dmwracing42

iTrader: (3)

So swapped a turbo 400 in that came out of a truck (has the bolt on yoke). I was about to order a driveshaft from Denny's that has the special slip yoke with the counterbore that corrects for the difference in the output shaft on the truck 400s.

My brother works for a part place in CT, and he talked to his "driveshaft guy" who has been "making drive shafts for xxx number of years", and he says a remote slip joint in the driveshaft and retaining the bolt in yoke is the better way to go. He also says the counterbore yoke "doesn't work", which kind of ruins his credibility for me because I've read about plenty of people using it.

I personally think its a stupid idea, but I was curious what you guys had to say about it. My dad seems to be on board with the other idea too, and I can't understand why. Can anyone tell me some kind of advantage to this?

jmd

iTrader: (4)

The third gen driveline is relatively short, so there's no reason to consider going to an alternate style or multi-piece driveline. Also, the suspension travel isn't a huge amount, so the standard short passenger car TH400 yoke length in the conversion yoke is absolutely fine.

With regard to doing a slip joint elsewhere in the driveline, the further away from the ends a joint is placed, the more likely it is to develop a wobble.

Any added diameter to the driveshaft has the torque arm to stay clear of.

And a remote slip is going to make for a slightly heavier driveline than a one-piece tube + two yokes.

Trucks are a little better off with the remote slip because with taller tires, lower driveline rpm is achieved and critical speeds aren't going to happen with tire heights (that would never tend to be run on a third-gen.) They need a longer amount of slip motion because of a greater amount of suspension travel.

On a third gen with ~26" tires and 3.73 gears, you should try and keep the driveline light and simple.

In short, yeah it works in millions of trucks just fine. But in the case of the third-gen, there's zero benefit, and added complexity in what he's suggesting. Denny's will take good care of you.

dmwracing42

iTrader: (3)

Thanks jmd, that's what I figured. I emailed Denny's my concerns, and they were very helpful. Basically, they said either would work, but for any kind of performance, the slip yoke is the way to go.

So thank you, I'm going with Denny's. Anyone else in a similar position, I would recommend them.

AlkyIROC

You don't need a 2 piece driveshaft under a third gen. Just buy a TH400 slip yoke and get a driveshaft made for the proper length once you know where the yoke will be in the transmission.

It doesn't hurt to upgrade everything to 1350 u-joints now. Tranny and diff yokes then when you get a new driveshaft, get 1350 weld ends installed.

jwfirebird

iTrader: (2)

when they did mine they machined the output shaft in the trans. you can just modify the yoke?

dmwracing42

iTrader: (3)

Yeah. The quote from Denny's is that "Denny designed this yoke 25 years ago and it's been used successfully and without complaint by thousands..." yada yada.

Obviousily the supplier is going to tell you that, but some research on other forums (Chevelle and a general hot rodding one) seems to confirm what Denny's told me. It stands to reason that if you can modify the output shaft, the same can be said for the yoke.

jwfirebird

iTrader: (2)

they were taking my trans apart to rebuild it anyway so doesnt much matter, i was just curious because i havent heard of doing it that way before

8Mike9

Replied to wrong thread.