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Old 04-30-2009, 03:02 PM
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Th350 Tranny swap DRIVE SHAFT ISSUES

Just trying to weigh out my options here.
I have a 79 Trans Am that has a Th350 in it. Its the WORST TH350 of the bunch as its the Olds. bell housing style. I have put a 350 CHEBBY engine in the car and I required the TCI adapter plate so the block would mount properly to the tranny.

Its time to replace the tranny. I have a good buddy that has a very low miles TH 350 in a 81 chevy pick up that he's willing to sell me. The tail shaft on his tranny measures out to be a 9 inch. My original tranny has the 6 inch. Naturally my drive shaft won't work with his tranny.

So what are my options? I really don't want to cut and modify my drive shaft. I guess we could swap tail shafts however that may be more trouble then its worth as im almost positive that it requires dismantling the tranny from front to back to swap tails?

Since they did NOT make any TH350's with 9 inch tails for a 79 Bird is there any other drive shafts out there that I may get LUCKY and be a perfect fit for my application? Im NOT Sure what the 79 Monte's have regarding tail length?

Thanks for any and all replies
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Old 04-30-2009, 03:14 PM
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Quote:
Originally Posted by sugar ray
Just trying to weigh out my options here.
I have a 79 Trans Am that has a Th350 in it. Its the WORST TH350 of the bunch as its the Olds. bell housing style. I have put a 350 CHEBBY engine in the car and I required the TCI adapter plate so the block would mount properly to the tranny.

Its time to replace the tranny. I have a good buddy that has a very low miles TH 350 in a 81 chevy pick up that he's willing to sell me. The tail shaft on his tranny measures out to be a 9 inch. My original tranny has the 6 inch. Naturally my drive shaft won't work with his tranny.

So what are my options? I really don't want to cut and modify my drive shaft. I guess we could swap tail shafts however that may be more trouble then its worth as im almost positive that it requires dismantling the tranny from front to back to swap tails?

Since they did NOT make any TH350's with 9 inch tails for a 79 Bird is there any other drive shafts out there that I may get LUCKY and be a perfect fit for my application? Im NOT Sure what the 79 Monte's have regarding tail length?

Thanks for any and all replies

The difference is in the rear housing and the tail shaft lengths. You can take both apart and swap the tail shafts and parts attached thereto and rear housings and come out fine.

Bogie
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Old 04-30-2009, 03:44 PM
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Quote:
Originally Posted by sugar ray
So what are my options? I really don't want to cut and modify my drive shaft. I guess we could swap tail shafts however that may be more trouble then its worth as im almost positive that it requires dismantling the tranny from front to back to swap tails?
Cut and modify the driveshaft or disassemble the trans completely to swap the output shaft. You won't find a driveshaft that bolts in.
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Old 04-30-2009, 04:50 PM
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You might get lucky and find a shaft that fits, I have not had to cut a shaft in years, and I build 5 to 10 cars a year, It may be a Ford shaft, or AMC that fits, but it's pretty certain there is one out there. I have an AMC Marlin with a T350, and BBC in it with a Dodge Aspen driveshaft in it, and a chevy half ton with a stock front shaft, and a rear shaft out of a Gremlin. Whatever fits.
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Old 04-30-2009, 06:02 PM
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why dont you just get a 6" tail th350 ? i dont see any issue here at all.


good luck
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Old 04-30-2009, 07:38 PM
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thanks guys!

fast 68: the reason i just dont get a th350 with 6 inch length is because my buddy is willing to give me his good th350 for next to nothing
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Old 05-02-2009, 12:03 AM
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The 350 trannys are the same...only the tail shafts are different.


But the tailshaft is one of the first parts to go into the bare case. If the car were mine...I'd either look at rebuilding my transmission (6" shaft) and keeping the stock driveshaft, or putting in my buddy's transmission and getting my driveshaft cut down.

Rebuilding the tranny sounds like a better idea to me...as the 350 trannys require some special tools that should be readily available at the local parts store but the actual rebuilding should be fairly straightforward to accomplish over a weekend.
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Old 05-02-2009, 01:49 PM
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Jakeshoe has a nice TH350 build article at the top of the trans section here. The 350 doesn't take many specialty tools. Maybe just this one.>>>>>>>>>>
https://www.700r4l60e.com/store/prod...&cat=63&page=1
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Old 05-04-2009, 12:24 AM
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hinklejd

Thanks for the suggestion. the CURRENT tranny in the car was the stock olds. 403 bolt pattern tranny. Being that I installed a small block cheby that cranks out nearly 500 horses + a NOS bottle with 4.10 rear gears, I may have been pressing my luck by using an adapter plate sandwiched between motor and bell housing.

I was keen on using a Chevy bolt 350 Tranny that has the proper bolt patters for my block eliminating the need for an adapter plate. I wanted to avoid CUTTING or modifying the drive shaft in any way shape or form. So the only problem I was having was by using my buddy's chevy bolt pattern tranny Im at the mercy of modifying the drive shaft.

Since BOTH tranny's are out side by side on the bench. I'll strip them both down. I have planned on using my ORIGINAL tail shaft so NO drive shaft mod will be necessary. While BOTH tranny's are on the bench, as you mentioned, for a fairly low cost a rebuild may be the best way to go. I have NEVER rebuilt a 350 but fortunately its WHO you know in this world. A gentlemen I know can build them in his sleep. His fee a case of beer (lets just hope he drinks it AFTER its built )

So if im "NOT" missing anything here? By using my original tail shaft the original output shaft has to go with it. Meaning the entire thing has to come apart from front to back. Im pretty eager to watch and learn the process. Haven't dipped my feet in the 350 waters yet.

Thanks again everyone
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Old 05-04-2009, 11:48 AM
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You've pretty much got it. Tear them both down, then pull the output shaft and tailshaft housing from both and swap. A performance rebuild would also be good for the power you're putting out.


Use compressed air for cleaning -- no rags. Lint from rags will get caught in the passages and kill the trans.
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Old 05-04-2009, 11:55 AM
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Quote:
Originally Posted by sugar ray
Being that I installed a small block cheby that cranks out nearly 500 horses + a NOS bottle with 4.10 rear gears, I may have been pressing my luck by using an adapter plate sandwiched between motor and bell housing.
FWIW, I used TCI adaptor plate between a 455 Pontiac and a Chevy-pattern TH400. The engine was stout, w/a LOT of torque, in a 3500 lb. car.

Never had a minute's problem with the set-up.
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