LT77 again.

v8250 · Post by **v8250** » Sat Mar 05, 2016 4:37 pm

DaveEFI wrote: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.

It's an interesting discussion...I'm an old fart when it comes to gearbox and differential oils, even when the schedules say top up only required, I change both every 3-5 years irrespective of mileage. I find it a useful exercise in knowing I'm doing the 'right thing' for 'box/diff' longevity, check internal condition, colour, swarfing et al.

Inversely, I have a buddy who's heavily into zero cost bangernomics. He takes my spent oils and uses them in his snotters. We feel great as we're doing our 'thing' for environmental recycling

DaveEFI · Post by **DaveEFI** » Sat Mar 05, 2016 4:51 pm

I was going the change the rear axle oil in my SD1. But no drain plug. So didn't bother. It's now done getting on for 200,000 miles.
The auto I do change. Again, no drain plug. That annoys when it has a scheduled change. Perhaps it's because they say to change the pick-up strainer too - but removing the sump without making a mess isn't easy.

Love the idea of using old oil. That really is being tight.

v8250 · Post by **v8250** » Sat Mar 05, 2016 6:21 pm

Dave, have you thought of tapping-in a helicoil for a magnetic drain plug? Have drilled a number of gearboxes and diffs' over the years and it works brilliantly. I've found that the new drain plugs don't have to be huge BL sized jobbies and have used Japanese metric magnetic plugs.

Even mod'ed an old E-Type Moss MOD once where some previous owner had stripped the original plug thread, gummed it up with chemical metal and re-fitted the plug whilst still wet...left overnight and refilled with oil; a real pain of a bodge to rectify. A welded blank, a new drilled and helicoiled hole + drain plug later and all was well. The car's still running with this design change 17 years later...

Crockpot · Post by **Crockpot** » Sun Mar 06, 2016 2:35 pm

Thanks for all the feedback guys.
I think I'll still investigate the box for my own peace of mind, then pay some attention to what oil I use and change periods.
I can say with certainty that the old one (still in the car) is making some very worrying noises

unstable load · Post by **unstable load** » Mon Mar 07, 2016 6:21 am

I think the thinner oil is because of the built in pump that circulates the oil in the box needing a lower viscosity, particularly in colder climates.
As far as I recall the Disco with the LT77 specified ATF, and if it's OK for such a heavy vehicle, I'd think it OK for a saloon.
If you are determined to change oils, look at the specified oil for the R380 that replaced the LT77. It's called MTF94, the R380 also has the pump in it.

Crockpot · Post by **Crockpot** » Mon Mar 07, 2016 6:54 am

Gearbox failed in spectacular style on the way to work this morning

so I'll be finding out what the spare is like a bit sooner than planned.

sidecar · Post by **sidecar** » Mon Mar 07, 2016 7:41 am

unstable load wrote:I think the thinner oil is because of the built in pump that circulates the oil in the box needing a lower viscosity, particularly in colder climates.
As far as I recall the Disco with the LT77 specified ATF, and if it's OK for such a heavy vehicle, I'd think it OK for a saloon.
If you are determined to change oils, look at the specified oil for the R380 that replaced the LT77. It's called MTF94, the R380 also has the pump in it.

MT94 is 80W-90 which is in the same range as the oils that I've mentioned.

Denis247 · Post by **Denis247** » Tue Mar 08, 2016 11:50 am

Don't use ATF. I followed this advice once and a new box lasted just a couple of years.

DaveEFI · Post by **DaveEFI** » Tue Mar 08, 2016 2:50 pm

Denis247 wrote:Don't use ATF. I followed this advice once and a new box lasted just a couple of years.

When you say a new box, did you mean new?

Denis247 · Post by **Denis247** » Wed Mar 09, 2016 11:34 am

DaveEFI wrote:
Denis247 wrote:Don't use ATF. I followed this advice once and a new box lasted just a couple of years.
When you say a new box, did you mean new?

Actually no, it was a recon. I know where you're going with this but I'm convinced using ATF was a major factor in it's demise.

Using additive ZX-1 with 'normal' gearbox oil improves the cold shifting quite a bit, but the 'box soon warms up anyway. I know people who have also used synthetic engine oil, Mobil 1, and they've had no troubles either.

Another fella I knew had a 308 Ferrari and that gearbox was very notchy when cold, which he told me all 308's are. But you just suffer it for a few miles. If the gearbox is cold so will be the engine, and you shouldn't race a cold engine anyway.
Just my 2d worth.

minorv8 · Post by **minorv8** » Fri Mar 11, 2016 8:36 am

I have used ATF in my LT77 (originally from 4-pot TR7, (the weakest of them all) behind a 4,6 engine and have not seen any ill effects. I rebuilt the box in 1998 and have used ATF all these years. Shift quality is very good. I guess each box can be different though.