I have a M-20 and the question I have is how far should the yoke insert into the trans. Mine inserts about 2 5/8" and then after I pull the yoke back out to get my one inch clearance I only have about 2 inches of spline engagement. Is 2 " spline engagement enough? I ahve a 454 and it has lots of torque and don't want to tear something up if I can help it. HELP!!!!!! :confused:

The output shaft of the transmission should stick out about 3/4" past the housing. Are you saying that even with this 3/4" that you only have 2"? You really only need 3/4" clearance. Push the yolk all the way in then pull it out 3/4" and that's where it should be. Some drive shaft shops will tell you 3/4" some 7/8" some 1". The shaft only travels about 1/8 to 3/16" with stock suspension anyway. The reason you need at least 3/4" is so you can remove and install the drive shaft while the suspension is hanging. Things are kind of tight with less than 3/4" On a first gen car I always go with 3/4" and never have a problem.
Jim

With the 3/4 sticking out past the housing, I have about 2" maybe 2 1/4" of total spline engagement. The is if I pull the shaft back out to allow my clearance of about 1". I can probably get a little more if I only allow about 3/4 clearance. This will give me about 2 1/2" spline engagement. Is this enough?

If you bottom out the slip yolk, the part of the splined output shaft that sticks out of the tranny 3/4" will actually go past the machined seal area of the yolk on the inside. Push the yolk in all the way then pull it out 3/4" and make a mark on the yolk at the seal. Pull the yolk out and measure from the end of the yolk to the mark and add the 3/4" that sticks out and you will find you have 3-3/8" to 3-1/2" of spline contact. This is plenty. The two yolks I have here measure 3-3/8 and 3-1/2" long on the seal surface area. If your yolk is shorter (it may have been cut) I would get another yolk.
Jim

GMJim,
Thanks so much for your help, but the problem I am having is I can only get a new slip yoke to inset about 2 3/4 inches and is seems to bind on something. If I try to push it a little hard is binds and is hard to pull back out. I guess the real question is why is my new yoke (I have tried several also) only going in about 2 3/4 inches. If I pull the yoke back out about 3/4 " this wilol onlw five me about 2" of spline engagment. This enough? Someone told me taht theoutput shaft could be slightly twisted. Not sure what to do about this is this actually the case. I guesss replace the output shaft if I can find one.

The binding is a new addition to this equasion. The output shaft being bent is a definate possibility. Driving this car this way with the potential big block torque you have makes it a time bomb. The type of steel this is made of will only bend so far then it will break. Or worse, the yolk could split as a result of the splines creating a uneven load and it will take out the tail housing. if you're driving fast enough it could cause bigger problems. I think it's time you visited a tranny shop for an evaluation of what's wrong.
Jim

GMJim,,
Thanks so much for your help!!!! The trammy shop cleaned some burs off of my spline and said a new yoke would slide right up on it now to allow full spline engagement. Thank goodness the output shaft wasn't twisted and feared. Ordered a new drive shaft and will pick it up today about lunch and can't wait to try it out. The trans shop also cleaned the shifter and adjusted the linkage and it shifts much better, os far at least. Only time will tell. They didn't charge me too much so I can't complain. Thanks again!!!

GMJim,,
Thanks so much for your help!!!! The tranny shop cleaned some burs off of my spline and said a new yoke would slide right up on it now to allow full spline engagement. Thank goodness the output shaft wasn't twisted and feared. Ordered a new drive shaft and will pick it up today about lunch and can't wait to try it out. The trans shop also cleaned the shifter and adjusted the linkage and it shifts much better, so far at least. Only time will tell. They didn't charge me too much so I can't complain. Thanks again!!!

I'm glad things turned out ok! Sometimes it's best to get professional advise in person, where they can look at the problem. Good luck with the drive shaft. Happy motoring!
Jim

Got the drivve shaft back this morning and put it in. What a diffence a custom drive shaft makes "VS' a standard drive shaft. I thought my car rode OK before but now with the new drive shaft it rides 100 smoother. The old drive shaft must had been out of balance or something.