TH400 Driveshaft Question

[85 c-10]

Is that slider on the trans end, or the diff end?

Josh

[slug]

its on the tranny end, the "slip" is between the pink lines.

[85 c-10]

Okay let me think out loud and please let me know if Im on the right track. GM used slip yokes in cars, and the occasional short vehicles with 1pc. D/S TH400's. GM used bolt on yokes for any vehicle with a split D/S. On a short tail 400, are the slip yoke and bolt on yoke the same length? My main concern right now is, I want to make sure if I use a slip yoke, it will engage the trans enough as to not cause severe wear problems on the bushing or yoke seal. I have to have a shaft made no matter what. The yoke I use will determine is I use a slip shaft or not.

Thanks,
Josh

[MylilBowTie]

You can use a ds like Slug posted but I think it would cost more to make. I could be wrong in my assumption about that.

If I was in your situation. I would get a slip yoke for the th400 then have the ds place make it the correct length with your slip yoke. I don't think there is very much length difference in a slip yoke and a bolt on yoke. I would also have then use non greaseable u-joints. The zerk fitting makes the u-joint weaker and doesn't really affect the life that much. Seeing how everything else is getting built up. Its starting to look like the u-joints are the next weak link.

Mainly need to focus on truck parts, after all you own a truck. So we don't need to get it more complicated with other types of vehicles. I forget the magic number on the one piece driveshaft. But after a certain number it is better to use a two piece. I know that long wheel base trucks are right at the end of that magic number. They also mostly use longer tailshaft version of the transmissions. If not they use the two piece or if its heavier duty than a low gvw 1/2 ton. Short wheel base trucks don't need a two piece driveshaft. Being the length of the driveshaft is okay for a one piece. They mostly use short tail transmissions.

[MylilBowTie]

Maybe there is something different when switching over from a bolt on to a slip for the th400?

Got this from Dennys Drive shaft site.
Slip yoke is specifically designed to be used on a T-400 & 4L80 with the Threaded Output shaft. This design will replace the truck style bolt on yoke with a car style slip yoke and allow for proper slip travel and bushing contact for best performance. A must for any threaded output shaft on T-400 & 4L80 transmissions. We designed this yoke to solve this problem over 25 years ago.

Might call them and find out whats different out it.

[454HO]

There is some interesting reading on the Chevelle forum if you want to go searching there. Here are a couple good threads on this subject.

can a slip on yoke from a th400 be used on a th400 that has a bolt on yoke

Turbo 400 Yoke Confusion

th400 bolt on yoke

On that last thread, pay particular attention to what jakeshoe says.

I got the measurements for my ds last night and will be calling Denny's today to order a Nitrous Ready ds. I will ask about the special slip yoke they have to replace the bolt on yoke.

[85 c-10]

Thanks Greg. Im anxious to see what they say.

JOsh

[454HO]

Okay, here is the skinny. The truck style output shaft on the TH400 and 4L80e has a shoulder up inside the tailhousing that acts as a stop for the bolt on yoke. A normal slip yoke will bottom out on that shoulder. What Denny does is machine (counterbore) the inside of a standard slip yoke so that it will clear that shoulder. He did not tell me the diameter or depth of the counterbore or even if it was a critical dimension. He did say that cutting off the end of the yoke was a bad thing... it makes it too short.

So I placed the order for my shaft. Mine measured 60-5/8" from the trans tail to the face of the pinion bearing (no yoke). I am getting the Nitrous Ready shaft, truck slip yoke and forged pinion yoke for 1350 U-joints. The shaft will be 3-1/2" diameter due to the length. My total cost with shipping (oversized box) is $596.90. That includes the $30 web discount for this week.

Oh yeah, he has about a 3 week backlog right now.

[85 c-10]

Greg that is great information. Well, kinda great. That is what I wanted to know. THe next issue I need to resolve is, I have a car 400 but with the BOP pattern. I may drop that off as well and ask him to use that output shaft. If he will, Im getting a slip yoke and 1pc shaft. If he declines, I will get a slip style shaft. Probelm solved for now. Thanks everyone for your input. This saved me a lot of headache later.

Josh Johnston

[454HO]

No problem... glad I could help.

I need to take the tailhousing off of my trans so I can replace the seal. I will try to get a picture of the output shaft for future reference. And of course when my Dennys nr shaft gets here I will get some pics of it too.

[454HO]

Got my Denny's nitrous ready driveshaft yesterday. As promised, here are the pics.

The Denny's tube is 3-1/2" compared to the stock 2-3/4" that was on my truck. And with 1350 U-joints and a forged pinion yoke, it's massive.







These next pics show the difference between the stock bolt-on yoke and the Denny's custom machined slip yoke.







And I just have to say it.... I got a nice shaft.

[85 c-10]

Oh wow. That is huge. Those 1350's are a lot bigger than the 1310. Maybe I should go withthat too.

Josh