Transmission Mount Springs 4.0 Auto

[mwsmith29]

On fast acceleration my cooling fan catches on its surround indicating I have a problem with the engine / gearbox mountings that are allowing excess engine lift.
I have changed the front engine mounts which were in need of replacement but the problem still remains.
The gear box foam buffer has also been changed so I expect one or both of the gearbox mounting springs have deteriorated or maybe its the bobbin type mounts on the side of the engine.
Before I start buying new parts I just wondered if anyone knows what length the unloaded springs should be so I can check them.
Thank you,
Martin

[ptjs1]

Martin,

I don't know the spring length but your symptoms are really indicative of a worn gearbox mount.

Take it really easy until you've fixed it. If the fan lets go, it easily punch a hole through the bonnet and make a real mess! You don't want that happening.

Good luck

Paul

[mwsmith29]

Hi Paul.
Thank you for the advice. I will order new springs and update here once fitted.

[ptjs1]

The other part of the mount that deteriorates is the bush which is made of some material that softens and ultimately disintegrates. See if you can source and replace that at the same time.

Cheers

Paul

[mwsmith29]

Yes it’s made of a hard foam material.
I replaced that a few years ago. It’s still in perfect condition.

[mwsmith29]

I purchased the longer spring CBC4745 as this looks the weaker of the two springs but was disappointed to find it was ever so slightly shorter than the original one I had taken out.

My friend gave me the springs from his low mileage Celebration Convertible that he had recently changed on advice from an ex Jaguar mechanic when his foam buffer needed replacing .
I have fitted these even though they seemed to match my old ones in both length and perceived stiffness.

They have done the trick ! The fan holds its clearance even when I floor the accelerator and the car smooths out the many speed bumps that I encounter on the roads much better.

It just goes to prove how finely tuned these cars are. I will eventually fit a brand new set of springs but for now all is well and another problem solved and in time for my trip to the Bicester Jaguar Festival.

Thank you ptjs1 for your advice.

[ptjs1]

Martin,

Well done!

It just goes to highlight both:

- how sensitive the whole setup is to the integrity of the various components
- that one can't really judge the true effectiveness of those springs just by free length and subjective assessment of their compression

Do let us know when you source and fit new springs!

Cheers

Paul

[ng4xjs]

My gearbox mount is merrily clunking around on harsh acceleration/de-acceleration (so not very often then). Did change the diff oil today as not been done for 5 years, at least I see that only the inner spring is currently available along with the foam bushes but although job really needs doing seems pointless doing it twice, unless of course the spring is good.

On a slightly different note none Jag track rod ends I put on about 4 years ago are now marginal and could probably benefit from being replaced before next MOT (Jan 2021). Apart from that, oh and no fuel all working welish.

Nick