Intermittent Overdirve

[fyrfytr1717]

After 15 years of almost trouble free operation, my '99 XJ is finally starting to have some issues. I think I'm already headed in the right direction on this one, but just wanted to make sure as I seem to have some (but not all) of the symptoms of a bad NSS.

When I headed to work the other morning, my Jeep started and ran fine. However, I noticed that it would not shift beyond 3rd gear. It was holding steady at over 3000 rpms at 65mph. When at speed (65mph or so) I could shift back and forth between D and 3 and there was no change in RPM's. The TC seemed to be locking up just fine, just no 4th gear for some reason. It stayed like this throughout my entire 30 mile drive.

A couple mornings later when I returned home from work, it shifted into 4th just fine. A handful of short trips I took the next few days were unremarkable as well. I figured my gremlin had come and gone. On my next drive to work however, it was back. Same thing with no change in RPM when moving the gear selector back and forth between 3 and D. This time, at about the halfway point in my commute, I stopped and shut down the engine. Fired it back up and it shifted normally into 4th the rest of the way into work.

So, I'm thinking this is somehow temperature related. We've (finally) gotten cold here in central California with AM temps in the mid 30's. Could it be that the grease in my NSS is extra gummy when cold and that it's loosening up once the engine gets warm? Additionally... my check engine light is on and I can't seem to clear it, I had to replace fuse #10 in my passenger side kick panel a few days ago, and I found out last night that my reverse lights aren't working. No issues starting at all though. Code reader is bringing up P0700 (Trans Control Sys), P0705 (Trans Range Sensor), P1491 (Radiator Fan), P0443 (Evap Emission System Purge Valve), and P0645 (A/C Clutch Relay) right now as well. I think a few of the codes may be from a loose connection in my radiator fan override switch and are unrelated, but I figured I'd mention everything in case it helps.

Comments, suggestions? Am I on the right track? I'm planning on servicing my NSS tonight. Is there something else I should look at?

 

[98NWCherokee]

I think you're on the right track with your codes and symptoms, especially the loss of reverse lights. I've had my 98 XJ for 5+ years now and I've had to rebuild the NSS once, and adjust it twice. The rebuild/clean procedure found here on NAXJA is very thorough and walks you through the procedure. The torque values for the NSS are very very low.....like In/lbs. so mine backed off after about 4 years and had to be re-adjusted and tightened again last year. I think this will address your P0700 and P0705 DTCs and may address your TC lockup issue as well. I had problems with my TC lockup and eventually had to replace the lockup solenoid in the transmission. I ended up replacing all 3 solenoids ($65 for all 3) and haven't had a problem for over a year. I was getting P0743 though which is not in your list of DTCs.

Good luck and it sounds like you're on the right track.

 

[fyrfytr1717]

Serviced my NSS last night. That's a good New Year's Eve activity, right? So my reverse lights are working again and I was able to clear all the codes. I found my #10 fuse had blown again and I was also able to trouble shoot my radiator fan circuit and determine that there was in fact a loose connection in the wiring for my override switch. We'll see how overdrive does the next couple of days before I call this repair a complete success.

 

[fyrfytr1717]

Seems this issue was fixed by rebuilding the NSS as it has been shifting properly ever since. The only variable remaining is that we have not had sub-freezing temperatures all month thanks to this nasty thick fog we've been dealing with. If the problem is in fact temperature related, it is looking like it may be next winter before I can confirm it one way or the other...

 

[ehall]

Sounds like your trans fuse is blown, its the fuse for reverse lights and the TCU.

Don't know where it is on your 99. Some have it in the PDC, some have it in the cab, some have both.