The old winter car 98 Lesabre has been acting up recently. Monday when a few miles from home it started going between gears upshifting and downshifting and giving a decent clunk when starting from a dead stop, Checked the Trany fluid level and it was not low, A bit over full. It sat in the yard for maybe an hour, and I took it for a ride, It worked perfect. Tuesday it worked fine till 10 miles from home and did the same thing. I went slow and made it home No problem. When this happens the cruise control never works. Today the transmission worked well, the cruise did go out for a short time then started to work again.
I had auto zone check for codes and nothing came up but a map sensor because the manifold intake upper has some minor damage causing the sensor to not read perfectly. it idles a bit rough but runs fine past idle. I should just change the intake manifold. It’s not a hard job and is cheap. But that would not be causing the tranny issues. So far, its only done this after running for maybe 30 minutes.
If its the servos inside the tranny I will not be fixing it. I am considering changing the tranny fluid and filter which is easy and cheap. But how likely is that to help?
The transmission pressure control solenoid may fail causing erratic shifting. Our technicians tell us that partial dis-assembly of the transmission is necessary to replace a failed pressure control solenoid.
Yep, the EPC (Electronic Pressure Control) solenoid is a very common failure, caused by the armature sticking, on the 4T65E transmissions, The EPC solenoid fails with no metal contamination, even on a perfectly clean low mileage transmission, and it is behind the side cover on the edge of the valve body, don’t remember if you can change it without removing the valve body or not… It is a part that anytime a builder opens one up, the EPC solenoid gets replaced for the most part…
Sometimes you can floor jack the trans and just loosen the right hand cradle bolts and remove or almost remove the left hand cradle bolts and sneak the side pan off, helps to have a couple of floor jacks… using the floor jack w/block of wood under the trans pan, raise and lower the trans as needed (once mount(s) are loose) to remove the side cover for access to the valve body…
Yeah sometimes they can be a pain, but I found out when doing transmissions daily to spray a little WD-40 etc on the bolt tread greatly helps when reinstalling them…
But you may have been referring to the removal part of it… lol
Picked up some sea foam today. Will see what happens. If that does nothing, then I will try changing fluid and filter and add Lucas. I did just that for the park av and it did help that had kind of similar trany problems.
seafoam didn’t help. I drove yesterday 20 miles it sat for a few hours then drove 20 miles back home no problems. But today drove for about 60 miles with a few quick stops and the last 15 miles the cruise control went out but the tranny was ok until the last 5 miles it did the dropping down a gear and back up. The last 2 miles on back roads i ended up having to go real slow in in 2nd or 3rd gear. It go to the point by this time if you pushed it more it felt like it was starting to slip just slightly. At this point I was going about 30 mph or less so not to push it too much.
Besides the cruise going out the speedometer also starts to bounce around up to 5 miles both ways from the actual speed limit.
I suppose it will try new fluit with lucas and filter.
Tester beat me to it lol, sounds like the VSS is going out, it will keep the CC from working also… The VSS (vehicle speed sensor) is also the transmissions output shaft sensor on the 4T65E, meaning it generates a signal based on the rotation of the output shaft, this signal is crucial for the transmission’s electronic control system (TCM) to manage shifting and other performance aspects, another words, it tells the transmission what the output shaft speed is, if the TCM does not know what the output shaft speed is, then how does it know what gear it needs to be in…
If you have live data you can watch to see if the signal is dropping out when it acts up…
You need to review the Vehicle Speed Sensor signal while driving, unlikely you will see an invalid signal while in the parking lot. Tools are only as effective as the person using them, don’t rely on an Auto Zone clerk for diagnosis.
Yes, loosely speaking, a VSS is like a crank sensor, it might not throw a code even though it won’t start… and yes when a sensor gets hot it can fail…
If you swap VSS sensors, just make sure they are the same part number as the ohm’s value can differ… generally speaking…
Yes, they’re the same part. Looking at this diagram it looks like the best way to get at it is by taking the driver’s side tire off. Could not find any decent youtube videos.
It only pays 0.5 hours, so pretty easy, little harder using a floor jack..
I would take a peak from under hood 1st, might be able to sneak in from behind the engine with a long extension, been a while so don’t remember either way… lol
Is speed sensor, vehicle speed sensor and transmission speed sensor all the same?
Anyways It looks like this sensor is on the passenger side behind the tire. I first found it from above and it looked like the connection was not all the way in. I am not 100% sure on that from that view it’s hard to see and when you have your hand in there your blind. From above I pushed on the connection some. Pulled the senor out and then put it back in. It’s pretty easy to do if you take the tire off.
I am going to test drive tomorrow it to see if maybe it was a bad connection.
