I recently purchased a ‘95 XJS V12 that has an odd transmission quirk: gears won’t shift between second and third until the engine is warmed up or you shut off and then restart the engine. The seller thinks it’s something electronic in the transmission.

Any thoughts?

 

twojags1992,

Is it just not changing out of 2nd when it starts off from rest in 2nd.? What happens if you make the car start off in 1st gear? Does it then change up into 2nd and then get stuck? Or will it then go from 1st to 2nd to 3rd then 4th?

Paul

 

I'm not sure if this applies to the 4L80E transmissions Jaguar used but the early versions of this transmission used in GM trucks had a similar issue. The seal rings feeding the direct clutch (3rd gear) were a solid teflon? ring and they would shrink over time and they wouldn't shift 2-3 until they warmed up. The later units used a different material that eliminated the issue.

 

As far as I know, the internals of the 4L80e were identical to the GM units with the exception of the wiring for the solenoids and external connector. The Jaguar version starts in second as the default unless in sport mode, GM starts in first.

Thus if you use a GM internal harness for the solenoid wiring it will be backwards to the way the Jaguar version operates.

 

Good to know. 1'm a semi retired transmission tech and have rebuilt a few Jag M12 and TH400 units but never had the opportunity to do a Jag 4L80E.