Thread: Gearboxes RRC 12CxxxxxC and 355xxxxxC

Originally Posted by VMKrister

Dear friends,

I have a RRC 1982 prototype with a 5-cyl VM diesel - the only remaining.

The gearbox in the vehicle is 12C05312C and it has no 2nd gear...
I have found a gearbox 35503643C, new in box from factory, but the transfer case is empty...
Dave Ashcroft has verified that the two are LT95 gearboxes.

The 12 C has a ratio 0.9962 in high range.
I have not found out the ratio of the 355.

How interchangeable are the inmates from these two boxes and what in the boxes determine the output ratio? Main box or transfer box??

Who has spares for these boxes, Ashcroft does not have, and who could take on and fix a box?

I have seen on this fora that some of you have a lot of knowledge re. these gearboxes! Consequently I have great faith in getting some help!

Krister in Uppsala Sweden

G'day Krister and welcome, The 2nd gear from the 355 box is identical to the 12C. In the actual gearbox the only changes between the two is the early 355 boxes had a stepped reverse idler shaft and wide gate or long throw selectors, later ones and the 12C,13C,14C models had the stronger unstepped reverse shaft and narrow gate or short throw selectors. The transfer box ratio is what determines the output ratio. There are quite a few ratios ranging from 1:336 down to 0.996 depending on the application. Spares are still readily available in the UK (probably closest to you). Probably the easiest fix would be to change the transfer case gears from your 12C into the 355 that has the empty transfer case. probably is a different bellhousing as well but you could also change this over from your old box.
A possibility with your box having no 2nd gear is the snap ring on the front of the mainshaft has come off allowing the 2nd gear to move and not engage when the gear is selected. I have seen this happen a few times. Hope this helps.

Wonderful information! Thanks a lot!!

Krister