Bad jerk if I don't feather the pedal????

I'm trying to troubleshoot a jerking problem. I have a 1999 V6 automatic.

If i push the gas pedal in deep, too quickly, or if I let it off too quickly (from deep in), there is a single violent jerk and then all is good.

It's strength seems to be speed dependent. The faster I am going, the stronger it is.

It is worse on inclines.

If I feather the pedal it is not present.

It is stronger if the trans has to downshift. I notice it most when I am trying to pass someone on the highway.

It feels like something is taking a second or so to lock up. Most of the automatics I have driven have done this to some extent, but it is very exaggerated in this truck.

My thinking is:

driveshaft
transmission
mounts

Maybe some slop in the driveshaft that takes a second to lock up. I've checked and can't find any, but I don't honestly know what I am looking for. I've just been turning it by hand at the various joints to see if there is any noticeable play

If it's the transmission, it seems fine otherwise. There isn't any slipping. I bought the truck 6 months ago and had all the fluids changed. The problem has been becoming more noticeable since then. I just changed the trans fluid last week and discovered it has been over-filled for at least 6 months. I don't know if they are related, but like I said, the trans seems fine other wise.

Maybe trans or motor mounts? How do I check them?

Is there something else I'm not considering?

I appreciate any help.

 

i would say its your trans. double check fluid levels, are remeber to check it while its running. was there and metal shavings when you changed the fluids?

 

I would have someone look at your tranny. Mine was doing that and i was able to feather it, some days were better than others. But in the end it left me stranded on the side of the Hwy. No warning or anything. Got a Jasper remanufactured tranny put in at the cost of 3k

 

For the cost of the tow truck you'll need when you are "testing" breaks the truck you can have new driveshaft u-joints and/or center bearing installed.

 

I would start with the basics first . Grab a pry bar and start checking the motor mounts and transmission mounts , rear springs , hanger bearing mount etc .99% of the time the issue is visible .
If you have the back wheels off the ground , you can check the play in the rear diff .
Is the problem noticeable in 4x4 ? is it noticeable in 4x4 low ?
Have you been under the truck to have a look ?
How long has this been happening ?

 

I didin't see any metal shavings. But the fluid didn't look good either (a little burnt, brownish, murky). I switched to synthetic and have checked the level quite a few times since the switch. But it was overfilled for about 6 months (10k miles) with Dino, before this recent switch. Changing to synthetic and having the right level has made the the trans feel MUCH better overall, but the jerk I'm trying to diagnose seems unaffected by the change.

 

By rear springs, do you mean the leaf springs? If so, I can tell you there are shot and need to be replaced. It's on my list. I know that shot leafs can cause the dreaded 'axle wrap' jerk when coming to a stop or taking off, but could they also cause a jerk at all speeds, with a more pronounced one at higher speeds?

It's not noticeable in 4L as I don't use 4L unless I'm under 10MPH.
The same is really true with 4H. I don't use 4H that much but when I do, I'm usually under 25 mph and even in 2H, the jerk is not very noticeable at that low a speed.

I've looked under the truck quite a bit. I'm just not sure what I'm looking for with this one.

I didn't really notice it until about 2.5 months ago when on a long trip through the hills. I was trying to pass someone and when I hit the gas it happened. Then I noticed it there when I let off the gas too quickly.

 

I found this thread:
http://www.tacomaworld.com/forum/1s...just-bought-02-taco-transmission-concern.html
Seems like it might just be a characteristic of the 1st gen. Tacoma AT.