Hello!
I am seeking some input from you guys regarding a problem with my XJ12 TH400 transmission.
I need to mention first that the car hadn´t been driving since about 2002/2003 when I bought about one and a half year ago.
I fixed all the issues regarding the engine and it´s super smooth now.

However, on the first test drive it was obvious that the transmission was stuck in 2. gear. I have reverse as well.

I have done a quick check to see that the vacuum line is open and works correct - it does.

Other than that, checking the fluid and inspecting the shifter cable I have not gone into the issue much further.
It is worth noting that I hear no whistling noise from the vacuum modulator nor do I detect any white smoke from the exhaust.

Any pointers before I start taking it all apart?

 

The issues I have had with teh TH400 are:

The nylon gear on the Governor, located under the tin plate on the RH side of the extension housing. They strip from A) Stale fluid, B) Water contamination is said fluid, C) Old age. This item has prime affect on the gearchanges, such as what you have. It will go forward and backwards, but not change gears.

The o/ring on the top of the suction tube for the internal filter split, age related mainly, and the pump will suck air and not build sufficient pressure to change gears via the Gov.

Never had any real issues with teh Select cable.

 

Thank you very much for valuable input.
I will check into this.
Do you know if the parts are available as a kit for example?

I’m a BMW master technician and know «everything» about them, but Jaguars are new to me. Need to build up both knowledge and acquaintances in this department

 

I had the same experience you are having Henrik. 1976 Oldsmobile 98 Regency with 6.6L engine. Bought it new and with less than 20K miles, one day it would not shift beyond 2nd gear. Exactly as Grant outlined, the nylon governor gear stripped and that was caused by one of the pins holding one of the "fly weights" had backed out far enough to dig into the housing and seize the governor shaft, hence the shaved gear. Those pins (on mine) had a head on one end, but were just pinched flat on the other, sometimes not enough to keep them from flying out of position.

Dave

 

I don't know about availability in Europe, but in North America the Turbo-Hydramatic 400 was very, very common in GM cars and trucks, and all of the internal parts are commonly available. If you can't find a repair kit locally, or it's very expensive, there are many available online from the US or Canada.

 

TH 400 bits are easily available in the UK, anyway.