253 converted Land Rover Series III Diff Options?

[spannercrab]

Hi,
I'm asking this for "a friend" who has a S3 Land Rover with a 253 up the front and a LandCruiser HJ60 box behind it. Running 31's I believe.

Problem is she sits on 3000rpm @ 90kph - can't achieve 100kph due to the gearing.

Putting a 5-speed in her would be helpful, but only by 20% or so - what are the options in the LR's in terms of diff's - what ratios are available and what sort of other centres are able to be swapped out without too much trouble?

Any help appreciated. Any other suggestions welcome also!

Cheers

[Slunnie]

From the factory there are 4.7's and 3.54's, the latter being very common, but no doubt the 4.7's being what you have.

[F'n_Rover]

Another option (maybe not the best though) - Overdrive transfer case gear set. I've got this in my S111, 2900 revs at 100k, 3200~ at 120k.

will set him back $800 + any other parts required fo a case rebuild. It's a good option imo as low range is unchanged.

bolt on overdrive is another option, but they are shit.

5 speed - AFAIK the supra and lux boxes have the same mounting, supra adapters to 253 should be a common thing. Not sure on the lux 5th gear and high range ratios though.

[spannercrab]

Hmm ... all very interesting - I think the torque band on the 253 is pretty low down, esp with standard cams so the diffs (for a start) would be a good place to start ... then maybe an overdrive gear set ... not a lot of real low range stuff done, so shouldn't be a problem in that regard.

I've heard some rumours that these (salisbury's?) are pigs of things to change - is that right, or are they just a drop in / drop out thing?

Thanks for the replys!

[HSV Rangie]

CHANGE DIFF RATIOS AS LAST RESORT.

fitting lower (numericle diff ratios) will affect of road ability you will loose crawl speed.

o/drive will solve all the issues.

Michael.

[Mark2]

What transfer case is he running? If its a landcruiser x/fer, changing to 3.54 centers is probably the only realistic option. Defenders run this ratio, the 253 should have enough torque to pull it. If using a Series 3 x/fer, I would go with a high ratio transfer case as an overdrive wont last long behind a V8 and are hard to find in good nick these days anyway.

Suitable 3.54 front centers can be found in rangies from the 70's and 80's, 3.54 salisbury rears can be found in Stage 1's, 110 counties and Defenders up until recently. With a 3.54 center, he will be doing 2510 rpm @ 100 km/h or 2260 @ 90km /h.

But salisbury centers are not easy to change - requires a special spreading tool and pinion needs to be reset. The front center is easy (in comparison)

[spannercrab]

Hi Mark,
Thanks for the reply - yes it is a standard 60-series split case. Which limits the options somewhat. I'm not particularly fond of bolt on overdrives for these cases, as I think the same or better could be achieved with a diff ratio change or throwing in a 5-speed LC gbox & case instead (should give around 20% or so reduction in revs).

Thanks for the reply again - that info is GOLD!

[Woop]

You COULD just go all the way, and put Toyota HJ60 axles front and rear which would give you 4.1's....Easy change ,seeming as it already has Toy transmission/transfer. 4.7's would be good with bigger tyres--eg 35's, but front would be a bit marginal with bigger tyres unless you drive carefully.

Nick