LT77 again.

Crockpot · Post by **Crockpot** » Wed Mar 02, 2016 12:48 pm

As I mentioned in another question my LT77 is in a poor way. I have a spare that came with the car which I intended to rebuild.
However, I spoke to the previous owner last night and he informed me that he had rebuilt it but took it out due to a stiff and notchy shift.
As far as the bearings go it seems OK, no slop etc.
What could cause the shift to be stiff and notchy (it certainly doesn't feel good).

DaveEFI · Post by **DaveEFI** » Wed Mar 02, 2016 2:16 pm

Is it stiff and notchy on the bench - or just when being used in the car?

Is it much the same in all gears? If you disconnect the remote, does that appear to move freely?

There are lots of sliding bits in a gearbox. Some common to all gears, some only to one or two.

Crockpot · Post by **Crockpot** » Wed Mar 02, 2016 5:11 pm

It's stiff and notchy on the bench, all gears. Apparently it was like this in the car also.
The remote is not on at the moment but in the car uses a Sherpa one with cut down gear lever.

unstable load · Post by **unstable load** » Fri Mar 04, 2016 4:23 am

I'd find a friendly gearbox place and have it opened up to verify it's all tickety-boo inside while you have it out on the bench.

DaveEFI · Post by **DaveEFI** » Fri Mar 04, 2016 9:39 am

What oil is it using? Quite a lot of discussion on the SD1 Forum about what is best. One influential member swears by his own mixture of moly and a particular oil.

Crockpot · Post by **Crockpot** » Fri Mar 04, 2016 12:46 pm

Thanks for the replies guys.

Oil is unknown, it's just as it came with the car.
I'll open it up regardless and check it through. Just hoping someone had experienced this before.

DaveEFI · Post by **DaveEFI** » Fri Mar 04, 2016 2:31 pm

Crockpot wrote:Thanks for the replies guys.

Oil is unknown, it's just as it came with the car.
I'll open it up regardless and check it through. Just hoping someone had experienced this before.

I'm not personally familiar with this box since my SD1 is an auto, but many said the change from gear oil to ATF made a vast difference to the change quality. From bad to just about acceptable.

sidecar · Post by **sidecar** » Fri Mar 04, 2016 3:14 pm

DaveEFI wrote:
Crockpot wrote:Thanks for the replies guys.

Oil is unknown, it's just as it came with the car.
I'll open it up regardless and check it through. Just hoping someone had experienced this before.
I'm not personally familiar with this box since my SD1 is an auto, but many said the change from gear oil to ATF made a vast difference to the change quality. From bad to just about acceptable.

Yeah but the suppliers of the bearings which are fitted to the LT77 told Rover that they would not accept the blame for failed bearings if Rover recommended ATF! (I guess Rover ignored them!)...This is what I was told anyway!

I used Castrol SMX which is now called Castrol Syntrans Multivehicle 75W-90, it worked well as long as you allowed a couple of miles for the gearbox to warm up.

DaveEFI · Post by **DaveEFI** » Fri Mar 04, 2016 4:51 pm

That sounds incredibly thick for a cooking gearbox?

sidecar · Post by **sidecar** » Fri Mar 04, 2016 7:04 pm

I guess that's the point somewhat, the ATF stuff has a low viscosity which makes the gear change quick and light even when the gearbox is stone cold. I'd use what I (and the bearing manufacturer) considers to be a more suitable oil and warm the gearbox up. Don't get me wrong though even stone cold the gear change was OK, just not lightening fast.

The other oil that I used was Redline MTL, it also worked well after a couple of miles of warming the gearbox up. It is more or less the same viscosity as the Castrol stuff...

http://www.redlineoil.com/product.aspx?product=50204

The only reason that I changed was that you can the Castrol oil from Halfords.

DaveEFI · Post by **DaveEFI** » Sat Mar 05, 2016 8:34 am

Very interesting. I'd have thought there would have been reports of early bearing failure on the SD1 etc on the change to ATF?

sidecar · Post by **sidecar** » Sat Mar 05, 2016 9:33 am

DaveEFI wrote:Very interesting. I'd have thought there would have been reports of early bearing failure on the SD1 etc on the change to ATF?

Maybe the bearing manufacturer was being a bit to cautious or may what I was told is just bull s.... I was told this by TM Transmissions and for other reasons I would not go near them with a barge pole!

DaveEFI · Post by **DaveEFI** » Sat Mar 05, 2016 9:52 am

Really dunno. I'd always thought ball and roller bearings were about the least critical of oil of all bearing types, provided they get enough. And of course an auto has lots of them. The teeth on the gears can have a high load, though.

But I've never really understood gearbox oil theory. BMC boxes often used engine oil. Even before the Mini.

v8250 · Post by **v8250** » Sat Mar 05, 2016 12:31 pm

sidecar wrote:I used Castrol SMX which is now called Castrol Syntrans Multivehicle 75W-90, it worked well as long as you allowed a couple of miles for the gearbox to warm up.

Crockpot, as above, I too use Syntrans 75W90 and it works perfectly. There's a lot of good discussion/experience on the MGB V8 website on gearbox oil for the LT77 and R380. Nearly to a man they back Syntrans 75W90 with most seeing improved cold start up changes, smoother gear changes when hot and greater oil longevity and condition at oil changes.

DaveEFI · Post by **DaveEFI** » Sat Mar 05, 2016 3:51 pm

That's interesting. In the BL SD1 service schedule, there is no oil change interval given for the manual box or rear axle. Only top up as required. They do list a change for the auto, though, at 24,000 mile intervals.