Thread: LT95 vs LT77 with auto ratio LT230

I posted this some time ago in Range Rover Classic but thought I might get more varied audience in Technical.
My 82 RRC would have been delivered with an LT95 gearbox with 0.996:1 high range transfer gears as it has a 9.35:1 high compression engine.
The car has had the LT95 replaced with a Chrysler Torqueflite 727 and an LT230 transfer case that has a 1.003:1 high range.
I have bought an LT77 5 speed with an LT230 transfer case that has 1.192:1 high range transfer gears so that I can convert it back to a manual.
When I compare the overall gear ratios from the LT95 (0.996:1 high range) to the LT77 (1.192:1 high range), 5th gear is not that much of an overdrive.
LT95 = 2796 rpm @ 110 kph
LT77 = 2576 rpm @ 110 kph
See top and second table below.

In effect, the 5 speed is almost a “close ratio” of the 4 speed.

However, if I fit the LT230 from the auto (1.003:1) to the LT77, the 4th gear ratios are almost exactly the same as the original LT95 with the 0.996:1 high range. Compare top and bottom table.
Then 5th gear will be a significant overdrive for cruising.

Is it as simple as unbolting the LT230 from the auto and bolting it to the LT77 in place of the current LT230, or is there something more complex to be done ?

Has anyone done this swap previously?

Regards
Phil

I've swapped an LT77 to an Auto using the original LT230 that was bolted to the manual box in my 85RRC - it was a straight swap. The LT77's are not a strong box but with normal road use will survive ok. If you plan on offroading or towing with it, I'd think again though. If you've bought it as a secondhand used item, I'd strongly suggest getting it checked before sticking it in the car. Mine was used by the previous owners (My Inlaws) on road pretty much entirely and did tow a small van some distance but the box went from serviceable to pretty much unusable pretty quickly when they did some heavy towing with it. While it was still operational when I removed it - that was more good luck than good planning.