About 18 months ago in 2016, I looked into this after some suspected gear-selection problems on our 214 R65 gearbox. The guy at a local gearbox repair firm, recommended using Automatic Transmission Fluid (ATF) in the box rather than 75W-80 GL4. I had tried EP80W-90 but without any real improvement in the performance, and he thought this oil would be too thick in cold weather and make gear changing difficult. I drained it out and put in Dexron III ATF. With the gear-change mechanism sorted and the ATF in the box, the transformation is remarkable. It's very slick, like a new car. Previously I have been using Total BV 75W-80 which was the oil originally specified by Rover for this box in 1990. Other Club Members have suggested using MTF-94 gear oil
I wonder if other owners have tried ATF in the R65 box and whether there might be any concerns that it isn't providing as much protection for the gears and final drive as GL4. I suppose if it's good enough for the gears in an automatic box, it should be OK in the manual. The guy from the gearbox firm said that quite a lot of manual boxes now use ATF and it should be no problem, particularly with a bit of the EP still left in there. Another similar firm in Rutherglen, “Top Gear”, also recommend ATF in manual boxes, see
http://www.topgear.uk.net/faqs.html
Here's a small table of the specs for the viscosity of various oils at 40 degC and 100 degC. Total BV 75W-80 was the original specified oil for this box. It looks to be quite a thin oil relatively, somewhere in between MTF-94 and Dex III. Another possible contender is Castrol Syntrans, another thin MTF.
Gear Oil, Viscosity 40 degC, Viscosity 100 degC
Castrol Syntrans FE 75W, 32.2, 6.3
Castrol Dex III ATF, 35, 7.2
Castrol Syntrans B 75W, 37, 7.3
Total BV 75W-80, 49, 8
Texaco MTF-94, 53, 10.5
Fuchs 75W-85, 81.5, 12.1
Castrol EP 80W-90, 133, 14
I used the Dex III ATF for about three months with good results, and then drained it and replaced it with the original Total BV 75W-80 I’d taken out earlier. The feel of the gear change isn’t markedly different. Perhaps a bit more notchy, and slightly harder going into first and second gear. I think in a little while I’ll revert to the Dex III as it gives a smoother slicker feel to the gear change. Changing the oil in the Rover 214 gearbox is a bit of a pain as the top filler hole is rather inaccessible. I’ve made up a right-angles tool out of some 15mm plumbing bits, with the pipe narrowed down to go into the gearbox filler hole. It’s also easier to screw the filler bolt back in from under the car.
18 months and several thousand miles later using Dex III, the gearbox is performing well without noise or gear selection problems, apart from occasionally being reluctant to go into fifth gear. We've just returned from a 1100+ mile road trip without issues on the gearbox.
Hugh
