I wanted to fit a 4.08 ratio diff in RM13, to go with the 11.3 engine that I have.
Two weeks ago I fitted a 4.77 ratio diff to RM1797, which I had built, I supplied the Crownwheel and Pinion. RM1797 now cruises at 45mph, it’s a good combination, Scania engine and a mid range diff.
It took about 4 hours to change the diff assy, that was in the Grain Barn.

I then took the std diff assy from RM1797, which was in good condition to Queensbridge and supplied them with a 4.08 ratio Crownwheel and pinion, which came out of a Reliance. They rebuilt the diff assy for me while I waited, it took approx. 5 hours, and I also got them to replace the carrier brgs.
I now have a reconditioned 4.08 diff assy to go into RM13.

I paid £70.00 for a 4.08 old reliance diff assy, Queensbridge charged £200.00 labour, but the carrier bearings were £108.00 each (2 req.) all plus vat of course. So, for a touch over £500 I now have a reconditioned diff assy for RM13.

I was considering getting some 4.08 ratio Crownwheel and Pinions made. I have made contact with the company in Spain that made the last batch of std units, but I feel at the present time that there are plenty of new std Crownwheel and pinions around, and if you are prepared to get out there, you can find good second hand higher ratio sets at reasonable prices as well.


DU17, STD RM Diff Assy 5.22 (38mph)
9 tooth Pinion
47 tooth Crownwheel

DU18, RMC/RCL Diff Assy 4.77 (45mph)
10 tooth pinion
47 tooth Crownwheel

DU24, RMA Diff Assy 4.08 (a bit faster)
12tooth pinion
49 tooth Crownwheel

ps Queensbridge has on the shelf, a std recon diff assy and a recon gearbox, I think they said the cost was £1200.00 per unit (exchange)

My bus number (if any): RT2291,RM1797, RML2261 and RM13 just about!

Rob,
How difficult is the work required to put the 4.08 ratio into a standard diff ? Other than the crownwheel and pinion is there much other new parts required.
The new diff on 1797 you had made , do you mind me asking price and who built it up for you ?

Mark 2391

ps any news on st neots

My bus number (if any): rml2391

The 4.08 ratio Crownwheel and pinion will fit into a STD diff assy no problem, however because the 4.08 uses a 12 tooth pinion, it is a larger diameter to the STD 9 tooth one. The casing may need to be relieved (ground out) to make sure the teeth do not foul the inner casing. , You would need new gaskets and a seal, if the bearings are ok they can be reused. There should be no other expense, unless you get someone else to remove and install the diff assy into the bus.
The diff assy for 1797 was built up by Lional, there was a problem with it when it was first installed, the off side halfshaft would not fit, so the unit was taken out and the old one refitted until it could be sorted by Lional, it was then refitted. The lesson is always make sure that the halfshafts fit in the new diff assy, before you fit it in the bus.

My bus number (if any): RT2291,RM1797, RML2261 and RM13 just about!