milkmanzeta

So I'm trying to solve a couple issues with my girl's 1999 V6 RWD JGC...when it starts up, it's fine...runs good until it's a bit down the road and warms up and drops out of the top gear. It can't go fast after that without over-revving the engine. To keep it at a comfortable RPM, it can't go much higher than 60-65...AAMCO said a cracked drum and then quoted me upwards of 2 grand. That's not happening, but I'm willing to attack this on my own and have a lift but I lack real knowledge of transmissions...and I'm not positive that that's even the issue. Any help will be appreciated. Thanks!

dave1123

First of all, is this a 4.0 I6 or a 4.7 V8? It makes a difference because they have different transmissions. The 4.0 uses the 42re and the V8 uses the 46re.

Either way, 3rd and 4th (O/D) are shifted electronically with solenoids controlled by the transmission module or PCM depending on the year. On my '00 WJ, there is a button on the side of the shifter to lock out the O/D. It could be something as simple as a short in this switch wire or the O/D solenoid in the trans. If it engages in O/D at all, there shouldn't be internal damage to the clutches. Your problem seems temperature related.

It may be something else entirely. The PCM senses throttle opening vs vehicle speed and will downshift the trans if the load is too great. This is a long shot, but check your MAP sensor.

At any rate, I think your problem is electrical, not mechanical.

fishbone

How in the world did double A..beep beep..MCO come up with that diagnosis? I can almost guarantee you it's not a drum (very very tiny outside chance). Problem is either electrical or pressure related could also be related to torque converter. As I am at work right now and dont have access to my tech info, I can post some stuff later. In mean time post up the engine info so we get the right trans. Also, do you have check engine light on???

dave1123

Fishbone, right now my 42re has 3 trouble codes set. one for torque converter clutch and 2 for governor pressure (too high and too low) and the transmission functions perfectly, shifts solidly, and the O/D works the way it's supposed to. The governor codes popped on at sub-zero temperatures but haven't caused any malfunctions yet. I'm going to have the codes cleared to see if they return. The torque converter will, but I can deal with that. I just clear that code, lock out O/D, and drive it to my inspector. I REALLY don't want to rebuild the trans if it's working well just to keep the CEL off.

fishbone

Dave I was hoping the OP would have provided us with the proper engine size thats why I never posted anything last night. I'll post up something for ya later on that. Off the top of my memory the governor pressure soleniod would be responsible and not a total overhaul. In your case could be just a freak thing caused by the subzero conditions.

dave1123

I realize that, Fish, but every place I take it for advise want to rebuild it. I quess I'll just buy the governor and convertor solenoids and go from there. I have to change the filter anyway. It's only got 25K on a complete fluid transfer.

Since the pressure codes popped up, I have been starting it and warming it up in neutral for a couple of minutes when it's cold and that seems to improve the shifting. Even now that it's warm outside, I still give it half a minute on neutral to get the pump pressure up before driving away.

The other day, I got into a situation on an entrance ramp that needed extra power. I gave it the boot and it just about snapped my neck because it went down to 1st gear when I was expecting 2nd. Nothing wrong with the clutches!

fishbone

For what reason are they giving you for the rebuild?

fishbone

Dave do you have the specific dtc codes on your issue? I am curious to know if its the governor pressure codes (P1756) and (P1757) or is it the voltage codes (P1763) and (P1764). And do you know if they appeared all at the same time? Same day?

dave1123

They are the electrical codes (P1763 & P1764) but my P0740 is always on. I only know that when the trans acted weird that one very cold day, I checked the codes and the others showed up. I've gotten into the habit of checking the codes regularly since then but haven't found anything else. I need to get this sorted out by the end of August because I have an inspection due then.

The converter lock-up isn't working, but last year I had that code cleared and locked out O/D on the way to my inspection guy. In NY state, your PCM is plugged into the DMV mainframe via the internet so there's no fooling the readout. Now they're saying they won't just clear the codes without doing the work because it's against the law.

Fish, I really appreciate your help, but I think we've stolen this post. Can we help this guy? What would make it drop out of O/D after it warms up? Let us take this to a PM. New topic before we overwhelm the tile system.

milkmanzeta

So she's been getting a check engine light on and off for like a year. Every time she takes it in, either the light is off, the guy is incompetent, or she's not asking the right questions. I took it today and after a bit of highway driving (3 or so hours) I got it to come back on. Stopped by AutoZone and they got a solenoid error.

milkmanzeta

Also, it's the V6 version.

fishbone

In 1999 the available engines were the inline straight 6 cyl or the V8. There was no V6 available. Also, do you have the number of the DTC code that Autozone pulled? There are a few soleniods and would like be sure what we are dealing with here. When you drove it can you tell me was it cycling in and out of overdrive? When it drops out of overdrive does the engine seem to rev really high? The change in RPM really should be subtle and not drastic as technically you can drive without overdrive. Really need to know that code number if you can get it please. Very hard to help diagnose without more information.

milkmanzeta

Yeah, I meant I6. The code was P0783. Here's the receipt:



Thanks for helping me out.

milkmanzeta

Also, yes when I start driving and it's cold, it drives normally. About 15 minutes in, it drops the gear and so the RPMs kick up. I slow down from there...but it goes back and forth for a few minutes and then stays in the lower gear.

fishbone

Ok, that's a lot better information. Can you tell me when it does shift into overdrive, is it clunky? Does it bang hard or is it smooth?