SOLVED: 1988 Super Cab BW1350 manual shift/manual hubs, Extreme vibrations when hubs are locked in...

[GingerKing13]

1988 Super Cab FM146 BW1350 manual shift/manual hubs, Extreme vibrations when hubs are locked in 2WD and 4WD... It feels Fine when hubs are not locked in 2WD!

This started during a day of wheeling at the end of the day. Suddenly I had a very noticeable vibration from the t-case shifter and the gear shifter, enough that it shakes the truck... I have done under it and everything looks intact but there is some 'slop' or play on the T-case end of the front drive shaft. The fluid is fresh and full (changed about 8,000 miles ago). I have never replaced the U-joints and I have had the truck for 6 years. Could this just be a U-joint that's bound up?

Thanks for the help!

 

[SenorNoob]

So when you say with hubs not locked in, did you have the transfer case in 4wd but hubs unlocked?

 

[GingerKing13]

So when you say with hubs not locked in, did you have the transfer case in 4wd but hubs unlocked?

Hubs not locked in 2WD there is not vibration or noise and drives great. Hubs locked and in 2WD or 4WD hard vibration and speed up with increasing vehicle speed.

 

[SenorNoob]

I understand now.
It does sound like a sticky u-joint. Any chance you have greaseable ones? If so that's be first thing I would try.
Kinda odd for one to suddenly stick though unless something was extended/compressed beyond it's usual travel...

 

[GingerKing13]

I understand now.
It does sound like a sticky u-joint. Any chance you have greaseable ones? If so that's be first thing I would try.
Kinda odd for one to suddenly stick though unless something was extended/compressed beyond it's usual travel...

They are non-greasble but Havent been replaced in 6 years. It started doing it shortly after a pretty gnarly rutted trail I was not expecting and have never flexed it that hard.

 

[GingerKing13]

SOLVED!

Thank you for the input SenorNoob, It was a U-Joint on the front driveshaft.