Later BTR are technically spec'ed to last 40000-80,000 miles without a fluid change (I change mine every 25,000 miles). The level should be checked at every service however (every 3000-5000 miles). If "chattering" noises occur, it is time to refresh your friction modifier. Read on.

WATCHPOINT for BTR LSDs (Limited slip differentials);

We corresponded extrensively with both the Australian manufacturers of the axle and the Morgan/BTR specialists in the UK. The ONLY manufacturer-recommended lubricant for a BTR LSD is Castrol SAF-XJ. This lubricant is easily sourced in the UK and Europe but is not available in North America and some other countries. However, a BTR was used by BMW in their Z3 range and it can be sourced under their part number (see the label image) at any BMW dealer. This product already contains the necessary "Friction Modifier" (aka Sturaco), do NOT add more. The Morgan Motor Company uses and recommends this lubricant rather than using their normal supplier of lubricants, Morris. However, we have found that Morris has often dated ideas of what should be used in Morgan axles and gearboxes. They will also not give us a comprehensive fluids' constituent list so their is no way of checking what is or isn;t in them. Considering the incidence of chattering BTRs filled at the Factory (cured by the simple addition of 2-3 onzes of FM)  and R380s gearboxes filled with ATF (unwise) We prefer to pay it safe and go with what the component manufacturers insist on.
 

Here are "possible" alternatives for those of us in North America. (I play it safe and buy at BMW.)

FLUIDS

- Royal Purple Max-Gear 85W-140 (friction modifier is already premixed)
- Red Line 80W140 GL-5 Gear Oil with Redline Limited Slip Friction Modifier
- Mobil 1 Synthetic Gear Lube 75W-140 to which one must add a Limited Slip Friction Modifier (available at Ford)

FRICTION MODIFERS

Redline Limited Slip Friction Modifier
GM Part No. 1052358
Ford Part No. F3TZ-19B546-MA
Chrysler Part No. 4318060
Isuzu Part No. 8-01052-358-0
 

N.B.The correct oil for a non-LSD BTR is Castrol SAF-XO. This is also very hard to find. Castrol SAF-XJ will do or Redline 75-140 differential oil is a good replacement as well.

Should you read or hear of any advice of ANY other lubricant for these axles, ignore it and sue the writer. (sad smile) In all the years of BTR use, the only failures heard of is from people who ignored this rule. The first sign of failure will be a clicks or light clunk with attitude changes. Damage will commence as soon as the wrong lubricant is used and will continue spreading at a rate depending on what was wrongly chosen.

To replace, take the car (if possible) on a short run to warm the lubricant a bit.

1. Place the car on a level surface.

2. Jack up the rear and remove the level plug.

[A BTR has only two plugs, one is at the bottom rear and often ignored by the uninitiated as they mistake it for a rear cover bolt). It is used to drain the lubricant. The other is a threaded plug a bit offset to the right in the middle of the rear cover. This one acts as a filler and level indicator.]

3. Remove the drain plug. (As a precaution, you can strain the lubricant to see if any debris is present.)

4. Replace the drain plug.

5. If you are adding Friction Modifier, pour it into the differential first. (from the MMC)

6. Using a container or funnel/tube that allows access to the rear filler hole, now fill the differential until the lubricant runs out of the filler hole.

7. Replace the filler plug.

8. Clean the differential and check for leakage at both plugs after your first run.

BMW and BTR recommend that the fluid level be confirmed regularly but it need only be changed every 50,000 miles.

Greasing a BTR Axle
by Lorne Goldman at the eMog Pub

The BTR axles are closed end systems. There is no need to grease them for normal maintenance as is required for the Salisburys.

Filling a SALISBURY Axle
by Lorne Goldman at the eMog Pub
 

The Morgan Salisburys are one-offs. Never used on any vehicles save for Morgans. Parts with other Salisbury (which went the way of the dinosaur in 1996)  products are not interchangeable. The rumors of an old US Jeep relationship are untrue..though some non-CW&P items are similar to the one used in the old USA Studebaker. Salisbury did not leave a supply of parts when it closed.

Aside from both being members of the Dana-Spicer group, the Morgan Salisburys have no similarity to the later (current) BTR. They should NOT be treated the same and have different recommended oils. This is very important. There are no Morgan Salisbury crown wheel and pinions, (the weakest part of that axle) to be had any longer (N.B. Billy Bellinger might be solving that now May 2011). If perfect care is not taken, or the axle is abused, the consequences are disasterous.

The recommended oil for a LSD Salisbury (Plus 8s & 7HA and 12HA) is a 80/90 Hypoy oil for limited slip differential (LSD) axles (for example Castrol Hypoy LS90 or  Mobilube Mineral LSD 80/90 or Royal Purple) . The recommended oil for a non-LSD Salisbury (4/4s and Plus 4s)  is now Castrol 75/90 or its equivalent. Salisbury axle fluid should be ideally changed at 3000 miles intervals. One cannot exaggerate the need to be careful. Never mix old and new oils. Some of the newer dealers suggest what they believe to be modern synthetic equivalents. However, the Salisbury's are not noted for strength and there are no longer parts available. A chipped Crown Wheel and/or Pinion will and has sidelined many Salisbury Morgans indefinitely. As Salisbury's original recommendation has worked for 60 years, so there is no logic in taking even the slightest risk. A BTR can be fit, but MMC waiting times run into many months for a BTR. The cost of the axle and labor to remove the hubs, swap and weld the brackets and install a new BTR will cost £4000.

To replace, take the car (if possible) on a short run to warm the lubricant a bit.

1. Place the car on a level surface.

2. Jack up the rear and remove the bottom plug of the differential and allow the lubricant to drain. (As a precaution, you can strain the fluid to see if any debris is present.)

3. Replace the bottom plug.

4. Remove the filler plug located at the rear right of the differential.

5. Remove the plug at the top of the differential.

6. Fill from the top until the lubricant leaks from the rear hole

7. Replace both plugs.

Greasing a SALISBURY Axle
by Lorne Goldman at the eMog Pub

The Morgan Salisbury axles have grease nipples at both ends near the hubs. They can be accessed by removing the rear compartment panel or from underneath. Unseen but placed placed opposite of the nipple on the axle shaft is a excess grease hole. This is often encrusted with paint or dirt. Scrub and clean the area with a solvent if you have not used it before. It is important to have it usable as it tells you when you have greased enough (the two axle sections take a LOT of grease!) and if it is too blocked it can force the grease to dislodge your bearing on that side.

The greasing is simple. Simply pump until you see a thin "worm" of grease coming out from this hole opposite the nipple. Repeat for the other end of the axle. Grease at 3000 mile intervals.

Greasing a Morgan PROPSHAFT(4/4s, Plus 4s, Plus 8s and Roadsters)
by Lorne Goldman at the eMog Pub

The Morgan propshaft has not changed much in 50 years...at some point the splined end of the longer section changed from metal to neoprene but little else of note was altered. From time to time, if it is out for a period for another reason, it is could be wise to have it tested for balance, as an unbalanced propshaft will cause vibration.

Sadly, though it requires very little care, it often doesn't get ANY! It needs to be greased and have come across many they haven't been seen a grease gun a decade and more after they left the Factory.

The propshaft has three grease points. One within the rear u-joint that it is bolted to the axle, a second at the front on the body of the propshaft that fills the propshaft itself and a third on the second u-joint at the front of the propshaft that is bolt to the output shaft of the gearbox.

The rear grease point is accessible from underneath or above  the axle compartment. Raise the rear of the car and turn the rear wheels until you see the grease nipple and you have a good line on it for your greaser. The front two grease points are accessible from underneath the car or from an access panel at the right or left at the rear of the gearbox cover. The access panel will vary in placement or sometimes not exist at all!