mrdiehl

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!

NYHumpinUtah

iTrader: (1)

Have you checked all the u-joints?

mrdiehl

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?

akwheeler

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.

leiferikson

Agreed, check the ujoints. perhaps unbalanced wheel or wheels

mrdiehl

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.

akwheeler

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.