1990 XJ40 gearbox fault

[tinyspanner]

Hi

I have a 1990 XJ40 4.0 Soverign Auto which is stuck in 3rd gear. Has anyone heard of this before & any advice as to how to fix.

Thanks

Angela

[GavinPearson]

It's an electrical fault, nothing unusual, but the gearbox has defaulted to the 1:1 ratio.

You will need to visit a dealer to find out what the electrical fault is.

Please note - if the specialist tells you that you need a new gearbox then they are wrong. You don't. The only fault the gearbox might have is electrical within the solenoid body or a sensor, but even that is repairable without a transmission change.

[pwig]

Wow it has 3 electrical faults?

[tinyspanner]

Thanks Gavin

That sounds quite promising. Once it has gone into this 1:1 mode you mention, would it need a dealer to reset the computer after it is repaired or could I just bring it home and replace the faulty part when it had been identified?

Thanks

Angela

[GavinPearson]

The transmission needs a dealer to look at it to pull the diagnostic trouble codes from the Transmission Control Module (TCM).

If you disconnect the battery for 15 minutes and then reconnect everything the transmission will be able to operate normally in drive. What normally happens is that the TCM detects a fault such as excessive slip from the clutch plates and then defaults the trans to 3rd. However, it is fairly unlikely that this happened if the trans was working OK before it defaulted, and in any case, the dealer needs to diagnose the trouble.

I have seen a lot of transmissions default because of electrical problems, and in particular, issues with the harness, so I would get it properly diagnosed and not resort to throwing parts at it - effective, but crude and extremely expensive.

It may turn out that the transmission is showing signs of wear, however in most cases they can have a change of oil and filter and be significantly rejuvinated.