Keep losing my driveshaft

[Soxfan05]

I'll try and explin this the best tht I can.I have a 90 Jimmy with a 350 and a 4 inch lift.Acouple of months ago I had my transfercase rebuilt.To save a couple of bucks my cousin and I decided to take the tcase out ourselves and bring it to the shop to get rebuilt.After I got it back we put it back in.A couple of weeks later I was driving home I heard a big bang and I quit moving.I lost my driveshaft.I found the driveshaft and the yolk.The yolk was broken.I bought a new yolk and had my driveshaft rebalanced and put it back on with new u-joints.A couple of weeks later I was driving home again and I heard a bang and again quit moving.My driveshaft fell off again.This time I didn't find the yolk though.So I bought another new yolk.I don't want to put it back together though because I think I'm doing something wrong.Either I'm doing something wrong when I put the U-Joints on or I did something wrong when I put the transfercase back in.Both times I lost the driveshaft the straps were still on the rear axle along with the u-joint so I'm thinking the problem is with the front u-joint that connects the yolk to the driveshaft.Any suggestions?

[Yukon Jack]

This is the rear driveshaft that you're having problems with?

Very odd, sure sounds like the driveshaft is getting into a sever bind causing the failure. Little surprised this would be happening with a 4" lift.

When the driveshaft was in place, did it appear to be over-extended? Really wouldn't think that would cause the failures your having, but worth knowing that fact.


I'd suggest repair/reinstall the driveshaft assuming lenght is proper then cycle your suspension so you can see if the driveshaft is binding for some reason as the suspension is compressed and fully extended.

Hopefully someone else with more expierence with the late model stuff will chime in.

[Mudder]

Does that yoke just slip into the TC?

[Soxfan05]

It is the rear driveshaft that keeps falling off.I drove the truck for about a year without having any problems.I didn't start having the problems until i put the transfer case back in.That's what's amking me think I did something wrong.And yes the yolk just slips into the transfer case.The yolk is attatched to the driveshaft with a u-joint.

[Mudder]

I bet withthe added lift the yoke is not going into the TC case far enough and when your rear axle drops down from going though a dip it is pulling the yoke out of the TC. Raise the rear of the truck up using the frame or bumper to lift it and see what happens. Let the axel drop down as you raise the truck.

[padresag]

Originally Posted by Mudder

I bet withthe added lift the yoke is not going into the TC case far enough and when your rear axle drops down from going though a dip it is pulling the yoke out of the TC. Raise the rear of the truck up using the frame or bumper to lift it and see what happens. Let the axel drop down as you raise the truck.

that sounds logical
ron

[special-K]

Did you do the lift and the transfer case at the same time?I mean,did you drive it with the lift before the t-case was removed?If so,how much?
It sounds like the driveshaft needs lengthened.Put it all together and take notice of or mark the yoke at the point that enters the t-case.Disconnect the u-joint and see how far the yoke slides in.Ideally,you`d want to be about the middle of the splines when sitting level.
What year is your Blazer and what transfer case do you have?Therew are slip-yioke eliminator kits made for shorter wheelbase 4wds.You end up with a fixed flange out of the t-case,u-joint,then yoke facing the rear,and a splined end of the shaft to slide into the yoke.

[Soxfan05]

Originally Posted by special-K

Did you do the lift and the transfer case at the same time?I mean,did you drive it with the lift before the t-case was removed?If so,how much?
It sounds like the driveshaft needs lengthened.Put it all together and take notice of or mark the yoke at the point that enters the t-case.Disconnect the u-joint and see how far the yoke slides in.Ideally,you`d want to be about the middle of the splines when sitting level.
What year is your Blazer and what transfer case do you have?Therew are slip-yioke eliminator kits made for shorter wheelbase 4wds.You end up with a fixed flange out of the t-case,u-joint,then yoke facing the rear,and a splined end of the shaft to slide into the yoke.

The lift was on the truck when I bought it.I used it as a daily driver for about 5 or 6 months before I had the transfer case rebuilt.The truck in question is a 90 Jimmy fullsize with an NP241C transfer case.I'll try and do what you suggested on Tuesday.That's my next day off of work.Thanks for the help.