I just sourced a replacement Moss box with OD for my 1960 MK2. Current box is tired but original to the car. Car was originally a 2.4, but now with a 3.8. Rear axle is 3.77:1

Shifting is still a crap shoot at times, even after al the external linkage bushings have been replaced. Also I was advised that the OD internals (weaker springs?) may be different for 2.4 than for a 3.4 or 3.8. Thus the decison to source a replacement unit.

As luck would have it the replacement is a close ratio box. It is stamped on the side of the cast iron housing GBN12564CR. The top AL housing is stamped GBN31706JS, so it is not the original top housing. Current box is GBN33557JS.
Also as luck would have it, the internals of the box, the gears, sliders etc. look as new. No sign of any wear or use. So it must have been rebuild years ago and never installed. Not sure on the internals for the OD but was told the entire unit was unbolted from a 3.4 engine.

I measured the ratios of each of the gears by tuning the input and measuring the output rotations, and as close as I can measure they match the numbers in this table for a CR box.

Gear Ratios 1st, 2nd, 3rd, top:
Double helical gears - 3.95, 2.43, 1.45, 1
Suffix O or no suffix letters - 3.375, 1.982, 1.367, 1
Suffix CR, MS or J - 2.980, 1.740, 1.210, 1
Suffix JS - 3.378, 1.860, 1.283, 1
First and reverse are always equal.

Later this year when pull drivetrain for engine rebuilds, we will swap the boxes.

So the question is, with living in Florida, no steep hills, will the taller 2.980 first gear be sufficient for starts as opposed to the the shorter stock 3.375 in the car now?

Anyone have a CR box in their MK2?

I think this may be a perfect ratio box for the car..

Thanks
jjsandsms

 

Not sure if this helps but I live in a flat Country (Netherlands) and I really hardly ever need first gear. I still use it because I love the whine but I can easily pull away in second.

 

Interesting as if you have a standard moss gearbox then second gear ratio is 1.860 whereas the close ratio box I now have first gear is 2.980, so I would expect no real issues.

Thanks
jjsandsms

 

I have a standard moss box

 

I think that the driver's handbook that came with Mk2 cars says that it's acceptable to start in second on level ground. I don't see a problem with the close ratio first gear. In fact, I bought a close ratio (all synch) gearbox for my car. Possibly, if you fitted a lightweight flywheel and a 3.08 axle, you would need care with hill starts, otherwise, don't worry and enjoy having a more useful first gear (even if it screams a bit).

For the change quality, the basic synchromesh of the Moss box doesn't help, but, in some cases, the change can be improved by grinding some rough corners off where the selector finger slides into the slots in the striker rods. It's accessible via the small lid on top of the box.

 

The attached pdf gives the ratios of the all sync gearboxes. The standard 1st gear ratio is 3.04, not very different from the Moss CR. And the all sync CR is 2.68, quite a bit higher than the Moss CR.

My guess is the lower ratios of the Moss 1st might be to help engagement from rest. However, the trick is to use the 2nd gear cones to help the box into first. Move the stick towards 2nd and then forward into 1st.

 

i've made it a habit to always use 2nd gear to prepare for a move to 1st OR reverse. otherwise i'll get a some grinding. and even then i might get a touch of it. i've owned a number of 50's and 60's manuals both American and British and it seems to be the nature of the beasts.

to be honest, my 2007 Aston Vantage will grind going into second until the transmission oil warms up a bit.

 

[QUOTE=Peter3442;2837221]The attached pdf gives the ratios of the all sync gearboxes. The standard 1st gear ratio is 3.04, not very different from the Moss CR. And the all sync CR is 2.68, quite a bit higher than the Moss CR.

My guess is the lower ratios of the Moss 1st might be to help engagement from rest. However, the trick is to use the 2nd gear cones to help the box into first. Move the stick towards 2nd and then forward into 1st.[/QUOT

Thanks for the data on the all sync boxes. With the all sync box close ratio, the 2.68 is quite a bit taller than the CR moss bos which I just got with 1st being 2.98. I would think even on a normal slope it might be tough getting going. But one going one surely must be able to really wind it out! Of course much of this talk depends on the rear axle ratio.

I am very anxious to get this new box in the car later this year.

Thanks
jjsandsms

 

The 420 manual without o/d had a 3.33 axle, giving an overall 1st gear ratio just over 10 (with non CR box), which seems to be typical of medium to heavy cars with reasonable performance.

We should keep in mind that the lowest ratio is chosen to allow hill starts with a loaded car and a trailer. Our cars pre-date most gross train weight rules, but, if we assume 250 kg of load in the car and a 1,000 kg trailer, we're 75% over the kerb weight. I don't think many of us are going to use our precious Mk2s to drag trailers. So I'll guess that the 2.68 1st gear should be OK with a 3.77 or 3.54 axle. Of course, it may be a bit more difficult to spin the rear wheels in the traffic lights grand prix!

 

Thought I would share a photo of the close ratio Moss box recently purchased. The inside shows how pristine this box is, as if it was never used or was rebuilt many many years ago.

We will still go through it in the next few months before going in the car.

jjsandsms