Transmission woes
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Newbie
Joined: May 2019
Posts: 8
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Year: 1988
Model: Cherokee (XJ)
Engine: 4.0 IL6
Transmission woes
So, I have read a lot of posts about transmission issues concerning the TCU, TPS, and speed sensor. I have an 88 with the four speed auto AWD and it will just "drop" out of gear sometimes while I am driving it. Bought it about a month ago from a guy who was shifting it manually, but a simple fuse fixed that problem. It usually shifts fine and I love it, but sometimes it will act like it is stuck in between gears or slipping. I can shut off the motor and.turn it right back on and continue as if nothing ever happened, but that's a pain. Any suggestions where to start? I have new solenoids and a filter coming, but it shifts solid most of the time. Thinking tje.problem lies elsewhere. Thanks
CF Veteran
Joined: Dec 2017
Posts: 4,365
Likes: 1,215
Year: 1989
Model: Comanche (MJ)
Engine: 4.0
Start by checking and adjusting the cable from the throttle body to the transmission. If that's too loose it'll shift sluggishly or even not at all.
Also head over to Cruiser54.com for a collection of excellent tips on common problems with the Renix era jeeps, especially the advice about the grounds.
Also head over to Cruiser54.com for a collection of excellent tips on common problems with the Renix era jeeps, especially the advice about the grounds.
CF Veteran
Joined: May 2012
Posts: 7,965
Likes: 964
From: Lost in the wilds of Virginia
Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
By the way, you really need to clean up your grounds.
Also, see my sig, #1.
On another note, what color is your trans fluid? If it's dark, see my sig, #3.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
RENIX GROUND REFRESHING
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, failed emission tests, and wasted money replacing components unnecessarily.
All the components listed below ground at the dipstick tube stud:
Distributor Sync Sensor, TCU main ground, TCU “Shift Point Logic”, Ignition Control Module, Fuel Injectors, ECU main ground (which other engine sensors ground through, including the Oxygen sensor, Knock Sensor, Cruise Control and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
- Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. If the whole stud turns, you can use a 7/32″ six point socket or wrench to hold it so the nut can be removed. Worst case, cut the wires and remove the stud and nut. Install new terminal eyelets on the wires when going back together. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Surfaces must be clean, shiny and free of any oil, grease, or paint.
- Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Apply a liberal coating of , which is available at Lowe’s and other stores. Reinstall all the wires to the stud and tighten thhttps://i0.wp.com/cruiser54.com/wp-content/uploads/2015/10/dipstick-stud.jpge nut down securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for its intended use and subject to corrosion and poor connections at each end.
- Remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Apply . Reattach securely.
- Remove the other end of the cable from the rear of the head using a 3’4″ socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely with a liberal coating of .
I prefer to add a #4 gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18″ long with a 3/8″ lug on each end works great and you can get one at any parts store already made up. NAPA has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10″ long with 3/8″ terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. NAPA part number 781115.
For those of us with Comanches, it’s very important to remove the driver’s side tail lamp assembly to access the ground for the fuel pump. Remove the screw holding the black ground wire. Scrape the paint from the body and corrosion from the wire terminal. Add a 10 gauge wire, with an eyelet on each end, from that grounding point to a bolt on the frame. Better yet, on both Cherokees and Comanches, complete Tip 29 for the best fuel pump grounding. Be sure to scrape all mounting points to bare metal and apply also.https://i1.wp.com/cruiser54.com/wp-content/uploads/2015/10/Fuel-Pump-Ground-Comanche.jpg
If you want to upgrade your ground and battery cables with custom made parts, contact Neal at www.meanlemons.com
Revised 02/04/2017
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
cruiser54
SKIP TO CONTENTTRANSMISSION CONNECTOR REFRESHING
Over near the transmission dipstick tube are 2 rather large connectors. One is black and goes to the NSS and the gray connector goes to the transmission itself
. These 2 connectors carry all the info between TPS, TCU, NSS, speed sensor, and transmission solenoids.
Unplug each one, visually inspect for corrosion or bent pins, spray them out with electrical contact cleaner and plug them back in.
Additionally, if your Jeep is an ’87 to ’90 Renix, it’s always a good idea to reach up under the glovebox area and unplug the connector to the TCU and spray it out along with the receptacle of the TCU. While you’re there, find the fuse right in that area for the TCU. Remove it and spray out it’s receptacle and clean any corrosion from the fuse.
Junior Member
Joined: Jan 2019
Posts: 82
Likes: 2
Model: Cherokee (XJ)
Tips 1-5
As a note of recommendation. On our 1989 XJ that I am cleaning up with my 16 year we just performed tips 1-5 from Cruiser54. We had an intermittent stalling issue while driving and giving it lots of gas. Before throwing parts at it I decided to do 1-5. That problem is gone as well another problem.... It starts easier. To be honest it just runs better.
Anytime we are working on the Jeep now my son will ask what Uncle Cruiser has to say on the topic.
Anytime we are working on the Jeep now my son will ask what Uncle Cruiser has to say on the topic.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
As a note of recommendation. On our 1989 XJ that I am cleaning up with my 16 year we just performed tips 1-5 from Cruiser54. We had an intermittent stalling issue while driving and giving it lots of gas. Before throwing parts at it I decided to do 1-5. That problem is gone as well another problem.... It starts easier. To be honest it just runs better.
Anytime we are working on the Jeep now my son will ask what Uncle Cruiser has to say on the topic.
Anytime we are working on the Jeep now my son will ask what Uncle Cruiser has to say on the topic.
Too funny!!
That makes my day!!! Father and son projects are the best. Mine was a 52 ford pickup with a bad flathead V8 we bought for $75.
I was 15 at the time. we towed it home with a chain. I had no driver's license.
We scored the last Flathead v8 rebuilt from the Montgomery Ward's catalog and installed it together.
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CF Veteran
Joined: May 2012
Posts: 7,965
Likes: 964
From: Lost in the wilds of Virginia
Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
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