Thread: 2a Gearbox number

The number on an SII/SIIa is usually on the LHS of the selector cover, but many boxes don't have any numbers, having been lost when cases or tops being replaces etc.

The number is stamped in and the sequence should be similar to the RHD home model of the vehicle it's mounted in.

When Army gearbox repairs are necessary in-service, boxes are usually replaced with exchange units and the original sent off for factory or base re-build.

Diana

Hi
The lettering painted on the gearbox did say the word SERVICE and something else I think, but it was coverd in muck. It is a shame it washed off, when I cleaned the case. So it must be a replacement gearbox. Is there anyway to tell if it is Suffix B C or whatever.

Regards
Mike

Hi Mike

Externally it is only possible to identify some aspects and remember it is possible to convert a suffix B into a suffix D merely by replacing the layshaft.

IIRC in the absence of numbers the SI, SII and SIIa "A" suffix boxes can be identified by the dip stick or the recess in the selector top (LHS) for the dip stick. By the later suffix SIIa boxes the recess is absent.

Essentially the big differences from Suff A are the big layshaft front bearing (suff B ) and the shoulder for 2nd layshaft gear instead of the circlip. The only other major differences are the sealed primary pinion/throwout at IIRC suffix G-H.

Diana

Didn't the gear ratios change slightly at some point?

John

Originally Posted by JDNSW

Didn't the gear ratios change slightly at some point?

John

yes, but the thing that made the D suffix so much more reliable was the bigger layshaft bearing (suffix B ) and the shouldered layshaft the rest was just tweeking.

Suffix: A/B -- C on
1st - 2.996 - 3.6
2nd - 2.043 - 2.22
3rd - 1.377 - 1.5
4th - 1.000 - 1.00
Rev - 2.547 - 3.02