Gearbox noise after changing gearbox oil + filter ?!? XJS-V12 auto'83
 

I'm in shock.... I drove my Jag to mechanic: I wanted new gearbox rear mounting spring + new gearbox oil + filter. Now after the first kilometer a big shock. The gearbox is loud, especially when it is shifted to 1st gear. Previously, he was working almost totaly silent. Now is also new noise from driveshaft, but I understand that it's probably a different position because of the new spring ... But what's wrong with the gearbox ????

Habe you checked the fluid level? A louder transmission is sometimes a sign of a low fluid level.

They have put the rear mount back incorrectly and the driveshaft is most probably touching the rear of the two fixing brackets that holt the rear mounting. 1 in the diagram:
https://www.jaguarclassicparts.com/i...ges/mb5735.png

Here you go, that complaint is common when things are done wrong.

As said, LOW fluid is a certain contender here for some noise.

Ufff ok... nothing wrong with gearbox, just wrongly made up. But is this spring for all models the same? The mechanic said that the new spring is longer than the old one, is this the reason for wrong position and this strong noise. Is possible?

The spring for the V12 TH400 transmission is specific for that application, as is the spring for the 6cyl cars with the Borg Warner transmission. They are NOT the same spring at all.

The new spring may be longer than the old spring, due to the old collapsing from age etc, although that is a rare thing.

I still think he knows not what he is doing.

Reassembling that mount CORRECTLY, and aligning that central pin CORRECTLY will be the first thing needed.

Check the trans fluid level, HOT, and engine running at idle. A little OVER full it better than under full in MY opinion.

He give me spring with ID number: CCC5763. Is this for may Jag 5.3 H.E. - V12 1983 ?

According to my parts listings:

CCC5763 is the LATE XJS, and XJ40, with teh 6ltr engine and a different transmission, as in 4 speed electronic, versus your 3 speed non-electronic.

Same listings have your as:

CAC23271 (old part number), going to CAC6759,as the correct part number.

I seriously doubt they are the same, or Jaguar would have combined ALL teh springs as ONE part number.

Differences, NO IDEA, but in MY opinion, the wrong spring is installed.

Widely available from the specialist suppliers. eg
Part search results from David Manners Ltd - CCC6759

Goodo,

Simple cars, only made complicated by "fiddlers", and thats my polite words to save the Ban Stick from Graham.