Thread: How to reduce drive ratio?

Just been and had a quick look under the car and the gearbox is the 50A type LT77 and the trans box is the 13D so 1.41.
With the standard R&P (3.54) and 35s that gives 2477rpm at 100kph in 5th.
2875 with 4.11
3323 with 4.75

Does 2477rpm at 100kph in 5th seam reasonable?


(This was done with the Ashcroft ratio calculator)

If you can't pull 2500rpm at 100km/h then you should be looking at the engine instead of the gearing.

Have you corrected your speedo or are you actually driving at 120?

for rover type stuff, look at Ashcroft in the UK (as you already have) and Great Basin Rovers in the USA...if you want to mod your rover housings to have all the Toy runningf gear in side them look at RoveringTracks.

I can not understand how anyone would fit bigger tyres and not change the gearing out...stock gearing is ok with stock tyres. and even then, offroad could be lower.

even LandRover themselves had lower gearing in the larger tyre'd vehicles
55-1 1st low for the 1 tonnes and 75-1 for the 101.....and the original RRC was 47-1 for 29's

If you want to change the transfercase gearing you have the option of fitting the 1.661 high range and getting some MaxiDrive low range gearsets from MR Automotive that are either a 30% reduction or 49% reduction...

No problem pulling at 100 (my speedo reads about 7% lower than actual)
It was more a case of now that I have messed with the ratios by fitting bigger tyres I should correct it.
30% reduced low range could be the way forward then I keep the long legs for highway but get better controll off it...

I run 4.11/4.12 ratios in my 110 Defender on 35's without too many problems,and mine is only a 200Tdi
So your v8 should be fine.
The lower transfer gears might be ok down the track,if you can stand the noise.But my gearbox and transfer are nice and quiet,that is why I went with an underdrive.
Not something that is really needed by the average user,but nice to have

Originally Posted by Jitterbug

Just been and had a quick look under the car and the gearbox is the 50A type LT77 and the trans box is the 13D so 1.41.
With the standard R&P (3.54) and 35s that gives 2477rpm at 100kph in 5th.
2875 with 4.11
3323 with 4.75

Does 2477rpm at 100kph in 5th seam reasonable?


(This was done with the Ashcroft ratio calculator)

My old classic set up is running 2100rpm at 100kph and are very happy with the low rev's and have plenty of pulling power.(powered by a petrol engine, 33inch tyres).

What size engine is in your car? If its a diesel how come it needs so many revs at 100kph as I thought they had plenty of torque down low?

Paul

Originally Posted by tebone

My old classic set up is running 2100rpm at 100kph and are very happy with the low rev's and have plenty of pulling power.(powered by a petrol engine, 33inch tyres).

What size engine is in your car? If its a diesel how come it needs so many revs at 100kph as I thought they had plenty of torque down low?

Paul

Rover V8 3.9 efi that has had a bit of work. Just been out for a drive and it seems fine on highway. Will have to see how the low range goes...

Originally Posted by Jitterbug

Just been and had a quick look under the car and the gearbox is the 50A type LT77 and the trans box is the 13D so 1.41.
With the standard R&P (3.54) and 35s that gives 2477rpm at 100kph in 5th.
2875 with 4.11
3323 with 4.75

Does 2477rpm at 100kph in 5th seam reasonable?


(This was done with the Ashcroft ratio calculator)

Sounds like heaps of revs to me, especially for a V8. If you are happy with the way it drives on the road, then perhaps look at reduction in the transfer case. I think that 30% and 49% low range gears absolutely transform manuals when offroading. This is what they should have had from the factory.