I'm having a developing problem with the automatic transmission in my 96 4.0L.

Last winter, when the temps dropped below zero degrees, I noticed the tranny would not shift to 4th until I was about a mile or more from my house on a 55 mph highway. The shift seemed to come only after the engine temp guage was registering, but before full heat was indicated. I often allow the engine to warm for 4-5 minutes prior to driving off on really cold mornings, but even if the engine if fully warmed, the transmission will not shift into High until I have driven about a mile or so. HOWEVER, the warmer the engine is from warminmg up at idle, the sooner it will finally decide to shift up once i start driving. Anyhow, with the return of warmer weather, the problem stopped.

Now that it's getting cold again, the problem is starting up again, but now it is doing it in warmer air temps http://www.4x4central.com/ubb/frown.gif . Last night it got down to maybe 32 degrees, and it did it this morning.

BTW, it's not the OD that's failing to shift, it's fourth gear. I can toggle it in and out of OD before it finally warms enough to shift to High, so it looks like it is not the OD.

Once it shifts to High, I do not have any further problem that day. Or at least until today when it did it when I left work to come home...damn...yep, it is getting worse.

There is no slippage or any other apparent transmission faults.

I checked the ATF level two weeks ago, and it is normal.

So, I'm guessing I either have some sensor that's failing, or I have a trannny that's got a problem.

Before I approach the dreaded transmission repair shop, I wanted to see if anyone on the board might have some thoughts on the possible causes for this slow shifting.

------------------

ERIC H.
"You can run, but you can't hide...my dogs track."

Some additional info:

This morning it was 20F outside, so i let the engine run for almost 15 minutes before driving. There was NO problem with shifting.

However, when i drove it 4 hours later (outside air temps now in the 40s, but drivetrain completely cooled), it went 1/2 mile before shifting to high.

Obviously, temperature is a controlling factor. But temperature of what....the tranny fluid or the engine?????

And is it likley a faulty sensor that isn't reading the temps correctly, or is it something in the tranny mechanics?

------------------

ERIC H.
"You can run, but you can't hide...my dogs track."

I'm confused.Need more info......

Is yours the 4.0OHV or the 4.0SOHC?

If it is the OHV, the only fourth gear would be overdrive. If it is the SOHC, which gear are you calling "High?" If there were no fourth gear, there would be a total of three gear changes. The five speed is actually a three speed with two torque converter lockups: One between 1st and 3rd,(which we feel as second) and one after fourth to fifth. On the OHV with a four speed, the only torque converter lockup is after third for overdrive. If you have the five-speed, and it's not making the 2-3 shift (what we feel as the 3-4 shift) I would guess something inside needs to be adjusted. Maybe Slow-Demon could give a more definitive answer, but that's my best guess.

-Joe-

Rick.... got a server error. Please delete this post.

[This message has been edited by gijoecam (edited 11-03-1999).]

Rick.... got a server error. Please delete this post.


[This message has been edited by gijoecam (edited 11-03-1999).]

Joe, if the overdrive is turned off, it is the final shift. And, yes, my mistake...this is a three speed PLUS overdrive.

Question is, why is this temperature dependent? Doesn't that sound like a transmission temp sensor problem?

There is absolutely no other detectable tranny problem. And once it makes that shift, there is no recurrence until the engine is shut off and the whole system cools down (several hours, depending on outside temps.)

The owner's manual does say the tranny will shift to a lower gear when internal temps are low, but this "problem" seems to be getting "worse"...fortunately, very slowly, so far.

------------------

ERIC H.
"You can run, but you can't hide...my dogs track."

It is temperature related. Your tranny cooler is in the radiator. When your engine is not real warm, the fluid is not warm in the trans either. Because it is 3rd gear only, I would suspect you have a sticky valve in the valve body. This only becomes a problem when the fluid is not thinned from heat. Thus, it isn't real sticky. You can go to a trans shop, or you can put up with it. It probably won't cause any other problems with the trans..... as it is a valve body problem. If the solenoid were bad, I would think that it would always do it...... not just when cold. Just some food for though.

I'm thinking my problem falls into the same category as above, but let me know if I'm wrong.

This morning, it was 44 degrees F in the garage and 34 degrees F outside. I didn't notice any problem when I first backed out, but due to a garbage truck blocking the far end of my alley, I had to pull back into my garage to change direction (One of the fun aspects of living in the city and parking off of alleys). So when I shifted from drive to reverse again, it dropped right out of drive and then took a full 6 seconds before shifting into reverse. I tried it a couple of times when I got outside to make sure it wasn't a one-time thing. And it consitantly took the full six seconds to kick into reverse from drive.

Now that I think about it, I probably should have tried going from park to reverse, but since I didn't notice it when I first got in, I'm thinking there isn't a noticeable delay. I thought about, but forgot to try it again after I pulled into work and everything was warm. So, I know it isn't much to go by, but any input would be appreciated. Thanks.

These Trannie's are programmed to do this guys. The computer delays the 3-4 shift till a certian engine temp is acheived. This allows the engine to warm faster, and thus warm you faster!! It is no to worry about.;)