I had an o/d and gearbox from a S1 XJ6 in my first car (E 2+2 4.2 1966) for over 16 years. I used EP90 (Mobil 75W90 or similar) in it and never had an issue. 67.000 happy kms.
I have one in my 1975 XJ6C from the factory and it has been rebuilt twice. Nothing to do with oil, after perhaps 100.000 or 200.000 kms it started slipping. After that I bent the oil pump plunger while installing it back. Then electrical problems (created by a previous workshop) lead to the catastrophic failure and while it was rebuilt (and I rebuilt the original gearbox as the mainshaft needed to be replaced) I had another gearbox with o/d from another S1 XJ6 that I drove for 5.000kms.
That whole assembly with bellhousing is now available, I think I will post a classified in the near future.
None of those o/d’s ever made a loud clang when engaged or disengaged. They engage very smoothly and revs drop 20%.
The only slightly loud or clunky engaging and especially clunky disengaging I ever experienced was a 1967 Volvo 1800S. But that’s a different Laycock De Normanville overdrive and it may have had a couple of hundred thousand miles on it.
If an XJ6 o/d is clunky, there has to be something wrong with it.
Cheers!
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
22
So it calls for some additive that engine oil lacks? Makes sense.
Are all the gears in that Moss box straight cut? That must be noisy.
Correct. Factory specification for a Moss is SAE 30 and I run this with success. I use the same Penrite oil as you do in my Mk2 steering box, good as well. Paul.
Nope, just first and reverse. The rest are helical. Yes, straight cut gears are always noisy!
Back in the days Jaguar used SH prefix for ”single helical” in gearbox numbers, I think it was superseeded by ”JH” but I can’t remember what prefix was for early double helical gears.
Same in nearly every motorcycle since the mid 1960s - spur gears and engine oil.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
28
Back around 1985, we had sold our house in S FL and were preparing to move to the Tallahassee area when the transmission failed in our 1973 Triumph GT6 MkIII. Easy to come out, easy to disassemble, but I needed parts to fix it and I needed them in a hurry. A roller bearing in the layshaft had failed, screwing up the gear cluster. There was a guy I knew who had all sorts of Triumph stuff laying around so I gave him a call. He said yeah, he can help me. When I get there I find out that he’s got a GT6 transmission in pieces scattered in the dirt behind the shed. For a few bucks I can take the whole thing. I thought I only needed one part, but WTH, took every piece I could find just in case.
So I’m trying to put the gearbox back together with a different layshaft, and it won’t go into the box. Something ain’t right. Come to find out that some of the helical-cut gears are a different helical cut than the gears I had. Like, the teeth are at a different angle. So they won’t mesh at all, at least not unless the shafts are not parallel. So I had to backtrack a bit and use basically all of the gears I had gotten out of the dirt from behind that shed.
Cobbled that thing back together, complete with a couple of ball bearings that fit quite loosely in the housing and at least one C-clip that was dished from stress. I needed a new bronze thrust washer, no time for such stuff, just cut a piece of brass from brass stock. The GT6 has a fiberglass tunnel that is removed from inside the car to access the tranny, and I was so pressed for time I didn’t even put that thing back in. I just set it on the back shelf and drove the car 8 hours with a gaping opening in the floor to get it to Tallahassee. I think I tossed a bunch of tranny parts in the trash.
