Hey guys,

Need help diagnosing an issue I'm having with my truck. The truck starts up fine and mostly runs fine. It accelerates through all the gears smoothly. However, if I just give the truck a little gas - there is often a steady lurching vibration. If I put the gas all the way down, it smoothes out and I can keep accelerating into the next gear. It will do this no matter what gear I am in.

I've changed the clutch - so I don't think thats the issue.
I recently put in a new engine...but it was having this issue with the old engine as well...so I don't think thats the problem

I am guessing it's somewhere else in the drivetrain - transmission / transfer case? I have noticed a little oil around where the rear driveshaft comes out of the transfer case. Maybe a bad bearing there?

Thanks!

 

Have you checked all the u-joints?

 

Thank you. I haven't checked my u-joints before. Do I just jack one of the rear wheels up off the ground and try turning the drive shaft? Looking for extra play / movement?

 

either jack it up or block the wheels and put the truck in neutral so there is no tension on the drivetrain. then grab the driveshaft next to a u-joint and the flange/yoke on the opposite side of the joint and try to move it up/down side/side and twist to see if there is any play in the u-joint, repeat for every u-joint. Also give us more information on your truck, so far all we know is it's an 85 and posted on a Toyota forum, but it wouldn't be the first time someone posted in the wrong forum. If you look at the signature line below you will see that I make it very plain what my rig is and it would help if you did too.

 

Agreed, check the ujoints. perhaps unbalanced wheel or wheels

 

Thanks guys.

My truck is a 1985 4Runner 22re 4x4 - solid axle. Has about 180,000 miles on it.

I finally got under the truck. I chocked the wheels and put it in neutral - I moved around the u-joint/shaft towards the differential, and didn't notice any extra play. However, there was some play at the forward u-joint slightly. There was actually slight movement on the flange/cap coming off the transfer case. Not sure if that is normal.

Also, I was able to turn the driveshaft a bit (~30 degrees) without engaging movement at the wheel - looked like there was play in the differential. Is that normal? I expected no movement at all. It also happens when I keep the truck in gear.

 

There will always be some rotation of the driveshaft before the differential actually turns the tires, 30* sounds like a lot though. what you are mostly concerned with when looking for a vibration is movement of the driveline up and down or side to side or similar play in the yokes/flanges. check the t-case output flange nut to make sure it is tight, that may be your problem.
Phasing of the u-joints is also very important as well as driveshaft balance. your description of a "lurching vibration" leaves some room for doubt as to what is going on. you might want to check your differential fluids and see if #1 it is full, #2 is it discolored, and #3 is there any metal in it or on the drain plug magnet.