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Old 11-14-2009, 07:17 PM   #1
jackyl9999
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Turbo 350 Tailshaft question

Hey everybody. I have purchased a engine/trans combo from a co-worker. 350-350trans. He had it in a 86 model 2wd/Swb. I went to hook up my drive shaft tonight and it is too long. What is the difference length wise in turbo 350 transmission tailshafts?
How long is the tailshaft in a 70 model for a 2wd?



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Old 11-14-2009, 07:29 PM   #2
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Re: Turbo 350 Tailshaft question

There are 3 different lengths of TH350s. The 6 inch, 9 inch, and 12 inch (very uncommon to find).

Your early truck would have had a 6 inch unit. The later model would have had the 9 inch (same length as a 700R4, not coincidentally). I swapped many, many burnt up 700R4s for straight 9 inch TH350s and my money says someone has done exactly that to your 86 model donor. The OD fails and people go to the TH350 for reliability and lower repair cost.

Last edited by Tx Firefighter; 11-14-2009 at 07:30 PM.
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Old 11-14-2009, 07:31 PM   #3
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Re: Turbo 350 Tailshaft question

According to tci transmissions they had a 6 and 9 and a 12 inch tail shaft. I believe the 70s were the short shaft 6 inch.
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Old 11-14-2009, 07:35 PM   #4
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Re: Turbo 350 Tailshaft question

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Originally Posted by Tx Firefighter View Post
There are 3 different lengths of TH350s. The 6 inch, 9 inch, and 12 inch (very uncommon to find).

Your early truck would have had a 6 inch unit. The later model would have had the 9 inch (same length as a 700R4, not coincidentally). I swapped many, many burnt up 700R4s for straight 9 inch TH350s and my money says someone has done exactly that to your 86 model donor. The OD fails and people go to the TH350 for reliability and lower repair cost.
Kevin i agree with your answer just a little slow typing.
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Old 11-14-2009, 08:08 PM   #5
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Re: Turbo 350 Tailshaft question

So cut the driveshaft down 3 inches and should be good to go?
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Old 11-14-2009, 08:58 PM   #6
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Re: Turbo 350 Tailshaft question

I am not sure this would work, but perhaps you could remove the 9" tailshaft, cut down the trans output shaft and then install the 6" tailshaft. I am no trans guru, so don't start hacking off that output shaft without someone who knows tells you it can be done. I saw this done once, but it was to install a transfer case and I can't remember what length tailshaft length it was that was cutdown for the switch.
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Old 11-15-2009, 09:17 AM   #7
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Re: Turbo 350 Tailshaft question

I am hoping to get around working on the trans at all. So would cutting the drive shaft down be my easiest option? Any problems to look for?



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Old 11-15-2009, 09:25 AM   #8
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Re: Turbo 350 Tailshaft question

Shortening the shaft would be the easiest fix. If the trans is a known good working unit that is. Most any machine shop could shorten your ds for you and shouldn't cost much at all. It's been quite a few years since I last had one done but it was less than $50. Balancing is another matter. Perhaps there is a driveline shop somewhere near you?
Then there is the option of searching the salvage yards for a ds the right length.
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Old 11-15-2009, 09:26 AM   #9
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Re: Turbo 350 Tailshaft question

If your truck is a short bed and you have your engine mounted in the front set of frame holes, you can get a driveshaft from a later model shortbed truck like the 86 donor or similar. The length will be right and all you have to do is run a conversion u joint on the rear of the driveshaft since you have a 12 bolt and the later trucks used a 10 bolt. I've done this with driveshafts out of donors up through the early 90s. It's quicker and cheaper than shortening your existing shaft.
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Old 11-15-2009, 09:44 AM   #10
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Re: Turbo 350 Tailshaft question

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Originally Posted by westofb View Post
I am not sure this would work, but perhaps you could remove the 9" tailshaft, cut down the trans output shaft and then install the 6" tailshaft. I am no trans guru, so don't start hacking off that output shaft without someone who knows tells you it can be done. I saw this done once, but it was to install a transfer case and I can't remember what length tailshaft length it was that was cutdown for the switch.

I don't think that will work but I have in the past pulled turbo 350's apart and swapped in different tail shafts. We have done this to convert a two wheel drive trans to four wheel drive by changing the tail shafts. By the time you buy a gasket set and spend the time doing it the expense and time would be more than having the driveshaft shortened or swapping drive shafts though.

As for myself I'd try to swap driveshafts and stash the original one in the shed in case the long shaft trans ever gave out. That might be a headache eliminator somewhere down the road if you have to swap back to a short shaft trans.

Last edited by mr48chev; 11-15-2009 at 09:45 AM.
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Old 11-15-2009, 04:05 PM   #11
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Re: Turbo 350 Tailshaft question

cut your shaft or go to the junk yard and find on. look at S-10's I used one
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Old 11-15-2009, 06:32 PM   #12
jackyl9999
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Re: Turbo 350 Tailshaft question

I think I am going to get a local shop to cut down my shaft 3 inches. If I ever happen to put a new transmission in the truck, I plan on going with a 700r4 that I have in storage. Thanks for all the input guys.


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