Thread: 1985 110 Factory Isuzu Engined Gearbox Issues

You can now get a complete steel oil pump gear for the LT95. Penrite recomends you run light motor engine oil which is SAE30. I have run this in my LT95 for years with no problems. Castrol GTX etc is no good due to the friction modifiers as has been mentioned. Penrite make a LGO80 or 85 which is very thin for late model gearboxes this should be fine with the new steel oil pumps. If you have an LT85 throw it away and put in an LT95. This is the only gearbox Rover has madfe that will handle the 4BD1 reliably.

Originally Posted by landrover dave

You can now get a complete steel oil pump gear for the LT95. Penrite recomends you run light motor engine oil which is SAE30. I have run this in my LT95 for years with no problems. Castrol GTX etc is no good due to the friction modifiers as has been mentioned. Penrite make a LGO80 or 85 which is very thin for late model gearboxes this should be fine with the new steel oil pumps. If you have an LT85 throw it away and put in an LT95. This is the only gearbox Rover has made that will handle the 4BD1 reliably.

A couple of points.
The LT85 - according to various polls on this forum, is good for up to 300,000klm. Turboing or driving long stretches in 5th & it will go down from there.
The LT95, again, according to lots of posts on the subject will need to have the taper bearing conversion to properly qualify it as "Isuzu proof"

The 0.996 high range gears have a greater tooth pitch than the earlier 1.113's. High torque motors create alot of side thrust from these gears creating enormous amounts of heat which melts the bearing cages, hence the army specced tapered bearings. I have been running the 1.113 high range for years behind a high torque 350 chev with no problems and now behind the 4BD1T.

I have never seen a LT85 last longer than about 100000k's! My last LT95 lasted 6000000k's, 200000km behind a 350 chev! My current LT95 has about 150000km up (all behind the 350) now its got the 4BD1T in front of it and it still feels like it did the day it was rebuilt. Still has the same intermediate shaft in from day 1.

Originally Posted by landrover dave

I have never seen a LT85 last longer than about 100000k's! .

You haven't looked very hard then.

Mine was rebuilt at 240000km. It now has 370000km and the engine had a T added at ~320k km.

Dave S on here used to own one with 360000km and what I am pretty sure was the original box. 3rd was sloppy as hell, but the rest of the box seemed OK.

There was a thread, I did a search but gave up, where owners submitted thier LT85 mileages. That was what I was quoting.
I know of 2 behind V8"s getting into the mid 200's. I recognize the Isuzu is harder on them, especially the front bearings, Ive got 2XLT85's with knackered front bearings. I wouldn't swear on it, but both seem original at 340,000 klm.

Originally Posted by landrover dave

The 0.996 high range gears have a greater tooth pitch than the earlier 1.113's. High torque motors create alot of side thrust from these gears creating enormous amounts of heat which melts the bearing cages, hence the army specced tapered bearings. I have been running the 1.113 high range for years behind a high torque 350 chev with no problems and now behind the 4BD1T.

I melted the cages in my FC 110 behind the Isuzu. But it weighs in at 4.5 tonne.
Are TRB replacements available. Who can we contact?

Originally Posted by 123rover50

I melted the cages in my FC 110 behind the Isuzu. But it weighs in at 4.5 tonne.
Are TRB replacements available. Who can we contact?

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cheers, DL