Home » Public Forums » GMCnet » [GMCnet] Power Drive
[GMCnet] Power Drive [message #86635] |
Sun, 30 May 2010 16:33 |
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USAussie
Messages: 15912 Registered: July 2007 Location: Sydney, Australia
Karma: 6
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Senior Member |
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G'day,
I have a 3.21 FD to install in Double Trouble and am considering installing
one of these:
http://www.casprogmc.net/powerDrive.html
I vaguely remember reading that there is a down side to these unit over the
lower ratio final drive units sold by Jim K but CRS has erased that
recollection. I went through my transmission and final drive folders but
found NADA.
What's the advantages / disadvantages of Power Drive vs. lower final drive
ratios?
Also I vaguely remember that Manny took over from Caspro, did I get that
right?
Thanks,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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Re: [GMCnet] Power Drive [message #86640 is a reply to message #86638] |
Sun, 30 May 2010 17:11 |
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USAussie
Messages: 15912 Registered: July 2007 Location: Sydney, Australia
Karma: 6
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Guys,
I just did a search of the Forum and found lots of info on the power drive.
DOUH!
Nothing grossly negative so I think I'll contact Manny OFF NET.
If someone has a nightmare story and doesn't want to post it send an email
to: robmueller at iinet dot net dot au.
Thanks,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Rob Mueller
Sent: Monday, 31 May 2010 7:56 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] Power Drive
Gene,
Yep, that's the one!
Now who's got one?
Thanks,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: Mr.erf ERFisher
you must mean this
http://www.casprogmc.net/powerDrive.html
gene
yep is manny
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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Re: [GMCnet] Power Drive [message #86642 is a reply to message #86635] |
Sun, 30 May 2010 17:44 |
Rick Williams
Messages: 256 Registered: July 2004
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Rob
I had one installed when I ordered a tranny from Manny about 8k miles ago. It has made a difference in just the same way as a final drive gear change. It added a couple hundred or so rpms and the coach has a bit more power in the hills. I was considering a final drive change when the original tranny failed so I opted for the power drive. I will be curious to see how yours performs if you do make the change. I have been considering changing the final drive to a 3.21 to get a bit more. I tow a Jeep Wrangler and it is about 3500 lbs. Big hills are still a struggle with the current setup and a stock 403.
I think Dave Lenzi removed his power drive and used a 3.21 when he installed his 8.1 engine. I do not remember his reason but I think he is pleased with the current setup.
Rick
Rick Williams
Bliss, Michigan
1978 Eleganza II
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Re: [GMCnet] Power Drive [message #86647 is a reply to message #86635] |
Sun, 30 May 2010 18:19 |
Ken Henderson
Messages: 8726 Registered: March 2004 Location: Americus, GA
Karma: 9
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Rob,
When I had to rebuild an engine for the GMC immediately after buying it in
'98, I had a r300 "bench overhaul" done on the transmission and installed
the Caspro Power Drive. That transmission and chain drive are now in the
X-PB my son has. I put about 63,000 miles on it before replacing it with
the new front clip; he's probably put another 5,000 mile on it. The rebuilt
torque converter failed after 10,000 miles (cracked around the hub, just
like JR Slaten's recent failure), but otherwise, there's never been any
problem whatsoever with the transmission or chain drive.
That was before JimK started selling high ratio final drives. If I had to
choose between the 3.50 chain and his 3.55 today, it would be a hard choice,
but if I had the transmission out anyway, I'd probably save the $$$ and go
with the chain.
At the time I installed my chain, they were still being distributed by Chuck
Stoddard's Caspro; Manny has now bought the rights and is selling them.
By the way, have you thoroughly investigated the 3.21 installation? A
Dixielander buddy recently bought one that we plan to install soon.
Discussing it with 3.21 experts was an eye-opener: It's not necessarily a
straight-forward, no potential problems, affair. Axle bearings & seals,
input bearing condition, etc., etc, all need attention. I'm sending you
some more info off-net.
Ken H.
Americus, GA
'76 X-Birchaven
www.gmcwipersetc.com
On Sun, May 30, 2010 at 5:33 PM, Rob Mueller <robmueller@iinet.net.au>wrote:
> G'day,
>
> I have a 3.21 FD to install in Double Trouble and am considering installing
> one of these:
>
> http://www.casprogmc.net/powerDrive.html
>
> I vaguely remember reading that there is a down side to these unit over the
> lower ratio final drive units sold by Jim K but CRS has erased that
> recollection. I went through my transmission and final drive folders but
> found NADA.
>
> What's the advantages / disadvantages of Power Drive vs. lower final drive
> ratios?
>
> Also I vaguely remember that Manny took over from Caspro, did I get that
> right?
>
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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Re: [GMCnet] Power Drive [message #86649 is a reply to message #86635] |
Sun, 30 May 2010 18:27 |
Chr$
Messages: 2690 Registered: January 2004 Location: Scottsdale, AZ
Karma: 1
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I have both. power drive and 3.21.
I don't have a tach, but the rpm's are definitely higher. A bit too high for my taste, but I haven't really spent any serious road time in my coach, so too early to tell. I'm also used to an overdrive tranny in my truck.
I am having a bit of irritation with the 3.21. The vent hole occasionally becomes a blow hole. It is intermittent which really annoys me. I'm told 3.21's don't have this vent and it is a 3.42. Everyone who looks at the photo's say it is a 3.21. go figure. It came with a '67 eldo switch pitch.
With this combo, I can burn a patch at every intersection if I so desire. sometimes do it unintentionally.
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
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Re: [GMCnet] Power Drive [message #86655 is a reply to message #86649] |
Mon, 31 May 2010 01:08 |
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USAussie
Messages: 15912 Registered: July 2007 Location: Sydney, Australia
Karma: 6
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Chris,
OK, here's what I think I know!
If the final drive cover has eight (8) bolts it is a 3.21 and it has
planetary gears in it.
If the final drive cover has ten (10) bolts it's a 3.07 and it has spur
gears in it.
As far as any other ratios goes I found this:
http://www.gmcmhphotos.com/photos/data/5124/overall_drive_ratios1.pdf
I thank Ken H. for putting this together!
Mr. Erf aren't you proud of me; I found this on your website WITHOUT you
having to tell me to go look there! ;-)
I think I am safe in saying any final drive gear ratios other than 2.73,
3.07 and 3.21 are after market.
I don't know but would like to know, if the lower ratio after market gears
will fit in the 3.21 final drive.
Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: Chris Choffat
I'm told 3.21's don't have this vent and it is a 3.42. Everyone who looks
at the photo's say it is a 3.21. go figure. It came with a '67 eldo switch
pitch.
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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Re: [GMCnet] Power Drive [message #86656 is a reply to message #86649] |
Mon, 31 May 2010 01:22 |
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USAussie
Messages: 15912 Registered: July 2007 Location: Sydney, Australia
Karma: 6
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Senior Member |
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Chris,
I missed one of your comments; according to Caspro the 3.21 and the Power
Drive results in a final drive ratio of 3.66 to 1
http://www.casprogmc.net/3.21FinalDrive.html
Jim K has a chart on his website noting that at 65 mph the rpm difference
between a stock 3.07 and 3.66 ratio is 485rpm:
http://www.appliedgmc.com/level.itml/icOid/482
Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: Chris Choffat
I have both. power drive and 3.21.
I don't have a tach, but the rpm's are definitely higher. A bit too high for
my taste, but I haven't really spent any serious road time in my coach, so
too early to tell. I'm also used to an overdrive tranny in my truck.
_______________________________________________
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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Re: [GMCnet] Power Drive [message #86710 is a reply to message #86635] |
Mon, 31 May 2010 15:09 |
zhagrieb
Messages: 676 Registered: August 2009 Location: Portland Oregon
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I've put about 13K on mine and love it. It has the same effect as changing the rear end ratio ie: allows the engine to work in a slightly higher RPM range where it produces more power. A minor drawback to the rear end change is the need to change the speedometer drive gear in order to retain accuracy. The power drive doesn't require this.
Glenn Giere
Glenn Giere, Portland OR, K7GAG
'73 "Moby the Motorhome" 26'
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Re: [GMCnet] Power Drive [message #86719 is a reply to message #86710] |
Mon, 31 May 2010 15:40 |
jimk
Messages: 6734 Registered: July 2006 Location: Belmont, CA
Karma: 9
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There is a difference in the method of reducing the gear ratio .
Doing it by the chain method is not uncommon, but the load ending up
on the transmission becomes greater as the transmission is still
turning at the same rate as before.
While doing the work at the final gear does not put any additional
load on the transmission.
Even Wes C. agrees on that .
Bottom line is to at least get the ratio lower to help overall
performance without consuming more fuel.
On Mon, May 31, 2010 at 1:09 PM, Glenn Giere <glenngiere@gmail.com> wrote:
>
>
> I've put about 13K on mine and love it. Â It has the same effect as changing the rear end ratio ie: allows the engine to work in a slightly higher RPM range where it produces more power. Â A minor drawback to the rear end change is the need to change the speedometer drive gear in order to retain accuracy. Â The power drive doesn't require this.
>
> Glenn Giere
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--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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1-800-752-7502
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Re: [GMCnet] Power Drive [message #86733 is a reply to message #86712] |
Mon, 31 May 2010 18:54 |
jimk
Messages: 6734 Registered: July 2006 Location: Belmont, CA
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Bruce,
Your expanation is very good. I can see why I was lucky to earn a
grade of C in college in technical writing when most of the class was
pulling A and B in that class.
Many people will argue that there is no problem using the chain drive
reduction method on the coaches, but people that have been working on
these for long time admit that it does stress some of the components
on the trans.
On Mon, May 31, 2010 at 2:01 PM, Bruce Hislop <bruce@perthcomm.com> wrote:
>
>
> The downside of the PowerDrive from what I can see... and read somewhere... is the increased torque developed by the changing the chain drive ratio has to be handled by the transmission as well.
>
> Whereas if you change the final drive, the torque handled by the tranny will be reduced in favour of slightly higher rpm's.
>
> True/false??
>
> --
> Bruce Hislop,
> S. Ontario Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI and ESC.
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
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Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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Re: [GMCnet] Power Drive [message #86754 is a reply to message #86733] |
Mon, 31 May 2010 21:25 |
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mike miller
Messages: 3576 Registered: February 2004 Location: Hillsboro, Oregon
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jimk wrote on Mon, 31 May 2010 16:54 | ...
Many people will argue that there is no problem using the
chain drive reduction method on the coaches, but people that
have been working on these for long time admit that it does
stress some of the components on the trans.
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Not a small thing when considering the weakest link in our drivetrain is the transmission.
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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