Hi again

Sorry for the double post -- I thought it's better to start separate threads for separate questions.

I have a 1989 F-150 5.0 L with the AOD transmission.

When I accelerate somewhat hardy and then immediately lift off the gas pedal, as the truck coasts I can hear a single clunk right after lifting off the gas pedal. It also feels like there's a slight jerk, like someone pushing me from the back. Best way I can describe it is it almost feels like there is some play between the drive shaft and engine, and as I start coasting the drive shaft "runs into" the engine. I don't know if that description makes sense.

Any ideas on (a) what this might be or (b) next steps to diagnose this?

Thanks in advance!

André

 

u joints, rear end, pinion bearing maybe, axle not tight in the springs, spring eye bushings , shocks loose, loose trans mount, trans extension housing bearing or bushing wear, slip joint(if has) wear, shift off worn front end parts, engine mounts.

Its not going to stop(the list) ,you need to try and check a few things. First. Get on the ground and wiggle the driveshaft. Play? That will tell you a lot right there.

Then you can also try doing some reverse braking + driving straight lines, accel and decel. any clunks? Then move forward, notice how it behaves immediately after. shifting/clearances in things like mounts/suspension will be very noticeable or may partially go away, driveline shouldnt change that much (if it was the source) but possibly could.

Id say its old truck the springs are tired, shocks are tired, and your mounts are tired, things like to torque-move around when you are accel, and that can wear those u joints more in particular. the rear end maybe if you had a lot of wear or your truck had someone reset the lash or whatever and wasnt correct and caussed the trailing edge to wear on the teeth. Ever do a rear fluid change? good time to!

 

The usual cause of this is a failing u-joint. Next I would have a look at the differential/axles, then the engine (mounts), then the transmission, in that order. If the clunk is that noticeable it should be easy to find the culprit.

 

My vote is engine mounts.

 

Super helpful quick answers as always guys! Thank you! I'll try to look at these things this weekend if I get to it, probably starting with the u joints since that seems to be a common culprit.

Thanks again,
André

 

Apologies in advance for this super long post. I'm a novice and I really appreciate all the help I get on here and it's a great opportunity for me to learn. That being said, I really hope no one feels obligated to reply!

I know it's been a while since I last posted to this thread, but I have gotten around to wiggle a couple things under the truck today. I really have no clue how much play in all these components is acceptable, so I'm hoping someone might have a look at the videos attached and tell me what's normal and what's not, so I can start to build a feel for these things myself.

First off, I feel that there is too much play in the differential, between the drive shaft turning and the rear wheels spinning. Whenever I change directions (forward/reverse) I can turn the drive shaft a good couple degrees before the wheels spin. See first attached video. But maybe that's normal? Also, as I'm turning the wheels, the resistance is not even. There is one point where it is much harder to turn than otherwise. I have dragging brakes in the front so maybe it's the same in the back and that's the cause of that issue.


There is also a little play in one of the U-joints, I can wiggle it sideways a couple millimeters. The other two are good. Does this warrant a replacement?


Then, there's a mount for the drive shaft with some rubber bushing. The drive shaft moves up and down a good bit inside of that. This does not seem related to my problem, but should I replace it anyways?


Lastly, the output shaft from the transmission has a little play, just a millimeter or so. I've attached a video for that as well. Is that normal?


Also, unrelated, but I was spinning my front right tire and was getting the following tapping sound:


Took the wheel off to try to investigate. After putting it back on, the sound was gone. Anyone have any clue what that might be? I'm glad it's gone, but since I didn't fix anything and didn't figure out what it was, I'm afraid it could come back at any time.

PS: It took me a while to figure out how to embed YouTube videos on this forum. For anyone else wondering, just wrap the link to the video in \[AME\] ... \[/AME\] (without the backslashes)