Jump to content

change the diffs or the Transfer box?


Recommended Posts

Over Geared:

I have a 3.5 carb V8 110 (early) the transfer box is 1.4:1 the box is an LT85, Im running 235/85 16

It seems over geared – I don’t often use 5th Gear and never engage the GKN Overdrive

If I wanted to change the gearing on the V8 is it easier / cheaper to change the diffs or the Transfer box?

cheers

Bill

Link to comment
Share on other sites

That is factory gearing and I think bang on with your tyres. The overdrive will be the over gearing and would think you would be better to remove it and save the weight!

If the engine is not pulling those ratios easily then I would say look at the engine. A friends V8 110 which was standard pulled really well.

Toby

  • Like 1
Link to comment
Share on other sites

Our 127 ambulance (so bigger, heavier, and even less aerodynamic than your 110) had the 3.5 V8 with those ratios + tyres and pulled 70mph / 5th gear happily enough. It does it a bit better with the 4.6 these days granted ^_^

A 110 rear diff swap will be harder than a 90 as it's a Salisbury diff, only alternative I'm aware of would be Series 2/3 109 at 4.7:1 but if memory serves that's also a "convert-to-imperial" job so quite involved, and 4.7:1 is a fair drop.

You can sell the GKN for ££££ and spend a bit of it on a tune-up of the V8, or spend most/all of it on swapping in a newer V8 with more ponies.

1st thing though I'd suggest your V8 is in dire need of a good coat of looking at as that's not right.

  • Like 1
Link to comment
Share on other sites

I agree that a V8 should pull that gearing easily. V8s are prone to wearing cam shafts out, so that is one place I'd be looking. Unfortunately, it seems all too common for LR owners to write off poor performance, braking, steering and handling as a characteristic of the vehicle and set about all sorts of alterations when it just needs faults rectifying. Many of these cars are old and hard worked, and seemingly very few are well maintained. The recent discussion about brakes in the Defender section is a good example, and there are countless threads about Series steering.

4.71 ratio diffs would be easily and relatively cheaply sourced from a SIII 109, but they'll be old and you're taking a punt on condition. KAM Differentials do a wide range of ratios for Salisbury and Rover diffs, but they cost a bit more, being new and specialist.

As for swapping Salisbury diffs, on paper it is much more complex than swapping a Rover diff, but in practice, it's not much harder. The casing is part oft he axle, unlike the Rover type, so the carrier and pinion come out separately from the casing.. That means a theoretical issue with preloads and mesh. The reality is that LR axle tolerances are good enough that there is very rarely a need to change the shims - you leave the pinion inner bearing outer race and its shims in the casing, and leave the carrier bearings and shims well alone; the cases are all accurate enough and the internals will all fit and mesh correctly, even when swapping pinions and complete carriers from case to case. It is even true if you fit the non-standard ratio KAM pinion and ring gear to the existing carrier - they give instruction on how to set up the mesh and preloads, but go on to say that less than 5% of instances need any alteration. I had no trouble changing from 4.71 to 3.54 and back again. You won't even need the axle spreader to get the carrier out, just a couple of levers and another pair of hands to handle it before it falls out.

  • Like 1
Link to comment
Share on other sites

Maybe I don’t rev it hard enough – but my early V8 motoring was with American Pick-ups with lazy V8s

My 3.5 is a long way from perfect, but – 65 to 70 MPH is comfortable / achievable in 4th which makes me think that something is ‘different’

Is it possible that despite the transfer box number suggesting that it is 1.4:1 someone might have changed the ratios at some point?

I've had the GKN from new, bought for my late wife’s 300Tdi 90 – It was never fitted (in the same period I was running my 110 300 Tdi with a GKN which was very useful especially when towing)

OD 3rd and OD 4th being particularly helpful.

I should at this point state that the Overdrive isn’t working (or ‘in’ or engaged) so is not contributing to the over gearing issue

Link to comment
Share on other sites

Easy way to tell - look at the RPM in gear at a given speed (pick any gear & any speed, 50mph in 4th perhaps) and compare with the ratio calculator on Ashcroft's website. If the numbers are way off, and switching transfer box ratios would make them right, someone's re-ratio'd your LT230. Usually people just fit a different LT230 though, not bother dismantling & swapping gears.

An old carbs-and-dizzy low-compression 3.5 V8 has plenty of bits that can get old, tired, out-of-adjustment, gummed up and generally in need of love. If it's original it may even have restrictor plates in the carbs, although most of them were ripped out at the 1st opportunity many moons ago.

Until you've done a basic service including checking ignition timing/advance and carb adjustment / balance it's not even worth talking about other stuff. Costs peanuts too.

Link to comment
Share on other sites

I've got the same set up (110, V8 on carbs running 235/85 on LT85 gearbox). I fitted a Discovery transfer box to mine (higher ratio) and it could still pull over 70 on a motorway towing a 1.5 tonne trailer. Motorway hills slow it down so I'll probably go back to a Defender transfer box.

But as others have said, I'd look at the engine first rather than changing diff ratios.

Link to comment
Share on other sites

In some ways I'd be quite happy if it were a tired engine - then I'd know what the issue is, and I'd have a good excuse to take it out in favor of a bigger and rebuilt lump.

The engine isn't original, this was once a Turbo Diesel - the 3.5 serial number suggest that it was once at home in a 130 Ambulance / rapier tractor.

But No one who has driven it,or was involved in the rebuild, (as in new chassis and bulkhead) or who has serviced it, has ever suggested that it is tired?

I appreciate all the help and advice here because I feel I'm stumbling around in the dark.

I've got the same set up (110, V8 on carbs running 235/85 on LT85 gearbox). I fitted a Discovery transfer box to mine (higher ratio) and it could still pull over 70 on a motorway towing a 1.5 tonne trailer. Motorway hills slow it down so I'll probably go back to a Defender transfer box.

V8 Pete sort of makes my point in favour of the GKN OD You have a lower ratio box, then use the Overdrive on the motorway, dropping the OD out for the hills

Link to comment
Share on other sites

You have standard gearing, so unless you have something dragging, like seized brakes, then the engine performance must be down. Just because nobody has pointed it out before doesn't mean that it's performing correctly; it is quite possible to have an engine start easily and run smoke free while being low on power, especially a carb fed engine.

Link to comment
Share on other sites

The RV8 will run like a sewing machine whilst totally knackered, they're very tolerant of wear. Also the ignition system can be weak (especially non-genuine parts) and carbs do need maintenance. That engine with that gearing will pull a 130 along at 70mph in 5th, because they came from the factory with that exact setup.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy