My 91 E150 (351, E4OD, 70k) has what I can only describe as a "clunk" in 1st gear when accelerating from a stop light at anywhere between 1/2 and full throttle. I checked the rear end for signs of wear on the ring and pinion and the u-joints. They appear to be Ok. I've also checked the engine and trans mounts (It kind of feels like what would happen if you had a bad engine mount and the engine was moving under load) and they look good. Which leads me to the tranny. I took the thing to AAMCO for an inspection and they said it looks good to them and drives well. I think they missed something.

Has anyone else had this problem or have any thoughts on what this might be?

Thanks

 

Personally, I have a C6 and was experiencing the same thing.
It went away, don't know why.(I think it's the drum brakes.)

A mechanic suggested that there may be a broken accumulator spring.
Made sense, since the accumulator pistons in the trans take the
hydraulic "shock" to keep operation smooth.

This might not help, but just a thought.

Were the ring gear bolts tight?

Are you're rear brakes sticking, then releasing when pulling away?

Parking brake cables?

 

get underneath and grab the driveshaft, leave the tranny in park, then turn the driveshaft there should be very little play in it. It sounds like a yoke is going, or a ujoint...

 

I tried the driveshaft check, things are very tight with little to no play.

I'm not sure if the rear brakes are sticking, what is the best way to tell? I just replaced shoes and hardware last August...

How do I check the accumulator spring? Do I need to drop the valve body in the trans?

 

Don't mess with the accumulator spring, that's not the problem. Most likely you have a bad motor or transmission mount. Remove the engine cover and try holding the brake pedal and giving it however much throttle is required to make the clunk. Watch the motor and see how much it moves. I bet that is where you will find your clunk. If not the engine mounts, the rear transmission mount might be hitting the cross member.

Another possibility is a bad rear spring isolator. Under heavy acceleration the spring eye can cause a clunk. The u-jounts are still a possibility too. There is no way you can put enough pressure on the driveshaft with your hands to duplicate the load from acceleration.

I really doubt its the transmission. I would bet the guys at the AAMCO Center that checked it would have caught anything in the tranny.

Steve
Owner: AAMCO Center #7080

 

hey rustbucket, have you found the problem? i was just checking out old posts and i also have this problem on my '99e150. i was wondering if you found and/or fixed the clunk.

 

When you check the driveline for play, don't leave tranny in park. It cause your drive line to bind so you won't beable to feel any play.

Chock your wheels and put in neutral.

 

I still haven't found the problem, but the good news is that it hasn't gotten any worse. Kaleo, I'll try your method for checking the u-joints, but I really don't think that is the culprit. I also need to check the spring eye bushings and stuff.

I'll let you know what surfaces.

 

Perhaps your rear brakes are not sticking but the adjusters are full of dust and won't let the shoes back out any. Just drop them out from between the shoes and clean them up good to be sure they will back out when the shoes decompress. See if things feel better after that.

 

Hey just saw your post, I have a '94 E-250 with overdrive and it started to act up and shift irregularly and clunk. The Trans has a lock up converter and when the fluid gets old it starts to shift badly. I changed the fluid and filter and dissconected the battery for twenty minutes and it was a total success!! If the drive line is good and you have not had the fluid changed, I urge you to do so. I bet you will find that the clunk will be gone.

 

Hey kevin-11 here, was wondering if you found the problem yet? I hope you did, if so let us know so we can learn something. Thanks- kevin-11