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Tranny Woes

wolfpackjeeper

wolfpackjeeper

NAXJA Forum User
Location
500' and 500KCAS, RAF lakenheath
Drove the stroker jeep from Hickory NC to Pensacola FL today and Had some interesting problems. The motor Ran great, but the tranny was giving me a lot of problems.

1991 4.7 aw4 4wd, turning 33" BFG ATs.

Around town it is great. Once you get into any sort of steady throttle cruise it fluctuates the power and RPMs by about 200 RPM for a while. Surges and really messes with the truck.

I replaced the TPS and the tranny is full. Dipstick pulls a clean fluid with good color and normal odor. It does this regardless of gear selection, in both Drive and 3rd.

I was thinking it was either internal tranny, possibly the Trans control box thing, or the Torque Converter giving up.
 
What I did when my aw4 was screwing up is: you can unplug the power to the tcu (transmission computer) The fuse is in the engine compartment if its a pre '96. With no power to the tcu you can shift the trans manually, just wont be able to use 2nd. This will allow you to determine if your problem is electrical or mechanical. You may have a bad VSS (vehicle speed sensor)I hope this helps, good luck
 
Also check those solenoids...someone will be along at some point with the link. Mine was doing that (and skipping 2nd) and it was bad solenoids, probably from heat.
 
moneypit said:
Sounds like the TC is locking and unlocking erratically. I'd say it sounds like solonoids, but I have yet to diagnose my own lockup issues so what do I know?

What transmission fluid are you running?
Click to expand...


X2

You mentioned the tire size. What about the gear ratio, load, speed, road surface (flat or incline), how much do you pedal it.

My AW4 used to do that on the highway at certain speed;.. as if the AW4 did not know whether to go to OD or not. A re-gear fixed it. Yours may not be the same as mine was but a 200 RPM sound more like the OD (torque converter) solonoid ascillating between on and off.
 
some of it was defiantly a gearing issue, but that falls in a pretty narrowly defined speed RPM range, I got that part figured out.

I am running 3.55s, I know I need to up them, but the new torque band of the motor made it very bearable, about like driving stock again. The road surface was flat and smooth for the most part, with gentle grades. It was I85 between NC and FL.

I had forgot about the speed sensor, but with the way it was acting, I think it has to be tranny related. l guess I will find an excuse to run out today and pull the fuse before I go.

And it did seem very much like the TC oscillating, plus the trans tunnel was HOT
 
Sounds like TC lockup. Have you checked the brake pedal switch?
 
Goatman said:
Sounds like TC lockup. Have you checked the brake pedal switch?
Click to expand...


no, what am I looking for? I did just replace the Dual booster I had swapped in. The Jeep sat for a few months and the one I had installed failed.

I would expect the speed sensor to cause problems, but why the brake sensor? How does it affect lockup?
 
Good point Goatman. I forgot that switch.

The break light switch also de-activates the lockup for the torque converter. An easy way to test it is to press the breaks lightly when driving at normal speed and the AW4 in OD. When the break is applied, the OD solonoid in the AW4 should loose power thus de-activating the OD.

Check to see if the break pedal when at rest pushes against the switch located halfway down the pedal. Pull back on the pedal lightly to see if this is the problem. There is a way to adjust it should it need adjusting. Some who have done it will chime in.

With the OD not working could also cause the AW4 to get hotter.
 
tapping the brakes stops the oscillation. Brake lights are not on at rest, and the switch and pedal do not appear to be making contact.

Speed sensor is shot BTW. Just never had this problem before when it was garbage.

side note: in a 100mi section of my road trip to florida, my odometer would regularly read only 84 mi. Fun. Time for gears and the adjustment gear for the VSS
 
If you swapped in the dual booster that is reason enough to adjust that switch. My TC wouldn't lock up at all after I swapped to the dual booster, so I had to mess with that switch. It was so long ago that I don't remember if there are two brake switches or just one.

Something to check, since you said only in 3rd and 4th, so it's the TC lockup.
 
wolfpackjeeper said:
tapping the brakes stops the oscillation. Brake lights are not on at rest, and the switch and pedal do not appear to be making contact.

Speed sensor is shot BTW. Just never had this problem before when it was garbage.

side note: in a 100mi section of my road trip to florida, my odometer would regularly read only 84 mi. Fun. Time for gears and the adjustment gear for the VSS
Click to expand...

In addition to the speed sensor in the tail housing of your transfer case. You also have a VSS on the back of your aw4. It uses a magnet unlike the speedometer censor that uses a plastic gear.
 
It has two? I have never removed the tranny in 2 engine swaps so I had no idea it was back there. So which one would be bad. My speedo does not work/ fluctuates around until the vehicle gets warm.

Correction: The brake pedal and brake switch do make comtact at the top of the pedal travel, but that makes sense because the pedal turns the lights off at the return to the top position right?
 
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