Lurch forward when auto trans shifts?

Hello everyone, this i guess is my first real post to the forum here.
I have a 1996 tacoma 4x4 with the 3.4L and auto trans, and i just purchased it about a month or two ago.
One problem i have noticed is that when i come to a complete stop and then let off the brake to start going forward again(im assuming when the transmission shifts) there is a lurch. However, this does not happen in between any other gears or any other time i am driving. Could this be as simple as a trans fluid flush or is this an ominous sign of something worse?

thanks in advance for any input guys

 

How bad of a lurch? It's normal to move forward after releasing the brakes, but not a fast "lurching" motion. Could be something going on with the torque converter.

 

What's your idle RPM...?

 

Does it feel like someone bumped into you?

Sounds like the dreaded axle wrap. The bump, or lurch as you described it, are the rear leaf springs releasing when you let off the brakes. Do your rear leafs have a negative arch?

This is very common on 1st gen Tacoma's, especially those equipped with automatic transmissions.

 

Axle wrap...

 

My 2009 kinda does this. Feels like it has a high idle

 

Damn, Axle Wrap never came up in my research on this truck before. How would one go about diagnosing if they have a wrapped axle? or if they are in near danger of such a thing happening?

 

To be clear, your axle isn't wrapped...your axle is (essentially) wrapping up your rear leaf springs. Remedies I've heard of:
1. New leafs;
2. AAL; and,
3. Traction bar.
I opted for the traction bar; I'd recommend new leafs (or if you're out of $, the AAL).

 

try lubing up the shaft especially the yoke part. keep pumping lube till u see the shaft start to move (because there is play). this usually fixes it. or at least minimalizes it

 

What tacobo670 described isn't axle wrap (or the cure therefor). But try it first...lube's cheaper than leafs or traction bar.

 

ive noticed this too in my 00.. Im sorry, but what is axle wrap?

 

Axle wrap looks like this when you stop...


When you let off the brake and/or accelerate, the leafs "spring" back to their proper position...hence, the "clunk", "thump", or "lurch" you're feeling.

EDIT: If you "search" for axle wrap on TW, you should try spelling it "axel wrap"...I've seen it spelled that way too.

 

cool picture, thank you...

 

Nice drawing. Did you create that? A picture is worth a thousand words...

 

bkieth747's picture of the axle and springs tries to depict the battle of forces between the brakes (which are structurally part of your axle housing) and the momentum (forward energy) of your truck. One of the jobs of the springs is to lock down the axle as it tries to rotate when you apply the brakes to dissipate forward energy. The term "wrap" is really trying to describe the rotation of the axle.

The phenomenon of axle wrap is common to auto tranny's but also happens on manuals, though to a lesser degree. Hard braking brings out the worst of this.

The stock Tacoma springs seem to be especially vulnerable to axle wrap.

 

axle wrap seems like a likely culprit now that i think about it. im planning on putting 5100s all around and a small block in the rear, might just do a AAL at the same time and see if that solves the issue.

the springs are not negative arch, but they are pretty damn close... so this very well may be the problem

 

No...I can't take credit for that one...google image search for axle wrap.