Hello guys. In need of advice once again.. I'm having a problem out of my 95 xj6 (300). It started out as a bad oil leak from what seemed to be the rear main seal. Consequently I found a shop that said they could do it for a reasonable price. At the time I didn't have the tools or whereabouts to do it myself (Wish I had)..
Long story short, the leak came back not to long after getting the car back. On top of that now there's a new problem with the transmission jerking into its first shift in gears. It's holding to about 3000rpms and then violently jumping into the next gear. At this point the trans light comes on. It seems not to be shifting all the way out from there. On top of that when pulling off from a dead stop I can tell that the trans has not shifted back down to pull off in first gear. It seems like maybe its in second or third. I'm really leaning towards third. Only after the ignition has been turned off and crank again will the trans light be off and car pulls off in first gear again. And starting the same symptoms all over again. Is there any specific part, relay, ect. that I can try to look into as a fix. I swapped trans ecu and problems remain..

 

Throwing darts blindly here...perhaps its a software issue. How about disconnecting the battery for 30 min, reconnect and take her for a drive to 'relearn' the shifting of the gears?

 

Yeah I'm trying to get this figured out before giving up and finding another trans somewhere and still ending up with the same issue because it could be something other than the trans itself causing this

 

Same behavior in Sport and normal modes? I'm assuming you have dropped the pan, had a look at the accumulated residue, and renewed the fluid?

 

Yes it's acting the same in both modes.. And I have dropped the pan, changed filter and fluid.. Wondering if there is a plug or something that might've been left off or damaged that I should look for..

 

Hi goodgame,

Given your description I assume that prior to the work to replace the rear main oil seal the transmission was operating properly with no signs of any problems? It does seem possible that something was not properly reconnected during reassembly, or since the reassembly a connector has been contaminated with oil or transmission fluid.

The transmission in your car is probably the same ZF 4HP24 as in our '93 XJ40. There are a few things you can check. You asked about any plugs, and there is a large electrical connector on the gearbox that can be loose or contaminated with oil. See the photos at this link:

ZF 4HP24 Electrical Connector

You can also check the cable that connects the gear selector lever with the rotary switch on the left side of the gearbox, and open the rotary switch to check for any signs of oil contamination or bad solder joints:

ZF 4HP24 Rotary Switch

I can't recall whether the X300 uses the same decoder module but just in case here are the photos of the one in our late XJ40:

ZF 4HP24 Decoder Module

In case it might be helpful, there's an excellent diagnostic procedure for the 4HP24 in the late XJ40s in the Jag-Lovers eBook that may be similar for the X300:

ZF 4HP24 Diagnostic Procedure

A couple of other random thoughts: on our '93 the most common cause of transmission Limp Home Mode has been oil contamination of the electrical connector for the throttle position sensor/potentiometer (TPS), so that would be worth checking. Also, the MAFS provides the engine load/torque signal the ECM and TCM need to orchestrate smooth gear shifts, so it would be worth cleaning the MAFS hot wire and electrical connector just to rule out contamination as a contributor to the gearbox issues.

Cheers,

Don

 

Ok thanx, I'll look into all you have provided.. Fingers crossed