whats going on with my transmission??

im just trying to see if anyone has experienced this before. my 1990 automatic hs been shifting very strangely lately sometimes, but not aways it will jump back and forth between about 500 rpms a few times per second as if it cant choose between two different gears. i know it probably has something to do with the fluid that im in the process of flushing. when i broke a cooler line a month and a half ago the dumbass at sears gave me some off brand of ford type f to fill it back up with, then i flushed what i could and kragen gave me atf+4 but now im reading i should use dexron 3/ mercon.
anyway, it seems to do this at freeway speeds and usually will jump back and forth between like 2100 and 25000 rpms sometimes it will do this on flat ground when im cruising at about 40mph. i really hope its not the torque converter, it doesnt really have any kind of pattern to when it does this, but it does tend to do it more when im accelerating on a hill.
also is there a way to completely flush the torque converter without geting into the bellhousing?
and im also looking for advice on reading the dipstick. the fluid always looks so thin that i cant really tell if its on the dipstick or if its just thick residue, it looks very light pink not thick and red like it does when you poor it from the bottle, and i know that it thins when it gets hot but it just never looks like theres much on the dipstick but if i read where the thin fluid is registering then apparently my transmission is a little overfilled.

Reading the dipstick right is critical. It's best to look at both sides, check it several times. If the fluid doesn't look right, flush it out. Disconnect the return line on the trans, shove a hose over the end of the fitting into a bucket. Fill it about an inch overfull on the stick with the engine off. Run it a few seconds, kill it, top off. Put about 12 quarts through this way. It's helpful to move the shifter through all the gears as you do this.
Pink fluid is usually an indication of water intrusion. Overheated fluid is a little darker than normal.
See how it does with some new fluid and check back.

The AW4 must have dexron. MUST have it.

KH

Verify fluid level and be sure it is all fresh.

Still symptomatic? Test AND adjust your throttle position sensor (TPS). You will need a meter and a manual. The TPS is adjustable on a 1990 and it has a direct relationship to transmission performance.

I'm having similar problems with my 96 with aw4. I flushed/refilled transmission with dex/merc and fluid is proper level/color. I've fiddled with the TPS quite a bit and doesn't seem to make a difference. The big problem occurs on the interstate. It seems to not be able to decide between staying in overdrive and down shifting. Especially when peaking a hill and beginning decent. (Being under a load, then lightening it) The only partial cure I have found is to accelerate hard to over 50, then it seems to do fine, until i drop back below 55 and it persists. I've been told it could be the torque converter control.. I really hope not. My abs light is on, and I have somewhat of a skepticism this could be the problem. If anyone knows anything about this, i would appreciate the hell out of information. Might even mail you a 12 pack. Thanks

1996redxj said:

I'm having similar problems with my 96 with aw4. I've fiddled with the TPS quite a bit and doesn't seem to make a difference

Click to expand...

What do you mean "fiddled with the TPS"?

The ONLY way to verify proper throttle position sensor is to test it. You will need a manual with the procedure and an analog meter to test it properly. Look for a smooth sweep all the way through while exercising the throttle. I'd recommend doing this first.

Your ABS light shouldn't be related. You don't mean the "check engine light" is on do you? If so, pull codes immediately for guidance and post the exact code(s) here for comment.

Whoops. mix up there. NOT fiddling with the TPS obviously. My bad. I meant the TV cable. Early morning and exams=fried brains.

and no. i meant the abs light. I read a while back about a similar incident where a guys break sensor was messed up and it was telling his transmission to shift down. Thats what was in that writeup anyway. Probably mutually exclusive. I tracked that problem down earlier today. My sensor on the front left hub is gone. Somewhere on a trail i assume.

1996redxj said:

I'm having similar problems with my 96 with aw4. I flushed/refilled transmission with dex/merc and fluid is proper level/color. I've fiddled with the TPS quite a bit and doesn't seem to make a difference. The big problem occurs on the interstate. It seems to not be able to decide between staying in overdrive and down shifting. Especially when peaking a hill and beginning decent. (Being under a load, then lightening it) The only partial cure I have found is to accelerate hard to over 50, then it seems to do fine, until i drop back below 55 and it persists. I've been told it could be the torque converter control.. I really hope not. My abs light is on, and I have somewhat of a skepticism this could be the problem. If anyone knows anything about this, i would appreciate the hell out of information. Might even mail you a 12 pack. Thanks

Click to expand...

yeah, that sounds like what mine is doing and if i accelerate harder, it will stop.
the abs sensor problem reminds me, im not sure if this could be related but the part time 4 wheel drive light gets stuck on or flashesoff and on a lot.

sounds like ours is the same problem. My part-time light doesn't flicker, but the harder acceleration seems to force it back into overdrive. I unplugged the transmission computer and let the residual power drain. That didn't help either. I hope its not the torque converter/control, but if it is.. Good excuse to go ahead and swap it to a manual and be done with all this BS.

1. How to read an automatic transmission dipstick--remove the dipstick and take a small jewelers or gunsmiths file and use the edge to make hash marks on the dipstick. They will help show where the fluid is. An alternative, wipe the dipstick and then hit it with a black magic marker, the contrast will help.

2. One of the first things to do with the AW4 is to un-plug the TCU and drive it shifting manually. You will have 1st in 1-2; 3rd in 3; 4th in D; park, neutral, and reverse. If it shifts Ok with the TCU unplugged, then the problem is electrical in nature. If it does not shift Ok, then the problem is hydraulic/mechanical.

3. Electrical problems--TCU in line fuse; TCU; TPS; soleniods; brake switch; associated wiring and connectors; NSS--not just a safety switch, it also provides data to the TCU.

4. Don't forget to adjust the throttle body pressure cable.

1996redxj said:

and no. i meant the abs light. I read a while back about a similar incident where a guys break sensor was messed up and it was telling his transmission to shift down. Thats what was in that writeup anyway. Probably mutually exclusive. I tracked that problem down earlier today. My sensor on the front left hub is gone. Somewhere on a trail i assume.

Click to expand...

On the Renix Jeeps, there is a separate brake pedal for the trans computer that tells it to unlock the torque converter. It can get gunked up and not close, so the trans computer thinks you've always got the brake on and hence never locks up the t/c.

lawsoncl said:

On the Renix Jeeps, there is a separate brake pedal for the trans computer that tells it to unlock the torque converter. It can get gunked up and not close, so the trans computer thinks you've always got the brake on and hence never locks up the t/c.

Click to expand...

i would like to learn more about this how do i know where t look to fix this.

lawsoncl said:

On the Renix Jeeps, there is a separate brake pedal switch for the trans computer that tells it to unlock the torque converter.

Click to expand...

fixed that for you.

What he meant was, there are 2 switches on the brake pedal. one controls the brake light, the other feeds to the trans. control computer.

There are different versions of switches on the Renix.

Some have a plunger type cruise control switch mounted above the brake lamp switch that has a vacuum line attached, and some are incorporated into the brake lamp switch w/o the vacuum line.

Either way, the brake light switch feeds C10 on the TCU, and so do the cruise control switches.

I had a similar issue with a 91 xj shifting erratically. it tended to happen more on hills. ended up that the TPS sensor wiring had an exposed area and was shorting out on the manifold. had a bad o2 snesor at the time too. was a real pain until i found the short

If your speedo needle wiggles it could be sending an inconsistent signal to computer causing Torque converter to cycle on and off. The vehicle speed sensor get its reading from from speedo cable. When you experience the problem try to put your left foot on brake pedal lightly without lifting off the throttle. That will turn off the converter.

JJacobs said:

Reading the dipstick right is critical. It's best to look at both sides, check it several times. If the fluid doesn't look right, flush it out. Disconnect the return line on the trans, shove a hose over the end of the fitting into a bucket. .

Click to expand...

will this drain the torque converter also, or is this just how you prefer to drain the trans ?

Draining the trans is done with the drain plug and only gets a couple quarts. This is flushing the whole transmission, basically the same as what you get with a high dollar flush machine but it's not quite as elegant.

lawsoncl said:

On the Renix Jeeps, there is a separate brake pedal for the trans computer that tells it to unlock the torque converter. It can get gunked up and not close, so the trans computer thinks you've always got the brake on and hence never locks up the t/c.

Click to expand...

ok so when i lightly compress the break pedal it acts like the tc unlocks and it allows the tranny to rev higher does this sound normal?