I have spent the day working on the transfer box.
The Roverdrive has been removed to fit a new version of the front casing, which is designed to improve oil flow through the unit as a whole but especially the front bearings, helping to reduce running temperatures. I think the 75W90 semi synthetic oil may have done the front bearing no favours, as while serviceable, it’s a bit grumbly.   I’ll be replacing that too when I can source the part, so have refit the standard transfer box input gear temporarily. I will stick to regualer mineral EP90 or EP80-90 in the future. The good news is that the gears and shafts of the Roverdrive seem to be in mint condition after 20,000 miles behind the Tdi engine and heavy motorway use.
The other transfer box related job tackled today was fitting the new 2.81:1 low range gears (part numbers 521330 and 235438). These are from Suffix B Series II Land Rovers and give a 17% lower gearing than the 2.35:1 gears used in Siffix C and later SIIs and all SIIIs (except 1-ton and V8). This will go some way to offsetting the gearing increase of the higher diff ratios in the new axles, but I imagine it could be very useful in trailing vehicles and Land Rovers used for heavy towing and over-landing with their original engines. Some of it’s a pig of a job, really, but it’s easily manageable in a day .
The first job, after chocking the wheels and draining the transfer box, is to remove the rear prop shaft, followed by the complete transmission brake drum and transfer box output flange.
Once they’re, clear, remove the brake backplate (still complete with the brake shoes and mechanism), speedo cable and the speedo housing.
Next, remove the bottom cover plate and the intermediate shaft retaining plate. Now carefully remove the intermediate shaft while supporting the intermediate gear cluster – it’s quite heavy and you don’t want to drop it. Once clear, recover the bearings from the gear and thrust washers and shims from the transfer box walls.
Here’s the hard part. You need to slide the transfer box’s output shaft aft to remove the gears, but the smaller “high range” gear is retained by a circlip. You will need mid sized 90-degree circlip pliers (that expand the clip when squeezed, not shrink) to remove the clip. It’s a three handed job, really, but I did eventually manage alone. Withdraw the shaft slowly, recovering the front bearing, circlip, washer and two gears as they each come off the shaft.
Obviously, reassembly is in the reverse sequence, and you need to make sure everything is scrupulously clean as it goes back in. The circlip must be replaced with a new one, and the new intermediate gear cluster may need new thrust washers and shims, so order a selection when you order the gears. A smear of grease holds the shims and thrust washers in place while refitting the intermediate cluster and shaft. When you refit the transmission brake backplate and mechanism to the speedo housing, make sure the operating rod’s clevis fork sandwiches the relay arm, as you will not be able to move the arm into position if it is allowed to drop under the relay during refitting.
The later photos show the new and old gears next to each other for direct comparison, and you can see how much bigger the lower output shaft gear is (black gear) and how much smaller the lower intermediate gear is (clean one). The fourth photo shows the offending circlip, just to the left of the smaller gear – access to this with the pliers is much easier with the intermediate cluster removed.
The limited run of B type intermediate gears was for good reason…weakness. Same low gearing as the series 1 / 2 but bigger stronger intermediate shaft weakened the low range gear its self, leaving not much metal for the gear wheel.
I can only imagine what it would do when it fails apart from the obvious and leave you stranded.
Thanks for the comment, and it’s a good issue to raise.
I had a good look at the gears and they have the same size teeth as the newer version. I know different gear sets for the same application can be stronger or weaker depending not just on tooth size or angle (these being more vulnerable with their straight cut low gears) but also the thickness of the base – differential gears are a very good example with 3.54 diff gears being a good deal stronger than the 4.71 gears despite the rest of the diff being the same. However, I have never heard of anyone breaking these gears. I suspect Land Rover changed the ratios simply because they didn’t need to be so low once they increased the engine size from 2l, which happened around the same time, give or take. Maybe they found they were breaking too many axle half shafts, which is a far more common failure, and sought to reduce the torque applied to them in low range by upping the gearing. I don’t know, but I’m not worried about them – they’re strong enough for the application, especially given the nature of the use of this vehicle. A vehicle driven hard in quarry play sites with enormous tyres may be different, but it’d still be the diffs and half shafts that’d blow.
Hello . where can we get the 521330 part now ? Regards
Hi Luis,
My favourite supplier is Dunsfold Land Rover. Great service, lots of stock of old genuine parts, lots of the unusual bits, and good prices.
PA Blanchard have extensive stocks of genuine components, but be warned that they are expensive.
John Craddock may have the parts, but I have found in the past that their service is, in my opinion, absolutely terrible and they lie about having stock of parts to secure customers’ orders, and then leave them waiting months while they hope for the part to arrive in their shop.
Paddock Spares may have them, but they would be Britpart copies. They would be cheaper, but may be poor quality. I do not trust Britpart quality in general, though a few of their components have been good.
Shana Piercey at Syncro Gearboxes (spelled incorrectly as their name) may be able to provide the parts or information on where to find them. Unfortunately, Ashcroft Transmissions don’t work on Series LR units.
Regards
Nick