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Transfer Box

 
     
 

LT230

My 1985 Range Rover is fitted with an LT230 transfer gearbox (so named because of the 230mm distance between the centres of the input and output shafts), which provides high and low ratios. It also contains a centre differential gear which provides permanent four-wheel drive. The centre differential can be locked in order to prevent loss of traction on slippery surfaces, but must not be locked on tarmac as transmission "wind-up" would occur.

     
         

This sectioned unit shows an
LT230 transfer box mated to an
R380 five speed manual gearbox.
The differential can be seen in the lower centre of the picture.

This shows the LT230 drive train. The input gear body is cross-drilled for better lubrication of the gearbox output shaft splines.


I have discovered that there have been a series of different LT230 transfer boxes over the years. The later types have been fitted to Defenders and Discoveries.

The serial number is stamped either on the left rear lower side (older types) or on the rear face under the PTO cover.

Suffix A:

I know nothing about this variation, nor do I actually know that they ever existed, but I'm trying to find out.

Suffix B:

This is what is fitted to my vehicle. The input gear has a relatively narrow band of teeth, with a comparatively steep pitch. As a result, it is slightly noisy. The gear is not cross-drilled and has short internal splines. The input gear on this type of transfer box cannot be upgraded to the later cross-drilled type.

Suffix C:

The width of the input gear was increased and the pitch decreased, to reduce noise. The gear is not cross-drilled and has short internal splines.

Suffix F:

This is the same as suffix C, but the input gear is cross-drilled to allow better lubrication of lengthened internal splines onto the gearbox output shaft.

Suffix B and C (and possibly A) types were found to develop wear between the splines on the gearbox output shaft and the inside of the transfer box input gear. In extreme cases this results in the splines shearing and a total loss of drive.

Land Rover issued Technical Bulletin A/B/D 415, describing the fitting of an oil feed plate to address the problem. I haven't been able to get hold of a copy of this document, so if anyone can help by sending me a copy, I'd be very grateful.

Technical Bulletin 41/06/95/EN  describes a better alternative modification, which applies only to suffix C variants. This involves fitting a replacement input gear to the transfer box, which brings it up to the same specification as suffix F.

To complicate matters further, there are different ratio variants of each suffix type of LT230 transfer box. This is noted in the two digit prefix of the serial number, which is the number of teeth on the input gear. My own transfer box has a 27 prefix, whilst the suffix C boxes have either 26 or 28 as the prefix.

In other words, before you can decide whether your LT230 transfer box needs modification and, if so what modification, it is essential to know the two digit prefix and the suffix letter of the serial number. You can find out more about this on the Ashcroft Transmissions website, which is very helpful and clear.


The following photographs show how to fit an oil feed plate.

Before doing so, consult the proper workshop manual for your vehicle, where you will find important information, including torque settings.

The PTO cover is held on by six bolts, but the holes are not symmetrically arranged and it only goes back one way round.

There are two notches in the bearing carrier to enable the bearing to be drifted out.

The outer face of the oil feed plate is clearly marked to show which way up it fits.

The two protruding pins fit into the notches in the bearing carrier, to stop the plate rotating.

The helical thrower helps keep oil inside the input gear and over the shaft splines.

This is how the oil feed plate fits behind the PTO cover.

There is a gap between the PTO cover and the oil feed plate.

Oil runs over the top of the plate and into the centre of the input gear.

The input gear on my LT230 has a dogged end to drive PTO devices.

Make sure you have the gasket correctly fitted to the PTO cover and the right way round before re-fitting.

The cut-out in the top of the plate lines up with the oil feed for PTO devices.


The following photographs show how to change the input gear.

Before doing so, consult the proper workshop manual for your vehicle, where you will find important information, including torque settings.

 
     

The PTO cover is held on by six bolts,
but the holes are not symmetrically arranged and it only goes back
one way round.

The bearing carrier is retained by
two additional screws. You can
also see the shim between the bearing and the carrier, which sets the bearing pre-load.

The input gear slides off
the gearbox output shaft.

The bearings and cross drilled holes
are clear to see
.

Here is a copy of part of the Range Rover repair manual  from 1985, showing how to change the input gear.


I would like to thank Ashcroft Transmissions for helping me to correctly identify my LT230 transfer gearbox and for supplying me with the oil feed plate.

I'd also like to thank the Land Rover Technical Academy for the opportunity to take photographs of their sectioned LT230 transfer box.


Borg Warner - as fitted to automatic versions of the later Classics and the P38a (second generation).

 

   

 

   

 

This is what it looks like with the
front cover removed. Differential
on the left, ratio change right.

 

Believe it or not, they did get all this lot
back inside the casing by the end of
the session!

 

 

 

L322 transfer box

 
 

The early L322 (3rd generation Range Rover) had a very compact transfer box. The flange on the left mates onto the automatic gearbox. The rear propshaft attaches to the flange on the right, whilst the front propshaft attaches to the flange in the left foreground and is chain driven from the torsen (torque sensitive) differential.

The selector fork changed from high to low ratio and was electrically operated by an ECU and stepper motor.

I am told this was "reengineered" in 2006/7 following the introduction of the Discovery 4 and Range Rover Sport. The new diff relies on sophisticated electronics to enable it to be locked whilst also maintaining the two speed H/L and on the move selection. The electronics integrate with the new 6 speed auto, ABS /DSC(ESP)/traction control and even the new electronic "hand" brake.