4L60E transmission question ....

we were on about a 200 mi trip to go see our grandson wrestle,(94 yukon 4x4 350 and 4L60E I think) half way there on the interstate,boggieing with the cruse on at about 80.. then all of
sudden, the tach needle shots up and the MPH needle go down,,as I pulled over, it did not down shift,nor would it shift gears,so we slowly drove back to the nearest town, called my son to come trailer us home. while waiting and sitting (about an hour and half) it started working again,:HMMM:what would cause that?/:confused::confused: a friend has a 4L60E for sale but it's not off a 4x4, would that fit my yukon :rolleyes: thanks in advance...

These vehicle had problems with the ignition switch. There is an ignition feed to the fuse box that has the cluster and transmssion control on the same circuit. Usually this will happen on vehicles with a tilt column. As you tilt the wheel up and down the wires are moved that go to the ignition switch. I doubt you have an internal trans issue. Have the engine scanned first. One other thing that will cause problems is the vehicle speed sensors at the trans. The best thing to do is monitor both input and output shaft speeds while driving. This could explain speedo acting up also

Scott

This one's easy.....
There is a sensor in the transmission that sends a signal to the engine computer as well as the speedo. It can be reached from the outside of the tranny case and removed with a socket.
The engine computer also sends a buffered signal to the tach.
It's a cheap part and mine was temp sensitive. It would open up when hot and the transmission would not shift out of first gear or down to first gear if you were going fast when it failed.
Also, the tach went nutz and the speedo dropped to zero.
It's a common part and takes about 10 minutes to replace.
I'd bet that's the problem.
I replaced mine after what you described and haven't had a lick of trouble since.

It has a molded plug with just two wires. The sensor has an "O" ring on it to keep tranny fluid from leaking but the fluid level is below the sensor so you don't have to put a pan underneath.
This problem drove me nuts for about a year before I had a solid failure. Then it was easy to trouble shoot.

Good luck,
DT

Mine did that after a manual downshift entering the highway on a ramp...after it was shut off and re started it worked fine... I was told it was computer related.. That was several years and many miles ago...I never downshifted it again after that.(from 3 to 2)

guys thanks for the info, but I went to the parts store,just as well have gone
to a book store,they did'nt know what I was talking about, can anyone
tell me where about this sensor is,(on tranny or transfer case?? and which side) it's being working fine in town but I do need to go out of town in
a couple of weeks, so any info. would be very helpful. thanks..

I think it's on the right side of the transmission. It can be reached on my car without to much trouble.
Just unplug the molded plug and remove the single mounting bolt and it should come right out.
It might be referred to as a speed sensor.
I don't really know what the part number is but a GM dealer should know.
A transmission shop might also.
I'd sure replace it before you go on your trip.
I had to limp home in first gear. It took forever but at least I wasn't stranded.

DT