| GMC’s transmission [message #360310] |
Thu, 26 November 2020 14:56  |
tgeiger
Messages: 518
Registered: February 2006
Location: kansas city
Karma: -1
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Senior Member |
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Happy Thanksgiving all! Hope all is well for our GMC community. While the bird is cooking was think of what task I can get done this weekend on mine. Been doing some researching and ran across a posting outside the GMC forum pertaining to the 454 engine. That pre-1990 454 trucks had horrible gas mileage because of a lack of a overdrive. It just brought to mind our transmission. Is it impossible to create the adaptor plates to mod our transmission to a Allison 6 speed or is this down right crazy talk? I get to ask these kind of questions because I know nothing of transmissions. Anyhow I’m sure there are good reasons not to, just curious of what they are?
Thanks,
TG
Tom Geiger
76 Eleganza II
KCMO
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| Re: [GMCnet] GMC’s transmission [message #360311 is a reply to message #360310] |
Thu, 26 November 2020 15:11  |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Man o' man, I have much to be thankful for, this Thanksgiving. Thinking of
all my met and unmet as of yet GMC friends. There are so many of you in
Australia and New Zealand, and every province of Canada, the U.S.A. and
Europe. You guys, and Ladies know who you are. The list is long.
And I cannot leave out my biological family, and the new one by
marriage, too.
Judy is doing extremely well with her replacement knee. I still am on the
green side of dirt. Like I said, much to give thanks for. But, I want a
"mulligan" on 2020. It sucks.
Jim Hupy, JBH Products
Salem. Oregon
1978 GMC Royale by Coachman.
Hasn't seen much use this year. 2021 has to be better.
On Thu, Nov 26, 2020, 12:57 PM tom geiger via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Happy Thanksgiving all! Hope all is well for our GMC community. While the
> bird is cooking was think of what task I can get done this weekend on mine.
> Been doing some researching and ran across a posting outside the GMC forum
> pertaining to the 454 engine. That pre-1990 454 trucks had horrible gas
> mileage because of a lack of a overdrive. It just brought to mind our
> transmission. Is it impossible to create the adaptor plates to mod our
> transmission to a Allison 6 speed or is this down right crazy talk? I get
> to ask these kind of questions because I know nothing of transmissions.
> Anyhow I’m sure there are good reasons not to, just curious of what they
> are?
>
> Thanks,
> TG
> --
> Tom Geiger
> 76 Eleganza II
> KCMO
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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| Re: GMC’s transmission [message #360312 is a reply to message #360310] |
Thu, 26 November 2020 16:09 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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Senior Member |
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There's not really a practical way to adapt another trans in the GMC FWD application. Allison's are great units but huge and never built in a configuration that would work. There is a GMCer that has worked on building an overdrive TH425 but bringing it to market would be a huge expense and more money than could be reasonably justified.
I used a 4l80e which is basically a TH400 with .75 overdrive but in a totally different configuration that few would try to duplicate.
Optimizing your gear ratio would seem to be the direction to go IMHO.
Hal
tgeiger wrote on Thu, 26 November 2020 13:56Happy Thanksgiving all! Hope all is well for our GMC community. While the bird is cooking was think of what task I can get done this weekend on mine. Been doing some researching and ran across a posting outside the GMC forum pertaining to the 454 engine. That pre-1990 454 trucks had horrible gas mileage because of a lack of a overdrive. It just brought to mind our transmission. Is it impossible to create the adaptor plates to mod our transmission to a Allison 6 speed or is this down right crazy talk? I get to ask these kind of questions because I know nothing of transmissions. Anyhow I’m sure there are good reasons not to, just curious of what they are?
Thanks,
TG
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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