Truck tries to shake itself to death. What's wrong?

[Lee in Texas]

I just got my '86 Ranger back from a shop that stretched the frame. It's a supercab that had its frame cut and the back of a longbed frame grafted on. It is now undriveable. Starting at around 12-15mph, it feels like I'm driving on a washboard gravel road, and gets worse as speed increases. I'm guessing it's either an unbalanced driveshaft (it was lengthened 6 inches or so) or improper pinion angle. Possibly a combination of the two. I'm new to this, so I hope someone out there knows more about this than me.

It will not be going back to the same guy for a warranty repair. He had my truck for 11 months. I'm not going through that again.

 

[alwaysFlOoReD]

Sounds like you have the same ideas I would. Tho you can check to make sure that the u-joints are in phase.
With a single u-joint at each end of the shaft, the trans and pinion center-lines should be parallel.
Good luck,

Richard

 

[70roadrunner]

definitely sounds like a driveshaft issue. my guess would be that the driveshaft is bent if it causes the truck to shake. I would take the truck to a reputable driveshaft shop to get it corrected. have them inspect the mods to make sure its safe while u have it there!

 

[adsm08]

Do you have the bed on yet? If not the weight of the bed may be enough to bring any incorrect drive line angles back into the proper operating range.

 

[Lee in Texas]

The bed is on.

 

[ab_slack]

Yes balance, trans and pinion lines in parallel. Both those directly related to the work done. As mentioned too the shaft phasing too and possibly u-joints would cause same sort of problem

Might also want to make sure the slip yoke (is that the correct term) in the drive shaft isn't hitting one limit or another.

 

[alwaysFlOoReD]

This may help diagnose a bad driveshaft or improper work;
http://www.therangerstation.com/forums/attachment.php?attachmentid=12939&d=1389987591