Hi,

Looking for Overdrive for LT95 or any idea to get higher gearing on LT95/diffs on my 101 ambulance.
Any help welcome.
Regards

hi, an overdrive or higher ratio transfer gears will help without compromising your speedo accuracy. The other route is change the diff crownwheels and pinions for 4.7:1s out of a series 3 lwb rear axle or 3.54:1s out of 110 rear axle. The only problems with diff ratio changes is that it messes up speedo accuracy and its not easily undoable if its too tall. I would suggest the overdrive route is the best although they are getting a bit pricey!!

Adam............intrepid restorer of the shed

Just a warning, if you still have the standard 3.5L engine then you might find your self disengaging the overdrive at the first sign of an incline, especially with the extra weight of the ambulance body.
Nick

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Internet Officer
101 Forward Control Club and Register

Just my thoughts..

The high ratio gears mod would probably be simpler/cheaper/stronger than trying to source and fit an overdrive.

It may be possible to fit a mid range higher ratio transfer gear out of a RR box as I think there were various options (anyone got a workshop or haynes manual for early RR)

I'm not convinced that an overdrive would survive long term on an ambi, it's fine on a GS but they're usually running unladen so only 2t against an ambi's 3.5t.

Cheers
Dave

Thanks for hints! Indeed Im bit worried about o/d durability.

Ive already grasped about 3 gearing options on LT95 (esp rangie ones) that might be the way to go !

Another option is diff pinion/ring change to the def 110 ratios , going from 5.7 to 3.75 etc.
although not sure it will work with the casing and so called buffy half-shafts of 101 . Anyone tried this ?

With regard to overdrive longevity on an ambo or any other 101 i am not really in a position to comment as i have only recently the overdrive to my GS (68FL48 the shed).
However i spent a great many years using rangerovers with overdrive on with both v8 petrol and perkins 3.8 diesels doing in excess of 30k per year and regularly loaded with 3/4tonne in the back and a fully loaded 3.5 tonne trailer behind and have never destroyed an overdrive . Although i have destroyed one or two on series landrovers (different overdrive) doing the same job.

Adam.......intrepid restorer of the shed

For 4.7:1 use the salisbury diff from a series 3 109 rear axle.

For a 3.54:1 use that from a 110.

The 4.7 crown wheel and pinion will fit straight onto the carrier in the 101 diff.

The 3.54 crown wheel and pinion need the carrier from the 110, but the internal side gears need to be transferred from the 101 carrier into the 110 carrier, so that the bigger 101 halfshafts will fit.

I've got the 3.54:1 crown wheel and pinion in my 101, but it has a Perkins diesel which produced twice the torque at half the revs of the V8. 3.54:1 axles for the 3.5l V8 petrol is way too tall gearing for the 101 with 900R16 tyres; it is after all, a 57% increase.

Going for 4.7 diffs will be an 18% increase, not too severe, but don't forget, this also affects low ratio.

Changing the internals of a salisbury diff is not for the faint-hearted, the axle needs to be sprung open to release the bearings, and when re-fitting the pinion, significant torque needs to be applied to collapse the special spacer the the right degree. And there are two of them.

I'd stick with changing transfer ratios. If you look up past articles in SixStud, you will find full details (including part numbers) of all the options ever fitted to LT95 gearboxes. (Issue 39, pages 19 and 20).

Roger.

Thanks for the very usefull info!

In such case higher gearing seems to be easiest way to go !
Im not going to do engine swap, as I want to stick with relativelly original config.
Diffs mod seems to be some challenge , especially dismantling front one with CV joints and balls.
Will try to check SixStud for the gearbox gearing changes.

I have a 101 ambulance body still with its original 3.5 V8

It's in the middle of a conversion to a camper with the rear extended and a side door in now. Before I started I had the mechanicals all looked at and sorted to ensure I wasn't building good onto bad.
Everyone knows the fuel consumption can get a bit aggressive so I wanted an overdrive. I managed to source an ebay example that came off a 110 being dismantled and was pleasantly surprised to see almost new looking gears with almost no wear. I've had an old 2 door range rover with an overdrive in the past that used to get 30mpg on a very long trip. Wont get that with this of course.

The mechanic, James, that looks after the 101 and my series 2 was very clear about the difference between the series and lt95 overdrives. I did have someone warning me about the potential weakness of it in my 101 when at the LRO show but the mechanic is adamant these are much stronger. There isn't much oil capacity so if it runs low from leaking it can be toast but he was very reassuring about an overdrive for the lt95 as long as its maintained.

I actually drove it in a big hurry from the show doing 70 plus all the way back and its much better up the inclines than my series 2 petrol. You are never going to win any races - its tortoise not hare. it was very happy to wiz along with limited gear changing except the steeper inclines but leave overdrive in and go into 3rd.

I have been really glad I've had it fitted - its a bit stiff using the cable engage and disengage but you quickly get used to it. I've been strongly reassured unless you're very heavy handed that all will be well. James always knew I was making a camper and he wasn't bothered about the weight load on the overdrive. If it goes bang I will let you know!

A word of warning though - keep to 55mph as at 70+ it turned out to run at an alarming 8mpg!!

Biggest issue is to get a good one - there is a really good you tube video of how to inspect and check one out really easily through the small inspection hatch it has (you need a screwdriver to remove it to look in). It let me buy one with confidence knowing more than the person selling it.

Best of luck!

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101 ambulance body getting back on the road and fitted as a camper.
series 2a (early) with a few updates