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Specs:  1997 Jeep TJ Wrangler 4.0L with 32RH transmission

Background:  I was driving per usual and after about 25 minutes of being on the road my Jeep began to accelerate on its own and the throttle felt like it was stuck all the way open. It was early, and thankfully there weren't many cars on the road so I kinda blew through an intersection and managed to get off of a main road into a parking lot. I should mention here that I had to ride the brakes while the vehicle was accelerating in order to keep it under control, which I know isn't good for any engine/transmission. I put it in neutral and pulled the parking brake until I was able to get the vehicle to stop. I shut it down and after catching my breath, fired it back up in neutral. It acted like i was flooring it while I wasn't. I assumed that the throttle cable had gotten stuck open somehow, but when I popped the hood I noticed that it was actually the tv cable that had come detached. I popped it back on, and my revving issue got under control, but when I began driving i noticed that the Jeep would top out at around 2500-3000 RPM and roughly 33 mph.

At first I thought I was stuck in limp so I pulled the battery negative and tried again—no luck.  (I later learned that this vehicle does not have a limp mode.)  I decided that I was going to stop screwing around with it and put it in a parking spot—that's when it completely died....At that point I said screw it and had it towed to a local shop.

At the shop:  The power loss/ crank no start was diagnosed as a CPS and the jeep fires right up now. The problem is that it still gets limited out at around 2500 RPM and doesn't go over 33 mph in any drive gear BUT does rev as high as you please while in park/neutral. 

The mechanic has run every computerized diagnostic available, tested the back pressure and assured me that the cat isn't clogged, and is still unsure how to resolve the problem.   I'm thinking that I'll probably end up having to just have it towed back to my house to do the rest of the trouble shooting, but I'm not sure what could be wrong with it.  

All I can think is that when I had to ride the brakes as to not die in the intersection that something got messed up in the trans, or that I blew a seal/ring in the engine and the power output is limited now.  As far as I know the shop has not run a compression test, but it's always one of the first troubleshooting things that I do.

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  • Moses Ludel changed the title to 32RH Will Not Rev Over 2500 RPM or 33 MPH
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Kevin G...Does sound like time to work on this yourself.  I have moved away from scan tools to oscilloscope diagnostics, which increases the mechanical tests that can be performed.  You can do many tests with conventional (mechanical) diagnostics tools.  It never hurts to do a compression check.  Follow that with a cylinder leakdown test to pinpoint the loss of compression in a specific cylinder(s).

Something is "holding the engine back".  You did not specify whether shifts through the gears seem "normal".  Are you in 3rd/direct gear and still not getting over 33 mph, or is the transmission failing to upshift to 3rd gear?

When there is revving up without a vehicle speed response, you have an issue with slippage at the transmission clutches, bands (yes, the 32RH still has bands) or the torque converter.  This does not sound like slippage...When there is a slowing down or speed limitation, you have drag.  This can be a defective converter or—don't overlook this prospect—the brakes.  If the transmission is not the culprit, you could have a master cylinder or hydraulic cylinder(s) locking up the brakes, or the E-brake may be binding and not retracting.  If your Jeep feels like the brakes are on, they may very well be on or dragging.

Make sure the master cylinder piston and brake pedal retract all the way to prevent fluid from being trapped in the cylinders.  You have drum rear brakes, so make sure damaged brake hardware is not causing the shoes to drag.  Make sure the E-brake cable is releasing completely.  You stood on the brakes hard, there may be something bent or binding.  Make sure each wheel rotates as soon as the brake pedal is released.  Look for broken brake parts, bent shoes or loose shoe lining.  If brake lining was low and self-adjusters could not compensate, wheel cylinder pistons and actuator pins may be coming out of the cylinder(s).  With the vehicle in the air or off the ground, with the engine shut off and transmission in Neutral, make sure wheels rotate freely and the driveshafts turn freely as well.

If the drag is not brake related, I would consider torque converter damage.  If the engine is not over-revving or flaring up in speed under load, and if vehicle's speed is limited, the torque converter could be damaged.

Let us know what you find...

MosesMoses 

 

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Awesome info thank you.  It almost feels like the vehicle is starting off a gear.  By this I mean that acceleration is slightly slower to 33 than it had been before this incident.  It may not be noticable to someone that had never driven the vehicle, but it's obvioust o me.   I can tell that there is 1 distinct gear change, but not another.  If I manually shift from 1 to 2 there is an obvious difference, so it may mean that it's not shifting into 3rd. 

I hadn't considered the brakes, and will check into those as soon as I end up getting it back. I didn't really smell burnt pads or shoes, but I will absolutely check for any bindage as that's a much easier fix than pulling the trans to replace the converter.  It's at 199,3xx miles too so something like this was bound to happen at one point or another.  A guy here just parted out his 97 with 130k on it and sold the trans for like 200 bucks...Oh how I wish I'd known.  

It's been a week, and although the mechanic is a good guy and not charging shop time to diagnose the problem I'd like my jeep back on the road this summer.   

 

Thank you again for the insight

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Kevin, I would start with the brake system as I described...E-brake cables would be my first check.  Remove the rear brake drums next.  Assess from there.  E-brake drag would be uniform and likely not cause a left or right pull.  An individual wheel brake issue or drag would likely cause a pull.

Likely the transmission survived the ordeal unless there were wear symptoms before the event.  If the transmission is okay, and if the bands have not been adjusted in a while, I would treat the transmission to a fresh filter/fluid change and a band adjustment by the FSM: preventive care.

Let us know your findings...

Moses

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  • 2 weeks later...
On 7/14/2021 at 7:00 PM, Moses Ludel said:

Kevin, I would start with the brake system as I described...E-brake cables would be my first check.  Remove the rear brake drums next.  Assess from there.  E-brake drag would be uniform and likely not cause a left or right pull.  An individual wheel brake issue or drag would likely cause a pull.

Likely the transmission survived the ordeal unless there were wear symptoms before the event.  If the transmission is okay, and if the bands have not been adjusted in a while, I would treat the transmission to a fresh filter/fluid change and a band adjustment by the FSM: preventive care.

Let us know your findings...

Moses

 

Moses

Okay, so I've been travelling for work and haven't had much time to tinker, but I finally threw in the towel with the mechanic and just picked the jeep back up the other day. 

Here's what I've learned: 

The compression numbers are all between 125-135 so I believe that the engine is in decent shape.  This was done by the shop, but confirmed by me. 
The brakes are not sticking or dragging.  
The mechanic adjusted the bands and connections while it was in his shop
The fluid is really only a few thousand miles old and does not smell or look burt at all.  

I live in a rural spot so I decided to say screw it and take it for a ride knowing that I may end up needing a ride home and I'm 99% sure that it's beginning in second gear or has lost first.  Initially I noted that it was maxing out at 30ish miles per hour, but that was only after a very small amount of driving.  Taking it on a longer ride has shown me that if i feather the gas a little bit when it's at the 30mph range, I can coax it into 3rd gear.   As long as it's in 3rd it will drive and accelerate as it always did, but when it's slowed down or stopped the process starts over with it beginning in (what I believe to be) second.    The fact that it's not at all trying to catch first is worrisome, but before I pull it apart I'd like to attempt anything else that may pop into your mind.  

 

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Kevin G...The compression numbers are "okay", as expected for the mileage.  The good news is that the high-to-low is relatively uniform, within 10 PSI is less good.  If you're not using oil, rattling or knocking, the engine is sound for now. 

Based upon the transmission symptoms you share, here are the FSM possibilities...You should have the FSM (at least an inexpensive eBay CD or download version), and this information is available in the FSM for your model Jeep TJ:

No Low Gear (Moves in 2nd or 3rd Gear Only):

1)  Governor valve sticking:  Remove governor, clean, inspect and repair as required.

2)  Valve body malfunction:  Remove, clean and inspect.  Look for sticking 1-2 shift valve, 2-3 shift valve, governor plug or broken springs.

3)  Front servo piston cocked in bore:  Inspect servo and repair as required.

4)  Front band linkage malfunction:  Inspect linkage and look for bind in linkage.

No Kickdown or Normal Downshift:

1)  Throttle linkage misadjusted:  Adjust linkage.

2)  Accelerator pedal travel restricted:  Floor mat under pedal, accelerator cable worn or brackets bent.

3)  Governor/valve body hydraulic pressure too high or too low due to sticking governor, valve body malfunction or incorrect hydraulic control pressure adjustments:  Perform hydraulic pressure tests to determine cause and repair as required.  Correct valve body pressure adjustments as required.

4)  Valve body malfunction:  Perform hydraulic pressure tests to determine cause and repair as required.  Correct valve body pressure adjustments as required.

5)  Valve body malfunction:  Sticking 1-2, 2-3 shift valves, or governor plugs.

What I would do is backtrack to what you initially encountered:  a disconnected TV cable.  Perform a TV cable adjustment and make sure that the TV cable is connected on the inside of the transmission.  Check the function of the TV cable, making sure that the TV cable is actually moving the throttle valve at the valve body.  If in doubt, replace the TV cable.

If that isn't the fix, start where two symptoms/malfunctions overlap.  The governor and the valve body overlap, but don't start with the extra work of removing the valve body for cleaning and inspection.  Start here:  You want to know the relationship between a functional transmission, a loose TV cable and the subsequent malfunctioning shifts.  If and when necessary, the governor and valve body can each be tested by running hydraulic pressure checks according to the FSM procedure.  I made you a PDF copy of the FSM coverage.  You can zoom into the document for easier reading.  The converter stall test and clutch air apply tests are included:

30RH-32RH Pressure Checks PDF.pdf

Pressure testing is a good diagnostic tool.  You will need an automatic transmission pressure gauge to follow through with these tests.

Moses

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