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Hi everyone. I am restoring my 88 XJS couple and have a leak at the speedometer drive output on my 1988 XJS TH400 auto. It is currently my last leak. I say currently whilst touching wood. My car does not have the cable per se as it is electric and not cable driven. The gearbox is not the original and the output has been blanked off as such. Just wondering if it is possible to remove and replace the seals insitu. There is little room between the box and the trans tunnel and if the speedo drive is still in there (which I think it would be to maintain the seal) would there be enough room to remove, replace seals and refit. Hopefully someone has done this before. Cheers
If the speedo drive unit is only a simple blanking plate, then the leak is the gasket under it. The other parts on the earlier system are not there, as the speedo pick up is in the end cover plate of the diff unit.
Not sure of what you mean by the TH400 not being the original. I understand the box may have been replaced, so no longer the one the car came with, but a Jag V12 TH400 in unigue to Jaguar. The internals are "mostly" the same as the GMH stuff, but the casing is Jaguar specific.
Remove that plate, you will NOT get flooded, and clean the area thoroughly with solvent. Apple some Hi-Temp RTV to a gasket, cut one from gasket paper if need be, and reseal the thing.
Grant. Thanks for your reply. Photo of the issue here. I'm starting to think when the trans was fixed/replaced they got an older one (ie pre diff cable) with the speedo drive still in and simply just removed the screw on cable. So rather than just a blanking plate I think it is the whole housing that has 2 x o-rings in it. If it does still have the gear drive and shaft I don't think there would be enough room to remove it with the gear box in place. Anyway, ultimately, I guess there is only one way to find out.
There are two seals, yes. Adapter-to-case and gear-to-adapter. Should be easy find if you just Google "TH400 speedo seals" or similar. I think there would be enough room to wriggle it out....but am not sure.
You must have a later 88 with the diff mounted speed sensor. Earlier cars had a speedo transducer attached to that adapter....just in the same fashion that an old fashioned speedo cable would attach. The change was at VIN 142xxx or something like that.
Doug. Thanks for the info on the blanking plate. What a great idea. Didn't think to google that. I'll get it out first and check the o-rings. Pretty sure they would be generic so should be easy fix. Just wanted to see if I could actually get it out if the gear shaft is still in there. Cheers Lachy
FYI the end result of this little problem. Got the speedo drive out. Very small space to get to but came out fine. No trans fluid seepage on removal. I ended up removing the plastic speedo gear altogether, and got the internal hole aluminium plug welded, and sealed the external hole with silicon sealant just so no road grime gets in there, put on a new main seal o-ring (the large external o-ring) and back in with no leaks now. Cheers to Grant and Doug for the input.
XJS TH400 Speedometer Seals
