JAG XJS AUTO GEARBOX PROBLEM

Honest John Back Room » The Back Room Archive
What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks
View Threaded
Tue 15 Jan 2002 21:29
JAG XJS AUTO GEARBOX PROBLEM - HEXED
GOT A 93 XJS WITH 31,00O MILES ON THE CLOCK.
PROBLEM IS WHEN I SET OFF IN THE MORNING GEARS CHANGE UP 1ST, 2ND, 3RD, OK - THEN IT GOES TO 2ND AND RARELY GOES UP AGAIN, 5 MILES TO WORK, PARK UP.
AFTERNOON START UP DRIVES PERFECT THRU THE GEARS NO PROBLEMS.
ANY IDEAS?
GEARBOX OIL IS CLEAR AS A CLEAR THING, FILTERS PERFECT.
ANY HELP MOST APPRECIATED.
CHEERS
HEXED N SKINT
Reply | Report as offensive | Link
Wed 16 Jan 2002 09:06
Re: JAG XJS AUTO GEARBOX PROBLEM - David Withers
Here are some thoughts to start off with ...

A common cause of delayed or non-existent gear changes is a low fluid level. It is vital, with most boxes, to check the level with the engine running and preferably with the oil at normal operating temperature. With the engine switched off, a lot of the fluid drains into the sump and gives a falsely high reading. When the pump starts working, this draws up fluid into the upper part of the box and the level in the sump drops too low and starves the system.

The fact that the filter is clean does not entirely eliminate the possibility of dirt or swarf in the system stopping a valve from seating. The dirt could already be in the box and have got dislodged, or it could have been introduced via the fluid cooler, in which cases it could have reached the valve block before going through the filter. For example, if the cooler is situated in the radiator and a radiator repair has been carried out, a blob of solder could have found its way into the box and bypassed the filter. The filter would normally act only on the fluid being picked up from the sump.

The fluid being clean is a good sign that it hasn't overheated and that the brake bands haven't disintegrated. A heavily worn brake band can be another cause of poor changes. This shouldn't happen at only 31000 miles though!

The fact that your gearbox works OK when you use it for a journey later in the day baffles me. All I can think of is that it has something to do with the fluid being warmer and dropping in viscosity. I wonder if the problem is simply a sticking valve that works OK once the fluid has been warmed but sticks overnight when the fluid cools? The low mileage might give a clue here as valve sticking sometimes occurs when a vehicle has stood for a few months. This can often be cured by driving the car quite severely for three or four miles with lots of forced changes up and down the box -- might be worth a try.

Hope there is something here to help.
Reply | Report as offensive | Link