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Landrover Differentials


Dengie Boy
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I have an 87 RR Classic V8 3.5efi, ZF4HP22 gearbox, LT230T transfer box, 3.54 diff with 4 bolt flange and 10 spline shafts. Tyres are 235x85x16 (32inch) and yes, its now overgeared :(

Im looking to change the gearing by swapping the diffs for a 4.11 or higher from another landrover.

Can anyone tell me what landrovers were fitted with these diffs and would they fit my classic?

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Series axles are a better ratio, but I am not sure how strong they are.

I am surprised you find the setup you have over geared - I ran (and many many people do run) a rangie with exactly that with no problems on and off road and currently run a 90 with the same setup.

I wouldn't bother personally unless you are intending to go bigger on the tyre front at which time you had better start talking to Mr Ashcroft... ;)

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I have an 87 RR Classic V8 3.5efi, ZF4HP22 gearbox, LT230T transfer box, 3.54 diff with 4 bolt flange and 10 spline shafts. Tyres are 235x85x16 (32inch) and yes, its now overgeared :(

Im looking to change the gearing by swapping the diffs for a 4.11 or higher from another landrover.

Can anyone tell me what landrovers were fitted with these diffs and would they fit my classic?

Sounds like the engine is way down on power .......... the 3.5EFI was notorious for excessive cam wear...........the engine will sound ok and run fine, but wont pull the skin off a rice pudding !

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Its overgeared with the big 32inch tyres as acceleration is slower and it keeps dropping down a gear when in top. Last time i towed my caravan with this setup, it spent most of its time changing down to 3rd gear.

I cant go back to smaller diameter tyres so ive got to alter the gearing somehow, this is where i thought it would be easier to change the diff ratio, or am i barking up the wrong tree :unsure:

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Sounds like the engine is way down on power .......... the 3.5EFI was notorious for excessive cam wear...........the engine will sound ok and run fine, but wont pull the skin off a rice pudding !

Engine is ok as ive rebuilt it (new cam 5000miles ago) and its got plenty of pulling power when you hit the kickdown and accelerate up the gears.

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I think you mean under-geared, over-geared would be too tall. Your best bet is to alter it at the transfer case.

I sure its overgeared, as when in top gear cruising at approx 55mph the revs start dropping until it changes down gear back up to 55mph and keeps doing this. If i keep the revs up at 55mph my foot is nearly flat on the floor when towing.

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Ok ...... what ratio is the transfer box .............. if it is a 1.2 ( RR/disco) then yes the gearing will be too high ........... I had a similar issue with a RR transplant into a defender and changing to a 1.4 xferbox (Defender) made all the difference.

Changing to 4.11 aftermarket diffs or changing the R&P yourself is much more expensive but would give some wider options for tyres.

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I would agree that you are probably over geared.

Last summer I fitted a ZF auto to my 3.9 V8 Ninety. I already had a 1.22 ratio transfer box, which is what I expect you have. At the time I was running 265/75s (about 31.5" diameter) tyres and felt the gearing was rather tall. Once the auto has locked up in 4th the ratio is higher than 5th in a manual (from what I have read), and is decidedly asthmatic at this point, especially on motorway hills, always needing manual shifting into 3rd.

Now I'm running 255/85s (33") it's even worse. 2500RPM at 70 MPH may sound good for economy, but it makes for a less relaxing drive, especially with a trailer.

My solution will be to fit a Defender 1.4 ratio transfer box, which should bring high range to a sensible gearing. I'm not so worried about low as the V8 has plenty of low speed grunt for my needs.

Incidentally the 4.11 ratio ring and pinion set offered by Ashcrofts works out about the same change in gearing as changing the transfer box, but it will change your gearing in low range too. Note that they say these are for fitting to 24 spline units, not 10 spline.

Useful gearing calculations here.

A transfer box change is a pretty simple job. Changing diff R&Ps is expensive, and if you then manage to break a diff you won't be buying a cheap 2nd hand bits to fix it.

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2500RPM at 70 MPH may sound good for economy, but it makes for a less relaxing drive, especially with a trailer.

A 3.9 V8 should be able to cruise happily at 2500rpm at 70mph....

Peak torque occurs right around there, and some quick fag packet calcs shows that you should have something like 110hp available at that RPM, ie the same power as a TDi can muster anywhere in its rev range...

It would suggest to me the problem isnt the gearing, but the engine!

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A 3.9 V8 should be able to cruise happily at 2500rpm at 70mph....

Peak torque occurs right around there, and some quick fag packet calcs shows that you should have something like 110hp available at that RPM, ie the same power as a TDi can muster anywhere in its rev range...

It would suggest to me the problem isnt the gearing, but the engine!

Indeed, once the engine reaches 2500 RPM things start to look rosy again, and acceleration beyond that is pretty brisk for a Defender. The problem area is 1900 RPM (55MPH-ish) when the box locks into top, up to about 2200 RPM when it really struggles.

Granted, my engine is not in its first flush of youth but, as the OP has experienced, it does pull well with a manual down shift.

One other point to throw in is that the Defender 50th suffers similar gearing issues with its standard 1.22 trf box. Fitting a 1.4 box is a very popular mod among 50th owners and produces some exciting results. :ph34r:

I have to agree with what BBC says. Will be doing it myself soon. Will report on the results.

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ye i guess 1900rpm at 55 is a bit different, and in a 5 speed box you'd just leave it in 4th, but i guess with an auto its not as simple as that and the gears are wider spaced.

I'll need to look at the gearing i'm going to end up with on mine, as i currently have a 1.2 box for it, and compare it with the car to see how its going to fair on the motorway etc. From memory the A4 crusies somewhere over 3krpm at "motorway speeds", but i do know that if you do drop much below about 55-60ish in 5th it becomes a bit of a sluggard and you need to drop to 4th if you want some accelleration, so its not that abnormal.

I have a gearbox graph somewhere, so i'll dig it out and plot the numbers and see how it looks. Maybe post the results between a 1.2 and 1.4 box for reference.

People do seem scared to move out of top gear once "at speed" though, and its often to detriment of performance and fuel consumption. Dawn would often bury the foot into the carpet in 5th gear at 50mph on the motorway when coming out of roadworks or contraflows or even traffic congestion, whereas slotting it down to 4th gives a lot more acceleration with half the throttle.

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I have a gearbox graph somewhere, so i'll dig it out and plot the numbers and see how it looks. Maybe post the results between a 1.2 and 1.4 box for reference.

Good gearing info chart to be found here, might save you the trouble. Of course you'll need to factor tyre diamter on top of this :)

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A 3.9 V8 should be able to cruise happily at 2500rpm at 70mph....

Peak torque occurs right around there, and some quick fag packet calcs shows that you should have something like 110hp available at that RPM, ie the same power as a TDi can muster anywhere in its rev range...

It would suggest to me the problem isnt the gearing, but the engine!

Micky has it on the money …………… and I guess the RR wont be hugely different...........

Assuming the engine is in good nick, then a 3.5 / 3.9 in a 90 with a 1.2:1 xferbox produces what I would call marginal gearing ………. With a manual box that makes 5th gear 29mph / 1000rpm which is slightly too high when the vehicle weight / cd is taken into account. With this gearing 70mph is 2409 rpm, which is under the peak torque band for the EFI engines. This makes changing down to 4th more than an option on short steep hills and long motorway type inclines. However, 4th is slightly undergeared @ 22.37mph /1000 rpm. Put a reasonable weight trailer onto this combo and driving is very laborious indeed.

Changing the above to a 1.410 xfer box provides for a much more spritely drive. 5th now becomes 24.73mph /1000 rpm making 70 mph 2831rpm which is bang in the middle of the peak torque band for the EFI engines.

I guess a 4.6 may be OK with the higher ratio box but the 3.5 / 3.9 certainly isn’t as proven with the 50th 4L defender.

Leaving the xfer box at 1.32 and changing the diffs to 4.1 gives a very slightly higher gearing than a 1.4 xfer box and std diffs, however, as has already been noted, with 4.1 diffs you get the benefit of overall lower low range gearing.

Having driven most of the above combos I would summarise with,

Def 90 with 3.5 / 3.9 and 1.2 xfer box :

Tedious to drive solo but liveable with. Put a decent trailer on this combo and the lack torque sdue to the high gearing becomes more than annoyingly evident.

Def 90 with 3.5 / 3.9 and 1.4 xfer box:

Very spritely to drive solo and will definitely keep up with other traffic. Excellent combo with a decent trailer attached.

Def 90 with tuned 3.9 and 1.4 xfer box:

Positively frightening solo when driven with vigour and will reach a measured 3 figures (at these speeds 3 lane motorways suddenly seem very narrow).You get some very strange looks when in lane 3 of the motorway and flashing your lights to pass !

Will also pull 35inch tyres with ease (26mph /1000 rpm)

Will cruise with a 2 ton trailer all day at 70 +, although frequent fuel stops are evident.

Def 90 with tuned 3.9 and 1.4 xfer box and 4.1 R&P:

You are now into butt clenching acceleration with a vehicle that weighs 2 tons and has the handling characteristics of a sick wheel barrow.

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Ye, i'm just wondering if i should stick with this 1.2 box, or change it now :(

My motor does have a little more torque than a rover:

a8v8.jpg

But it does seem that fifth is going to be a little bit too long.

Anyone know if they do the LT230Q in 1.4:1 ratio?

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