Hi all, my 1980 Pre HE 5.3 V12 Jaguar XJS Auto has just gone through a nut and bolt restoration, I need help and guidance with a Speedo related issue, It has stopped working, I have removed the clocks and the insturment cluster is fine, I have checked the cable drive from the gearbox and the cable is fine, leaving me with the concern that the speedo drive located in the end of the gearbox is now broken, how can I check out this element please, and if it is due to the drive failure, how do I remove the broken one, will I loose the Auto fluid etc, and where do I get a replacement from, and what specifically am I asking for,

I look fowards to any help you can offer,

Thanks

Sayers

 

Welcome to the forums Neil,

I've copied your Intro questioh here for advice from members with the same model.

Graham

 

Inside the gearbox (I am assuming it is a GM400 by 1980) is a plastic toothed gearwheel which drives the speedo cable. If you undo the bolts or whatever holding the horseshoe shaped clip holding the casting onto the side of the gearbox the cable drive comes out of, you can withdraw it and then the toothed gearwheel. No fluid will come out. If you test the cable from the gearbox end with an electric drill to see if the speedo does indeed move, then it is highly likely one of these things is causing the problem: Gearwheel teeth chewed up; or the square drive on the end of the gearwheel rounded off; or the right-angled unit that the gearwheel drives has rounded off female drives, or the cable itself at the gearbox end has a rounded off square drive.

 

Thankyou very much,

 

If the drive gear is duff, where do I go to Purchase another one (second hand or new), Thoughts ??

 

It is common parts for a GM TH400. I think you can find it on Amazon.

 

Do I definitley have a GM TH 400, ? not a Borg Warner 3 speed box ?

 

The TH400 was fitted from '77. So that's what you have unless someone has changed it, but they probably haven't.

 

Ensure you count the teeth on the old one carefully, you must have the same number. The parts are colour coded, so if you remove a (say) brown one, in theory a new brown one will have the same number of teeth.

 

This was the correct one for my 87.

 

Thankyou for all of your help