Mark V second gear issues

Pre-XK
1

Hi All,

Just having a little issue with the second gear disengaging when I decelerate in that gear, any hints as to the possible cause and remedy?
Thanks

Grant

2

Among possiblities.The spiggot bearing in the back of the crank, wearing the inside of the crank and not supporting the end of the shaft
And then there’s …

3

It may be worn second synchro sleeve, the beginnings of the “stuck in first” syndrome.
http://www.jag-lovers.org/xk-lovers/library/gearbox_reilly/gearbox_reilly.html

4

Thanks Rob,

I have not had any experience of sticking in first(yet)
I will take the top off the box and have a bit of a look to see if anything is obvious, probably just wear on a 70 year old? I have a spare box and will have a look into that first to get familiar with the workings of same.

Cheers

Grant

5

What oil are you running in it?

6

Note sure about the original oil that was in from the PO but I have topped up with penrite 20W60 which is a substitute (their claim) for SAE 30.

7

Unless Penrite is using some classification other than SAE viscosities, 20W60 can’t be right.
In the SAE system, 20W is the Winter or cold viscosity, and 60 is the warm viscosity, which would be way too viscous for gear shifting.
If you were in the US I would say to use SAE30 non-detergent air compressor oil if you can find it, or SAE10W30 or 5W30 motor oil as I don’t see how the detergents can hurt anything in there.
I don’t know the viscosity spec situation where you are, but Ed will no doubt have some good advice.

8

Rob is (as usual) 100% correct.
A ‘Moss’ gearbox, and also the Jaguar made ones under license to ‘Moss’ (the gearbox number prefix tells you whether Moss made or Jaguar made), should use a straight single grade SAE30 non-detergent gearbox oil, and under no circumstances use any more modern oil with friction modifying additives, as is usually included in all Engine oils. Indeed I doubt you can buy a gearbox oil with detergents included, but if so, I cant see that that would matter, as does friction modifiers.

Now PENRITE - local Australian Oil Company - does offer the correct SAE30 GEARBOX OIL.
If you local stockist does have it, contact Penrite direct.

Roger

9

Please be aware that SAE engine oils and gear oils have different viscosity ratings numbers. Engine oil SAE 30 is about the same as Gear oil SAE 85. I put engine oil SAE 30 in my Mark V transmission. An SAE 60 engine oil is about twice as viscous as SAE 30 engine oil.

Having said this suggestion that your tranny oil may be too thick, I can’t really say why that might lead to popping out of 2nd when decelerating in gear. But I would change the oil to the right grade and see if it helps as an easy step.