torque converter going? 4T60E

[Shadow24v]

ok, new on the forums here, but been a DIY wrench-head for a few years. i have a 1996 3.1L chevy Lumina with 214,xxx miles on it. engine seems to be running fine, needs a tuneup and a T-stat (stays pegged cold all the time), but i have some questions about the 4T60E...

my questions are:

1) when in 4th gear and i tip in a bit for a little more speed or going up a hill, occasionally ill get a growl out of what i think is the transmission (never occurs during idle/stop or neutral free-rev, only under load, and 98% of the time in 4th gear) if i let out for a split second and get back in, it usually goes away. is this possibly an issue with the torque converter?

2) when i step on it to get up to highway speed or pass someone, the shifts seem a little slow and jerky, this just normal wear and tear?

would a bit of lucas help this situation out? id prefer it not die on me til i get home for summer and possibly rebuild the tranny

Thanks in advance

p.s. rebuilt is out of the question ATM, im 400 miles away from home and tools at college

[91parkave]

Check you vacum modulator first, there shoulld be a vacum line running to the tranny, should be a 10mm IIRC bolt hholding a clamp holding the unit in, tkae it out and press on the end of the modulator. If its very hard to compress, that might be your problem, plus there only 12 bucks at autozone and adjustable. hope this

[Shadow24v]

i havent worked on this car much as its usually taken to our mechanics (i only have the use of it until my project car is done) so where on the trans is the modulator?

[Azrael]

It'll be on the front of the transmission on the driver side. It'll have a vacuum line going up to the side of the intake manifold near the throttlebody.

[Shadow24v]

ok thanks.

any idea on the growling though? ive heard that the converters let go on these cars sometimes....

our mechanic (Factory GM trained, die-hard GM guy) advised me not to do a fluid/filter change on the tranny as we have no idea when it was done last (probably pre-100K) and that it could grenade the tranny. *shrug*

[gpse3400]

The converters are actully the good part of the transmission.. The modulator might actually fix the problems you are having.... I'd change the fluid. Brown fluid is not something you want. If the unit is going to fail it's going to fail.

[91parkave]

if its a high mileage car then just drop the pan and fill with new fluid, filter, dont bother with the "trans flush". anyway heres a pic hope this helps

[Shadow24v]

thanks, that gives me a good idea as to what/where it is.

as for the tranny fluid, i pulled the dipstick a couple months ago and it smells a bit burnt....possibly cause the fade in grip after the shift? i also read somewhere that pulling the pan only gets about 1/2 the fluid out of the tranny.

btw, that a buick 3.8 or somesuch? i dont recognise the UIM on it, not like the one on my 3.1 *shrug*

[91parkave]

yup 3.8 sorry i know we have diffrent cars and all but same trans, yes i know droping the pan only gets 1/2 out but if you do it frequently enough it wont be a problem, and hey its better than taking the risk of "flushing it out" and risk not being able to drive home....

[Shadow24v]

thats true enough. probably should do the filter as well id think. any idea what the half-volume drained would be? i heard something like 6 qts

on another note, the SES light has tripped a couple times with a P1870 - manufacturer control transmission code

[91parkave]

IIRC its a ghost code for something else, what exactly im not sure of, the times i have seen it it turned it out to be a loose ground connection, buth that was on a 4t65 though

[nixtux]

you could always drop the pan and undo the cooler lines and flush just the cooler. Then refill /w new filter and fluid. I think I used a 17mm wrench to get the cooler lines off.

About 1,500mi before it went out I noticed shudders during shifts. Not all the time though. I don't recall any distinct sounds but I think I noticed a sound the last time I drove it (right before it went out,) kind of a clunky like noise coming from the transmission area. I also have a value tap and it kind made it difficult to determine the location.

I think my TC went out from being over torqued to my flex plate. I had noticed shaky shifts and around a mile before my transmission died I noticed a shudder at idle. I had kind of noticed it for about a week but didn't think much of it. But it got progressively worse. Then nothing. I had to coast a 1/4 mile home in neutral. Got in my drive way and drive didn't work. But 1st did. Pulled it in. The next time I started it was to move it in my garage and no gear worked.

Like you, I had burnt fluid and I choose not to change it after I noticed it. After I bought the car I was told it was flushed and 25k later I checked it and it was something terrible. Maybe it caused it to go out. I don't know, but I choose not to change it for the fact that flushing it probably would have killed it quicker. Though it would've been warmer so that would have been desirable.

In the end I had a bad transmission and a chewed flex plate.

[Shadow24v]

i see what you mean. AFAIK, we haven't had anything done with the tranny since we've owned the car (about 7 years or so) about 12-18 months ago the water pump died, and im wondering if that might have cooked the tranny fluid.

aside from less sharp shifts the only thing that bothers me is the growl from the trans occasionally. other than the tune-up an assorted other things i should do, she seems to be doing ok *shrug* i just hope its not the TC beginning to go

[91parkave]

you could always drop the pan and undo the cooler lines and flush just the cooler. Then refill /w new filter and fluid. I think I used a 17mm wrench to get the cooler lines off.

About 1,500mi before it went out I noticed shudders during shifts. Not all the time though. I don't recall any distinct sounds but I think I noticed a sound the last time I drove it (right before it went out,) kind of a clunky like noise coming from the transmission area. I also have a value tap and it kind made it difficult to determine the location.

I think my TC went out from being over torqued to my flex plate. I had noticed shaky shifts and around a mile before my transmission died I noticed a shudder at idle. I had kind of noticed it for about a week but didn't think much of it. But it got progressively worse. Then nothing. I had to coast a 1/4 mile home in neutral. Got in my drive way and drive didn't work. But 1st did. Pulled it in. The next time I started it was to move it in my garage and no gear worked.

Like you, I had burnt fluid and I choose not to change it after I noticed it. After I bought the car I was told it was flushed and 25k later I checked it and it was something terrible. Maybe it caused it to go out. I don't know, but I choose not to change it for the fact that flushing it probably would have killed it quicker. Though it would've been warmer so that would have been desirable.

In the end I had a bad transmission and a chewed flex plate.

over tourqed TC wont cause that whoever installed the TC didnt properly set the TC on the input shaft causing your problem

[sharkey]

code p1870 is torque converter clutch slippage detected. the computer is picking up a slipping converter, however this code can be deceiving as it bases this off the engine rpm, output speed sensor rpm and calculates what rpm it should be based on what gear you are in (3rd or 4th). this code can actualy be caused by a slipping clutch inside the tranny aswell as a slipping converter. now dont just go out and replace the converter, it could be caused by a worn out valve body.

this code is more commonly seen on 4l60e's and the fix for it is to block the pwm valve over so lockup is either on or off, no modulated lockup.