130 Puma diff R&P Upgrade Options

[1N3U0T]

Hello newly joined member here,
Been thrown in the deep end regarding diff R&P knowledge.

Probably talked to death, but due the need to replace diff R&P's I note there are numerous options! So what have fellow Puma owner's settled on and the outcomes once fitted? Factory OEM 3.54 ratio options are 3.5, 4.12, 4.37, 4.75

Other option KAM R&P these are 4.10 / 4.38 / 4.75

I currently have 265/75/16 tires
But looking to replace these tires with either 285/75/16 or 255/85/16 so with this in mind, what has been the best choices & why.
LT230 i have is 1.211 version
Diff are equipped with ATB's, but need new crown & pinions. Back and front!

Thanks

Cheers,

Leon

[MLD]

For a Puma with the MT82 gearbox you don't want to venture too far from the factory 3.54 with anything less than 35" rubber. To put it in perspective going to 4.11 ratios you need to fit 37" rubber to return the combination back to the same rpm as 3.54 with 235/85r16 rubber. The MT82 is sufficiently low geared that you won't notice 33" rubber. Save your money for other mods. If you need new C&P stay with OEM.

MLD

[MLD]

play with this calculator to determine the effect of a ratio change.

Ashcroft Transmissions - Ratio Calculator (http://www.ashcroft-transmissions.co.uk/calc/ratio_calc.html)

I will add, i have a Puma with 4.11 ratios with 35" rubber. The Ashcroft calculator says the overall effect is 8.6% reduction in gearing, which is confirmed by my speedo. I run about 13 km/h over the GPS speed at 100km/h, allowing for the usual 5 km/h over read on the speedo i have 8% reduction in gearing. And yes it's like driving a tractor on the road, i am changing into third as i cross the far side of a 4 lane intersection.

MLD

[1N3U0T]

I have settled on std new C&P with upgraded centre ATB & new drive flange, bearings & seal. Question is where can you buy shims to correctly mesh the crown to pinion please.

I have considered finding another puma front axle and diff and reconfigure (chop) to be in the correct orientation and fit a rear HD R&P with long nose diff.
Has anyone done this already on a Puma? Heard of Salisbury fitting is straight forward?

Cheers

1N3U0T

[clive22]

Hi

Any rover parts supplier should be able to supply them. Get parts number from website like LR series which have comprehensive listing, maybe just order a stack in advance might be easier

I thought you only need shims for the pinion depth, backlash is by the turn dial. You shouldn't need to adjust the pinion when installing another center. It s been a long while since I did mine so this may not be quite true

I have just ordered a pegged 130 P38 diff with ashcroft locker (complete bolt in assembly) for my 130. Having gone through deliberations like you.

I have ordered HD axles and flanges for both ends.

Clive

[1nando]

Hi Clive,

Hows the pegged p38 going? Did you retain the standard C&P or did you use a upgrade with the locker and pegging?

[Mercguy]

Not sure how you're going but posting this for reference.
3.54 gears on 32's with MT82 119592
4.12 gears on 32's with MT82 119593

Not sure if you're used to changing final drive ratios, but at least with a Landrover you can further augment your high range by changing out the transfer case gears, if you find that the RPM's are not ideal.

Sometimes it is a combination of CW&P as well as transfer case gears that nets you the 'right' final drive for your particular application.

It's far more important to get the torque curve matched to the wheel speed.

Knowing how much torque you can push to the wheels is half the battle.

a Dyno is very useful for this - as they not only give you a 'max power' readout, they can give you torque at the wheels in each ger for the engine RPM. Far more useful for making ratio adjustments than outright guesswork.

The ashcroft calculator is quite comprehensive for the mathematics. To make it effective though, you need those torque figures from the dyno to confirm if the engine can actually pull that particular gear at those RPM's with the weight you have.

Of course, that last issue - i.e. the GVM one, is another spanner in the works. because you also have things like roofracks etc creating additional drag (increase in the coefficient of friction) which placed additional load on the engine and can totally stuff up your choice of final drive.

Just some things to consider.