal experience, also with a stock transmission with
3:07 final drive and a 403 with high mileage on those very same hills in
both summer and winter to downshift manually at 50 mph. My coach is a 78
Royale by Coachman and it weighs 11,000 and change. The 403 would pull down
to about 38 to 40 mph on those passes. When my transmission gave up the
ghost, I sprung for a Manny Transmission and at the same time installed Jim
K.'s 3:70 final drive gears. I have since pulled those same passes both
summer and winter both directions. The first trip I was extremely careful
because I had just installed the trans. the night before we left, and the
final drive was not broken in. The last trip was in November for the 49 ers
rally in Red Bluff. I also ran some 13% upgrades both uphill and downhill
in Canada. I can pull those passes in Oregon in high gear with the present
combination. The 13% stuff, 17 mph in first gear, running about 10 " of
vacuum to stay out of the secondaries. To address the lugging question, if
the rpm of the engine is below the stall speed of the torque converter, you
will have a greater problem with overheating the transmission than you will
with engine damage. Don't be afraid to rev the engine to 3200 or so,
especially if it is a 403. You won't hurt a good engine at that rpm.
JimHupy
Salem, Or
78 Gmc Royale 403
On Jan 9, 2013 6:03 PM, "gene barrow" <barrowgene@gmail.com> wrote:
>
>
>
>
> Back in August I posted the following:
>
> "Coach, 1976 Palm Beach has 455 w/carb and 3:70. coach weighs~11,000 lbs.
>
> Northbound on I-5 between the Oregon border and Canyonville (about 100
> miles) you encounter Siskiyou Summit 4310' (highest point on I-5) 7 miles
> of 6% grade on both sides,
>
> Sexton Pass (named for GMCer Dennis Sexton?) 1960', Smith Hill Summit
> 1730', Stage Road Pass 1830', Canyon Creek Pass 2020' the approaches to
> each of these passes have one to three miles of 6% grade
>
> All of these hills except Canyon Creek Pass required downshifting to
> second for part of the climb. .
>
> When speed drops below 50 mph and rpm drops below 2500 and vacuum is 5" or
> less I manually shift to 2nd."
>
>
> In early November my old tranny died and I installed a new Manny Tranny
> and have now driven it almost 2500 miles, including a trip from Red Bluff,
> Ca. to Hillsboro, Ore. and back over the above mentioned grades/passes.
>
>
> With the new Manny Tranny the coach runs "stronger' feels "lighter",
> peppier, more responsive to the throttle. Not my imagination.
>
>
> On the trip to Oregon with one exception the coach made all these grades
> without falling below below 48 mph or 2400 rpm in 3rd gear. So I didn't
> manually downshift
>
> The exception was the southbound 7 mile 6% grade.
>
> Near the top of the hill the tranny automattically downshifted to 2nd at
> about 42mph and 2200 rpm.
>
>
> So the question for Matt Colie or any one else who knows is this: At what
> speed/rpm at WOT on a long uphill grade does "lugging" occur and become
> detrimental to the engine or transmission? Or: Given the ~2700 rpm most
> efficient power point for the 455, what is the lowest "safe" rpm for the
> engine/tranny under heavy load?
>
> Any Oregon Netters want to report their experience over these passes?
>
> Thanks to all for your input.
>
>
> --
> Gene Barrow
> Lake Almanor, Ca.
> 1976 Palm Beach
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>
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| Re: New Manny Tranny on hills [message #195328 is a reply to message #195321] |
Thu, 10 January 2013 00:23 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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Senior Member |
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| robertmcw wrote on Wed, 09 January 2013 18:49 |
Would a Variable pitch converter (creates a 6-speed transmission.) help in the mountains?
Robert
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I have the switch-pitch and it is indeed handy. One of the good features is that the "regular, not switched" stall is lower than the original torque converter. Our stock converters have a stall of about 2200. (Lock the brake and step on it and the RPMs go to 2200.) When not switched mine is more like 1700 RMPs.
When I switch the converter the stall is more like 2600+. This can jump you back onto a good torque range without shifting. The thing to remember is automatic transmissions have cooling lines in the radiator for one reason. Torque converters produce a ton of heat because they slip. The more they slip the more heat is produced. I never keep my trans in switch for more than a minute or two. I have never seen the heat going up quickly but I also know it is way hotter in the torque converter than in the pan and there is probably a lag between real heat and the gauge.
When I have a tough hill, I like to run my 455 between 2700 and 3200. It is a good engine and seems to pull well in that range. At that RPM I know the converter (not switched) is about as locked up as it will get. But it is slipping. Hills make the temp go up.
Lug an original converter down to 2100 and it is beginning to slip big time. Trans heat will follow. Run it at 2100 on a hill long enough and I think you will be looking at a new transmission. It just cannot dump the heat quick enough.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: New Manny Tranny on hills [message #195339 is a reply to message #195317] |
Thu, 10 January 2013 09:36 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| gbarrow wrote on Wed, 09 January 2013 21:03 |
Back in August I posted the following:
"Coach, 1976 Palm Beach has 455 w/carb and 3:70. coach weighs~11,000 lbs.
Northbound on I-5 between the Oregon border and Canyonville (about 100 miles) you encounter Siskiyou Summit 4310' (highest point on I-5) 7 miles of 6% grade on both sides,
Sexton Pass (named for GMCer Dennis Sexton?) 1960', Smith Hill Summit 1730', Stage Road Pass 1830', Canyon Creek Pass 2020' the approaches to each of these passes have one to three miles of 6% grade
All of these hills except Canyon Creek Pass required downshifting to second for part of the climb. .
When speed drops below 50 mph and rpm drops below 2500 and vacuum is 5" or less I manually shift to 2nd."
In early November my old tranny died and I installed a new Manny Tranny and have now driven it almost 2500 miles, including a trip from Red Bluff, Ca. to Hillsboro, Ore. and back over the above mentioned grades/passes.
With the new Manny Tranny the coach runs "stronger' feels "lighter", peppier, more responsive to the throttle. Not my imagination.
On the trip to Oregon with one exception the coach made all these grades without falling below below 48 mph or 2400 rpm in 3rd gear. So I didn't manually downshift
The exception was the southbound 7 mile 6% grade.
Near the top of the hill the tranny automatically downshifted to 2nd at about 42mph and 2200 rpm.
So the question for Matt Colie or any one else who knows is this: At what speed/rpm at WOT on a long uphill grade does "lugging" occur and become detrimental to the engine or transmission? Or: Given the ~2700 rpm most efficient power point for the 455, what is the lowest "safe" rpm for the engine/tranny under heavy load?
Any Oregon Netters want to report their experience over these passes?
Thanks to all for your input.
|
Gene,
First I have to say that most of what has gone by is correct. The fact that you have a 3.70 is really not going to change much in a real sense, but your road speeds will be much more real world than most. In the current world 3.07 is just plain wrong.
Executive Summary:
Pull it down to stay out of the secondaries and you will be alright. If you get near 4K, let it back up.
George's remark that the torque converter is a big part of the issue is very correct. And that stall test is something you should do. (It takes 30 seconds the next time the engine is well warmed up.) Avoiding running below stall is quite important. With a 3.07, this can be tough. Mine is right there at 60MPH.
Generally speaking, it is tough to lug an engine into a damaging region with the calibration of most automatic transmissions. It is true that you do not want to go into the secondaries if you can avoid it for two reasons, the first is straight economy - the secondaries are usually set up for rich for max power and second is that this calibration is not intended for extended operation. (We used to call it WOT-ZOOM mode.)
The "automatic" downshift happens one of two ways, either the "kick-down" switch attached to the throttle linkage or the vacuum modulator. I am told that neither is the best mode and manually pulling the transmission down is a far better way to get things in the correct band.
If we can get back to the engine speeds and related things, let me start by saying that I very little real data to work from here. I have to go the power curve data that I have seen and that indicates a in the 24~2600RPM region for both the 455 and 403. With the torque converter going start to slip (mine starts a ~2K) and with real lugging probably down below 1500 range, there is just no reason at all to run the engine at those speeds. While the timing is still on the centrifugal advance, there is no bet that it is close to best at this load.
Damage from lugging an occurs two ways, either from the fuel/spark calibration being way out for the load/speed or the cylinder pressure being too high for the bearings to work correctly. With the 455, the later is just not going to be an issue. The relatively large bearing for the class is why this was a preferred industrial conversion for many years. But mixture and timing are another bet. If you are climbing and you hear it cackle, back out and pull it down to second right then.
There a lot here, and I hope the questions were answered. If not, well I'm here a lot. (When I am not in/under the coach.)
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: New Manny Tranny on hills [message #195346 is a reply to message #195317] |
Thu, 10 January 2013 11:15 |
Darryl
Messages: 144
Registered: December 2011
Location: Northern California
Karma: 0
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Senior Member |
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I run a 403 with the 3.07 FD and no tach. I've been downshifting to second at 40mph on hills but I'm thinking I should be shifting at 50 instead. Anyone know what the rpm's would be at 50 in second?
Darryl Meyers
1978 Eleganza II
El Dorado Hills, CA
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| Re: New Manny Tranny on hills [message #195356 is a reply to message #195317] |
Thu, 10 January 2013 15:14 |
Darryl
Messages: 144
Registered: December 2011
Location: Northern California
Karma: 0
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Senior Member |
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Thanks, Jim. I'll start downshifting at 48-50. I was concerned about keeping the engine below 4k but it sounds like it's turning less than 3500 at 50.
A 3:70 is on the list but Jim K. is spending a bunch of my money this week on new front wheel bearings, new fuel lines, an A/C compressor and a list of other expensive stuff. Maybe next year.
Darryl Meyers
1978 Eleganza II
El Dorado Hills, CA
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| Re: [GMCnet] New Manny Tranny on hills [message #195357 is a reply to message #195355] |
Thu, 10 January 2013 15:14 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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I can run 75 mph and not overrev my 403. It is less than 3600 rpm with the
3:70 final drive at that speed. I consistently run in the 3200-3400 rpm
range when travelling. The 403 seems to be really happy at that rpm. If I
am not bucking headwinds, I consistently get better than 10 miles per
gallon.
Jim Hupy
Salem, Or
78 Gmc Royale 403
On Jan 10, 2013 12:53 PM, "A." <markbb1@netzero.com> wrote:
>
>
> James Hupy wrote on Thu, 10 January 2013 14:48
> > Darryl, given the 403's lack of torque below 48-50 mph, I usually
> manually downshift at about that speed if the top of the upgrade is not in
> sight.
> > But with the 3:70 final drive gears, my 403 will not lose speed on
> anything less than a 6% grade. It is the best performance upgrade that you
> can make for the money spent.
> > Jim Hupy
> > Salem, Or
> > 78 Gmc Royale 403
> What we need is a two-speed FD. One ratio for climing hills and another
> for flatland with a tailwind.
> --
> '73 23' Sequoia
> UA (Upper Alabama)
> "Time is money. If you use YOUR time, you get to keep YOUR money."
> _______________________________________________
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| Re: [GMCnet] New Manny Tranny on hills [message #195363 is a reply to message #195362] |
Thu, 10 January 2013 16:27 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
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The price is higher now than shown at that site,
but JimK's price beats that on the manufacturer's
website and in stock! I got one a three weeks ago.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~ ~ ~ ~ TZE166V101966 ~ ~ ~ ~
~ ~ ~ '76 ex-Palm Beach ~ ~ ~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
______________
*[ ]~~~[][ ][|\
*--OO--[]---O-*
> Date: Thu, 10 Jan 2013 14:18:35 -0800
> From: mr.erfisher@gmail.com
> To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] New Manny Tranny on hills
>
> this could help
> http://www.gmcmotorhome.com/tech/tachvac/index.html
>
> gene
>
>
> On Thu, Jan 10, 2013 at 1:14 PM, Darryl Meyers <hospacctg@att.net> wrote:
>
> >
> >
> > Thanks, Jim. I'll start downshifting at 48-50. I was concerned about
> > keeping the engine below 4k but it sounds like it's turning less than 3500
> > at 50.
> >
> > A 3:70 is on the list but Jim K. is spending a bunch of my money this week
> > on new front wheel bearings, new fuel lines, an A/C compressor and a list
> > of other expensive stuff. Maybe next year.
> > --
> > Darryl Meyers
> >
> > 1978 Eleganza II
> >
> > El Dorado Hills, CA
> > _______________________________________________
> >
>
> --
> Gene Fisher -- 74-23,77PB/ore/ca
> “Give a man a fish; you have fed him for today --- give him a URL and
> -------
> http://gmcmotorhome.info/
> Alternator Protection Cable
> http://gmcmotorhome.info/APC.html
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| Re: New Manny Tranny on hills [message #195370 is a reply to message #195356] |
Thu, 10 January 2013 19:26 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| Darryl wrote on Thu, 10 January 2013 16:14 |
Thanks, Jim. I'll start downshifting at 48-50. I was concerned about keeping the engine below 4k but it sounds like it's turning less than 3500 at 50.
A 3:70 is on the list but Jim K. is spending a bunch of my money this week on new front wheel bearings, new fuel lines, an A/C compressor and a list of other expensive stuff. Maybe next year.
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Darryl,
Don't spend much, get one of these from EvilBay (290606353066). It sure is nothing like the Tach-Vac (I would love to have), but for 26$us and about an half an hour you have a working and reliable tachometer.
Then, when you get through with the other stuff - get the Tach-Vac.
Matt - maybe never be though with the other stuff.
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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