DasWulf79

I finally started driving my Cherokee more and the transmission will run great, then it will occasionally start kicking into passing gear when between 45-50 mph. I am guessing its passing gear anyways. The RPMs will jump up to about 3500. I haven't driven this Jeep much and it sat for about 2 1/2 months while I did some work on it. I did replace the NP242 in it as the one that came with it had a cracked housing. The transmission shifts smoothly and runs good, doesn't buck or jerk. I know for a fact that it needs to be serviced. Any info would be helpful. Thanks!

DasWulf79

After a day or so of driving it, it stopped doing this. I'm thinking maybe it was trash or sludge in the valve body from it sitting up so long.

tjwalker

Then service it. Transmission fluid wears out similarly to oil.

Get some fresh Dex/Merc III compatible fluid in there.

I'd recommend dropping what is in the pan and replacing the 3-4 quarts required.

Replace until fluid stays RED and does not smell BURNT.

67 GMC

Mine is doing this intermittantly. I think it's the speed sensor. The sensor reports 0 speed, which tells the TCU to go to first gear. I've installed a toggle switch on the dash to turn the TCU off when this happens. Then you can drive it like a manual. Seems to only happen when the trans gets hot.

The TCU counts the pulses from the speed sensor to see what gear you should be in. If it doesn't get any, it thinks you are stopped, so it shifts to first. I monitored my speed sensor output and this is what's happening to me.

DasWulf79

Well yeah I am going to service it, I just haven't had the time with work and everything else. I used to be an R&R Mechanic at a transmission shop and kinda picked up a few bits of knowledge while there. The Jeep isn't my daily driver right now, I'm just fixing it up for now, so the service just hasn't been high on my priority list. The fluid in the pan right now isn't too bad looking and it isn't burnt or varnished. When I get time I am gonna service and flush it with a hot flush machine.

DasWulf79

Ok well I finally got enough of a break from work to get back to this issue. It also had started to act really funny when driving 45-55 mph. It would rev to 3500 rpm's and stop pulling, and I ould have to pull over for a minute or so and it would act ok for a few miles. I didn't know when the tranny had last been serviced like I had said before so I thought possibly the filter was clogging. I finally dropped the pan and it was surprisingly very clean, no metal shavings or clutch or band material. There was a date of 4/21/11 written on the bottom of the valve body. When I used to work as an R&R mechanic at the transmission shop I knew the rebuild mechanics would write the date of rebuild on the valve bodies sometimes. So i figured at the least it was serviced last April. I went ahead and changed the fluid and filter, but it still acted up really bad and stopped shifting all together. I finally tested the TS and VOILA!! I got a reading of 4.68V for the input but 0.00V for the output. Changed and adjusted the TPS yesterday and she now drives like a totally different vehicle. 100% improvment!!! I know from the tranny shop that the TPS can make the tranny act up, but I have never heard of it making it act up as bad as mine was. Thanks guys for all your help and input.

Rustydog555

Tps can cause shift problems but if it's downshifting to first at speed I'd say speed sensor if its slow to up shift tps

cruiser54

TEST the trans side of the TPS.


RENIX TPS ADJUSTMENT
Before attempting to adjust your TPS be sure the throttle body has been recently cleaned. It's especially important that the edges of the throttle butterfly are free of any carbon build-up.
IMPORTANT NOTE: With the Key OFF, and using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS. The letters are embossed on the connector itself. Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it parallels the valve cover and also over near the MAP sensor on the firewall. If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, some modifications to the sensor ground harness will be necessary. The harness repair must be performed before proceeding. I can provide an instruction sheet for that if needed.
MANUAL TRANSMISSION:
RENIX manual transmission equipped XJs have only a flat three-wire TPS mounted on the throttle bodyand it provides data input to the ECU. It has three wires in the connector and they're clearly embossed with the letters A, B, and C. Wire "A" is positive. Wire "B" is ground. Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors. Note the voltage reading--this is your REFERENCE voltage. Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts. Loosen both T-20 Torx screws attaching the TPS to the throttle body and rotate the TPS until you
have achieved your desired output voltage. Tighten the screws carefully while watching to see that your output voltage remains where it is supposed to be. If you can't achieve the correct output voltage, replace the TPS and start over.
Sometimes, after adjusting your TPS the way outlined above, you may experience a high idle upon starting. If that happens, shut the engine off and reconnect your probes to B and C. Start the engine and while watching your meter, turn the TPS clockwise until the idle drops to normal and then rotate it back counterclockwise to your desired output voltage.
AUTOMATIC TRANSMISSION: RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a flat three-wire connector, same as the manual transmission vehicles have, and it is tested the same as the manual transmission equipped vehicles, as outlined above—FOR ALL ENGINE MANAGEMENT RELATED ISSUES.
However, the automatic TPS also has a square four-wire connector, clearly embossed with the letters A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module. THIS SQUARE FOUR WIRE CONNECTOR IS USED FOR TRANSMISSION/SHIFTING RELATED ISSUES ONLY. Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your REFERENCE voltage. Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage. For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage. If you can't, replace the TPS and start over. So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and the other side feeds the TCU.
FOR AUTOMATIC TRANSMISSION RELATED ISSUES: Check the square four-wire connector side of the TPS.
If you have ENGINE ISSUES check the flat three-wire connector side of the TPS.
For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
Revised 09-22-2012

DasWulf79

I drove around 150 miles since I changed and adjusted the TPS and its running great. No more issues at all.

cruiser54

Glad to hear of your success.

Black89

Sorry to dig up and old thread but mine seems to be doing the same thing at @ 45 to 50 MPH. I have replaced the TPS and it's set correctly. I have also cleaned and installed a new fuse for the TCU along with cleaning the TCU plug and the ones by the dip stick. Tranny fluid is good and it only recently started doing this. I'm wondering if my TCU is bad? For got to add mine is an 89' 4.0 Auto.

Black89

Black89

Say will tire size affect the way the TPS is set? I set mine to .830 but my tires are 235's and not the factory recommended 205's. should I raise the TPS reading to say .835 or so? would that maybe get rid of the shifting issue that i am seeing?

Black89

cruiser54

TPS has 2 sides. One for the engine and one for the trans. Absolutley independent of each other. Sounds to me like you're adjusting the TPS on the "engine" side for a problem that's on the "trans" side. Hopefully this helps you:

Tire size has no bearing on this bTW.

RENIX TPS ADJUSTMENT
Before attempting to adjust your TPS be sure the throttle body has been recently cleaned. It's especially important that the edges of the throttle butterfly are free of any carbon build-up.
IMPORTANT NOTE: With the Key OFF, and using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS. The letters are embossed on the connector itself. Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it parallels the valve cover and also over near the MAP sensor on the firewall. If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, some modifications to the sensor ground harness will be necessary. The harness repair must be performed before proceeding. I can provide an instruction sheet for that if needed.
MANUAL TRANSMISSION:
RENIX manual transmission equipped XJs have only a flat three-wire TPS mounted on the throttle body and it provides data input to the ECU. It has three wires in the connector and they're clearly embossed with the letters A, B, and C. Wire "A" is positive. Wire "B" is ground. Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors. Note the voltage reading--this is your REFERENCE voltage. Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts. Loosen both T-20 Torx screws attaching the TPS to the throttle body and rotate the TPS until you
have achieved your desired output voltage. Tighten the screws carefully while watching to see that your output voltage remains where it is supposed to be. If you can't achieve the correct output voltage, replace the TPS and start over.
Sometimes, after adjusting your TPS the way outlined above, you may experience a high idle upon starting. If that happens, shut the engine off and reconnect your probes to B and C. Start the engine and while watching your meter, turn the TPS clockwise until the idle drops to normal and then rotate it back counterclockwise to your desired output voltage.
AUTOMATIC TRANSMISSION: RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a flat three-wire connector, same as the manual transmission vehicles have, and it is tested the same as the manual transmission equipped vehicles, as outlined above—FOR ALL ENGINE MANAGEMENT RELATED ISSUES.
However, the automatic TPS also has a square four-wire connector, clearly embossed with the letters A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module. THIS SQUARE FOUR WIRE CONNECTOR IS USED FOR TRANSMISSION/SHIFTING RELATED ISSUES ONLY. Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your REFERENCE voltage. Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage. For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage. If you can't, replace the TPS and start over. So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and the other side feeds the TCU.
FOR AUTOMATIC TRANSMISSION RELATED ISSUES: Check the square four-wire connector side of the TPS.
If you have ENGINE ISSUES check the flat three-wire connector side of the TPS.
For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
Revised 09-22-2012

cruiser54

Also, have you done my recommended ground refreshing? Trans plug refreshing? Posts #1 and 10 in the link in my signature.

Black89

I was testing at the Tranny side. Before I put in the new TPS it was shifting up and down @ the 30 to 35 MPH range. Now it's searching @ 40 to 45. I don't have the numbers I originally wrote down with me but I think my input voltage was only like 4.6 or so. I've cleaned every plug under the hood and such and I'm thinking I may need to do the grounds to see if I get can the input voltage back up and then reset the TPS. It's seems to be worse in OD and not so bad in 3rd.

Black89