Any thoughts on this? only happens when car is warmed up. I'll sit at a light and drop from OD to 1st so I can shift up manually. Car bucks for a split second then idles normally again. What is happening in there? I've never heard of a car jerking when going from drive to 1st. neutral to drive, sure. but never this. Any ideas?

 

Assuming all drive-line components are tight, and that your motor mounts and transmission mounts are solid, and assuming that your gas mileage is normal, and that your automatic shift-points occur when they should, and assuming that your fluid levels are correct (and are the correct fluid), the diagnosis is likely that you have a 700r4 bolted to your motor.

 

Well spoken, doctor W.E.G.

 

When you say "clunks", do you mean the car lurches forward?

 

W.E.G, . lol. but everything on there is good as far as I know. I guess I should try and explain this a little better haha.The RPMs drop and the car lurches forward slightly when I put it from OD to 1st. Best I can describe it is that it feels like I'm putting it in drive from park or neutral... but it's already in drive.

 

So many thirdgen's suffer from vacuum leaks, that I find it hard to even discuss performance issues until I know that all vacuum leaks are eliminated.

For instance, consider this:
ECM perceives load on engine when automatic trans is in gear.
ECM adjusts idle mixture based on presence of load.
Driver shifts trans out of gear (even for a second)
ECM perceives change in load
ECM adjusts (leans) mixture based on change in load, and also accounting for vacuum leak(s)
Isn't the result a bit like revving your engine between gear changes, rather than letting off as would normally be desired?

Throw in sensors not feeding correct (or any) info, and the relationship between the ECM and the information it has to work with, it becomes quite like discussing your three-team bowling schedule with a disinterested person who suffers from ADD. Not a perfect metaphor, I will grant, but the result is nonetheless predictably unsatisfactory, and quite frustrating.

If you are wondering what in the world am I babbling about, I'm guessing vacuum leak as at least a contributor to your issue.

...assuming you don't have bad motor mounts, or some such

 

Manual 1st engages the lo/rev clutch pack. That shift position and the R shift position are the only times that clutch pack is engaged.

Also, in manual 2nd or 1st the line pressure is increased. By quite a bit.

RBob.

 

What RBob says is correct. That being said, your transmission's behavior is not normal. I suspect that your trans may have an internal oil leak, or simply worn out frictions, causing the forward clutch not to engage firmly at idle. Therefore you notice a bump when the low reverse clutch is engaged in manual low.

Or even more likely, the pump is worn and not producing sufficient line rise in D4 at idle. That is why you feel a difference when you engage manual 1st and the auxiliary boost valve is activated. On a healthy 700R4, you cannot feel any change shifting through the forward gears at idle with the brake applied.

The 700R4 is fully hydraulic. Aside from TCC control, there is no input from the ECM to the transmission. The TV cable provides throttle position input to the unit.