1994 LT1 4L60E Transmission problem

[TODD L GRIFFITH]

To all of you that have a 4L60E automatic. Something real strange happened to my tranny. Under WOT my tranny would not shift from first to second and I would hit the rev limiter. If I backed off on the throttle, it would shift. This problem drove me nuts. All I needed was a pesky little Mustang to screw with me, and I couldn't respond. First I checked the fluid level, replaced the filter, added new fluid and the problem still existed. I thought the problem must be in the transmission, maybe faulty shift valves, modulator gone, thought it could be a the converter. I started to read the Chilton's, because the Haynes sucks for my car. I figured that the problem could be with the PCM. Upon researching the transmission in the book and online, there really isn't a whole lot of info. I did read that modulator pressure is effected by manifold intake vacuum. Sure as $#!% my MAP sensor was faulty. My MAP sensor was sending the wrong voltage to the PCM under WOT and the tranny modulator couldn't tell the shift valves that they neded to shift at the right time. The problem only existed under wide open throttle. Under normal driving conditions the problem did not exist. I think that this was because the voltage output of the MAP was normally in the voltage range according to the MAP sensor voltage specifications. My max voltage was only 2V between terminals A and B at 29.92" Hg. sea level, key on engine not running, instead of 4V. If this helps anyone I'm happy with that. If anyone has a comment, I would appreciate it. (The car does run alot smoother with the new MAP sensor. It wasn't really noticable until I replaced it. Time to by a scan tool I guess.)

[TODD L GRIFFITH]

I really have enjoyed the corvette action center, and have been emailing a few members for months now and have made some great friends.

[redc4corvette]

also 4l60e has a problem with the pressure regulator solenoid in the trans .
If you put the trans in o-drive at wide open throttle and feel a vibration or a shimmy
its bad if it does it in drive replace it asap or you will be buying a trans.

[TODD L GRIFFITH]

Thanks for responding, but this thread was posted 11/01, so I haven't owned that C4 in a few years. I ended up rebuilding that transmission at about 89k miles. I traded the car 3/02 for a 99' C5 Hardtop and traded that one 7/03 for a new 03' 50th Anniversary ZO6. I plan on keeping the 03' 50th ZO6 forever, but that depends on if I get the C6 ZO6 fever or not. I really would like to own a 70' coupe too, just add to my wish list.

[UB2 SLOW]

WOW! Old thread!!!

[Idaho Slim]

Yes old thread, and oh so very timely!!! since this is exactly what i am experiencing and having a problem with. (See my thread here)..... http://corvetteactioncenter.com/foru...ad.php?t=48761

GRIFF could you take the time and read my thread and see if my symptoms correlate to yours?? As a example, last night, 2 days since getting it back from the dealer with the no change & same problem, I tried punching it again at 35 ish, it was lazy, did not get into "Haul Azz" mode, geez, my bombed Powerstroke would take off faster at this speed! . From a dead stop, if I did not manually put it in low, it was a dog off the line for about 3 secs then really scream. The perfomance is there, I punched it WOTon the highway from 70 and hit 136 in about 8-10 secs but when there (136ish), the transmission would not shift out of drive 5600 rpm, until i slightly let off the pedal, then continued on to 141+ as normal. Sound famaliar?? If so do you think this may be what I need to doo is replace the MAP sensor, and can I doo it or does a Chevrolet dealer need to doo it??

Thanks for your reply!

[TODD L GRIFFITH]

The problem sounds similar enough. The MAP sensor is about $40-$50 and can be ordered from Autozone. Easy to replace, mounted on top of your throttlebody unplug, remove, install plug in that simple. Eventually I had to rebuild the transmission.

[Idaho Slim]

Happy Days!!

That was the problem, replaced it and went for a ride ...... now when taking off from a dead stop, it launches hard and causes the ASB to engage where before with the ASB off, it was a dog and wouldn't even turn a tire!! $60 at NAPA. Thanks Griff!!!

edit; forgot to add, it still is less than impressive when punched from 37+, but I found that the reason is this is normal because at that speed if low kicked in I would be right at 5600 rpm, I put it manually in low and ran it up to 37 mph, yep 5600+ rpm, so the tranny was saving me from myself :Roll .

[TODD L GRIFFITH]

Glad to hear it. One thing also to add is, do not use the 4L60E to downshift and never flush the transmission if it has over 75000 miles. A word from the wise!

[sothpaw]

Why not flush? Why not keep changing the filter and fluid?

[TODD L GRIFFITH]

You can still change the filter fluid by dropping the pan and changing out the filter, but a flush after 75,000 miles has caused the 4L60E to start slipping. A flush is done by extracting fluid using a pump, and adding fluid in the drop tube until the fluid has the same color as what is added. It is not recommended to do this on a higher mileage 4L60E. Alot of transmission shops and dealers offer a flush. The existing fluid in the converter has certain properties due to wear, that the new fluid does not have.
Edit: I have added a link that other people have had problems, myself included. I ended up rebuilding mine. http://www.ls1tech.com/forums/archiv...x.php/t-150948