th400 ? - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

 
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post #1 of 13 (permalink) Old Feb 6th, 08, 8:56 PM Thread Starter
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th400 ?

can a slip on yoke from a th400 be used on a th400 that has a bolt on yoke or do you have to change the output shaft thanks luke
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post #2 of 13 (permalink) Old Feb 6th, 08, 9:52 PM
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Re: th400 ?

I have a standard length slip yoke on my TH400 trans with the bolt on yoke output shaft. I have yet to have a problem with any leaks. Some on here have had problems. Perhaps try doing a Search this thread option for other threads with similar topic.

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post #3 of 13 (permalink) Old Feb 7th, 08, 12:41 AM
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Re: th400 ?

I'm running a slip Yoke on My bolt output shaft. No problemo.

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post #4 of 13 (permalink) Old Feb 7th, 08, 1:21 PM
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Re: th400 ?

Would it make any sense to shorten the length of the yoke in order to bring the u-joint assembly closer to the transmission.
On mine the slip yoke will only slip into the trans about 11/2" due to the way the output shaft is designed. It may not matter but it looks stupid sticking way out like that. I measured the yoke and it looks like if I whack off about inch and a half I will bring the u-joint closer, like you would expect.
I need to get a custom length drive shaft anyway so other than the additional length to the drive shaft that part won't change.
A couple of drive line companies say they have a yoke for this application but won't say what it is exactly. I don't want to buy another yoke if the one I already bought will work.
I know there is a whole gang of these truck trannys out there working just fine but I can't seem to nail this one down.
There are plenty of threads here that I have gone through on the exact same issue. Not one has the answer to my question
I am not asking where to buy parts or how to measure for a drive shaft or who can modify my output shaft or where I can get a different output shaft.
The question is: Do I cut my yoke as described above or do I use it as is. This is a yoke for a 400 it fits the shaft fine. I can't really think of a reason it wouldn't as is. It just looks stupid.

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post #5 of 13 (permalink) Old Feb 7th, 08, 3:10 PM
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Re: th400 ?

Are you hitting the o-ring on the output shaft ?

Last edited by Mike; Feb 7th, 08 at 5:41 PM.
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post #6 of 13 (permalink) Old Feb 7th, 08, 3:40 PM
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Re: th400 ?

If it works as is ,use it.You will not gain anything by cutting it off shorter.But if you want more travel, you can bore the inside of the yoke to 1.375 dia.(might vary on some units) to clear the o-ring boss at the end of the splines on the output shaft.The problem here for some high perf. applications might be the loss of spline contact and strength. Spline length is 3" with the stop at 3.25" so the deeper the bore the less contact the splines have .Driveshaft length for this setup has to be exact.The right way to fix this is to bolt the yoke on as designed and put a slip yoke and stub on the driveshaft but its heavier and more expensive
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post #7 of 13 (permalink) Old Feb 7th, 08, 6:35 PM
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Re: th400 ?

I hadn't realized that the length of the splines were limited. I thought they were the full length of the yoke. I'll double check .
As far as boring out the front of the yoke. I think that would be the equivalent of whacking off a like amount which I could do with a die grinder and a cut off wheel.
I thought about the slip spline on the drive shaft. That would insure no leaks at the tail shaft but probably pretty costly compared to a regular set up.
I guess the overall length is pretty short to consider center bearing 2 piece.
Well at least we covered all the angles (no pun intended).
Not that it matters now, but I don't remember seeing an o ring on the shaft when I pulled the tail extension.

I can't remember if I saved the drive shaft from the pick up that the trans came from. If I had that drive shaft, could those pieces be used to make a slip shaft for the Chevelle?

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Last edited by swcash; Feb 7th, 08 at 6:50 PM. Reason: spelling error
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post #8 of 13 (permalink) Old Feb 7th, 08, 6:49 PM
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Re: th400 ?

Am I hitting the o-ring. I haven't sized the drive shaft as of yet. So no I'm not hitting the o-ring or the tail shaft behind the o-ring.
When I slide the yoke onto the trans tail shaft. It only goes a short distance before it bottoms out. Once you pull it back to allow for drive shaft movement there is not a whole lot of contact between yoke and spline of trans. Not only that It looks odd with the yoke hanging out so far. I.m sure it would work that way and they are probably strong enough to get by with the limited contact area.
Boring the yoke will allow it to enter the trans housing more and it will look more normal, but that wont change the amount of spline to yoke contact. It will be less if the yoke does not have the splines running the full length of the yoke.I feel like I'm getting the shaft from this drive.......line

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post #9 of 13 (permalink) Old Feb 7th, 08, 9:32 PM
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Re: th400 ?

I been through this before.

Do not use a yoke that is sticking way out the end of the tranny. It should only be out around 1 inch.

Do yourself a favor and go to a tranny shop and ask to see a few output shafts from a turbo 400.

Then you will understand the spline and length situation and can make an informed decision.

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post #10 of 13 (permalink) Old Feb 8th, 08, 9:12 AM
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Re: th400 ?

If you have been through this before couldn't you just share the experience we us rather than send me off to a drive line shop.
If the yoke needs to stick out 1 inch then it needs to be shortened. yes, no?
It's impossible to get a straight answer on this issue. Every time I research this I end up right back where I started. Can this issue be put to rest? I doubt it.
OK so I go to the driveling shop and look at tail shafts. And then I will be able to make a decision?
Will their tail shaft look different than my tail shaft and what am I looking for?
No disrespect really. I'm probably having a bad day, and this simple issue is wearing me down. I've searched the boards and found that this EXACT issue comes up over and over again. But it is never resolved. I asked in my first post for help. I thought I made myself clear that I didn't want to be told to go buy the yoke from a driveling company.
Can't you see what we are doing here?
If I were putting an engine together and ask a question about setting the thrust. Would the proper response be to tell me to buy a short block from Pep boys?
I need a nap. I do appreciate everyone help.Maybe I need to start over on this one after all I did hijack the thread and I apologize for that , That was not my intention. I saw the topic, I got excited, and I jumped in. Sorry

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post #11 of 13 (permalink) Old Feb 8th, 08, 2:44 PM
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Re: th400 ?

Here is a link to a post I made May 30, 2005.

It is a few years ago and I don't remember all the details, but I think this thread will help you.

Turbo 400 Yoke Confusion

I can understand a bit of frustration, but there are many frustrating issues when it comes to the old muscle cars and modifications.

The reason I suggested to go to a tranny shop and look at the various output shafts is that a picture is worth a thousand words. I don't have a picture so the next best is to see one for real.

Be patient, we all try and help, sometimes just don't have time at every moment to get into the last detail.

Bottom line is to use the slip yoke that is about 5.5 inches long. It should not bottom out against the end of the tailhousing but bottom at the shoulder of the output shaft. It should not be very far from the end of the tailhousing, I would say a half inch or so. From there pull the yoke about 3/4 - 1 inch, then measure for your driveshaft length.

I have seen guys using really long yokes that stick way out. This creates a greater opportunity for the driveshaft to "whip" and will be harder on the tailshaft bushing.

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post #12 of 13 (permalink) Old Feb 8th, 08, 3:45 PM
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Re: th400 ?

You are way too stressed over this yoke thing .The problem is you are trying to use something against the way it was designed,sort of like the round peg in the square hole thing.Bolt the original yoke in place and go to your local driveshaft guy and explain what you are doing ,with center -to -center diminsion, and he can build a complete new balanced shaft for less than $300,maybe a lot less if your existing driveshaft has good donor parts. This is a lot easier,and cheaper, than pulling the trans and putting in the correct output shaft to match your slip yoke
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post #13 of 13 (permalink) Old Feb 8th, 08, 7:09 PM
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Re: th400 ?

Pull The Tail And Use A Dremel To Grind Down .030" Behind The Oring And It Will Slide Over The Raised Area And All The Way In

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