Diff pinion thrust bearings

[Nick Mayne]

I have a pair of R&M LJT1 angular contact bearings that fit in the separate housing of a D-Type back axle. I have fitted them with the 'thrust' engraved faces together. Is that correct?
Tony Press published a 'How To' article about these stating that using standard LJT1 bearings in a later D-Type back axle would result in the pinion moving forward by 1/32" unless one carried out some machining. He stated as an alternative there were special versions of these bearings made with a reduced width outer race on the non-thrust side.
I do not understand why the bearing outer race width could cause this problem or be alleviated by reduced width so maybe someone can explain that?
My LTJ1 bearings do have the reduced width outer race on the non-thrust side so I guess I am ok with those although I cannot see any markings to say they are not standard bearings.

[Tony Press]

"I have a pair of R&M LJT1 angular contact bearings that fit in the separate housing of a D-Type back axle. I have fitted them with the 'thrust' engraved faces together. Is that correct?"

They should be mounted "back to back'


  Angular Contact Brgs.jpg (Size: 7.3 KB / Downloads: 382)

In the case of your narrow outer ring bearings, if they were incorrectly mounted face to face there would be 60 thou preload !

   

Edit- This drawing shows the first AC bearing mounting with 'Ring Nut' or 'Outer Distance Piece', later changed to a two piece housing- see below. 

The axial position of the pinion is governed by the outer rings of the angular contact bearings held in the torque tube housing.

All the original AC bearings fitted to the Austin 7 had outer rings 1/32" narrower on the non thrust side than the standard width inner ring and fitted back to back on the pinion.  

All modern AC Bearings have outer and inner rings the same standard width.

With the outer ring narrowed by 1/32" on the non thrust side then the pinion is located 1/32" forward on the position it would occupy with a full width outer ring bearing.  

The bearing housing is also relieved on the pinion side AC bearing so the pinion radial bearing takes the radial load.

   

Hope this clarifies the rather confusing pinion bearing AC mounting.

Edit- In 1933 the torque tube AC bearing mounting was changed. The Ring Nut or Outer Distance Piece was replaced by a two piece housing. With the bearing tolerances and housing machining tolerances this could cause a slight end float in the AC bearings which must be removed.

   

[Bob Culver]

Current off the shelf ac bearings can be used in either configuration altho back to back give superior rigidity, an advantage in some 
applications. (I ponder if crank ac would be better mounted front to front)  Precision matched pairs only go one way and the narrow rings ensured this. Also ensured one not reversed (Any and everything is found in old cars)
Old bearings if all smooth can be reused. Can shim for very slight preload.

I cannot immediately fathom the 1930 set up but gather not what you have.
Whatever bearings used the outer rings must be clamped axially. The pionion space lenghth must be such that a reasomabe space for shims is allowed at the diff flange.

The oil seal arrangement is not as all.

If sumwun can explain the 1930 diag would be interested pse.

[Nick Mayne]

Tony thanks for the diagrams as 'back to back' which I have seen before di9d not mean anything to me. So my thrust face to thrust face is ok.
I misunderstood the bearing discussion referring to reduced width outer races as I assumed that meant the actual wall thickness having noted that mine are like that one side to the other. However referring to the width of the bearings I can understand the 1/32" difference if those bearings were to be used.
I am fitting one of David Cockrane's new form CW&P with the 5.67/1.0 ratio. The new shaft is 1" diameter behind the pinion gear not as my old one which was 1.125". So I am waiting for the appropriate ball race 1.0 x 2.5 X 5/8 but also have to have a new spacer made as my old one is 1.125 clearance ID. I had hoped to find a roller bearing but the only one available is 3/4" wide and if the spacer was shortened by 1/8" it could prejudice the shimming available in/out adjustment. Also the outer race retaining spring ring would be further out.
Thanks to every one.

[Stuart Giles]

The spacer depth needs to match the bearing setup that you decide to use.

The roller bearing spacer you have should have started out @ 3/4" deep IIRC. This works with the 5/8" wide 1 1/8" bore LRJ 1 1/8" roller bearing fitted to later rear axles.

The earlier car ( '31 on) had a 5/8" deep spacer which works with the 3/4" wide factory fit MJ1 ball race on the 1" pinion.

In either case the pinion ends up in the same place axially vs. the pinion thrusts.

[Nick Mayne]

Well I need more help! The pinion bearing arrived today but it is 3/4" wide and is a deep groove ball bearing. That means it will not slide within the outer race and as the depth in the D-type axle casing is controlled by a stop peg it will not allow in/out slight adjustment of the pinion when setting up the CW&P. I can get a sliding roller bearing of the same size albeit at a higher price. Also the 3/4" width instead of the original 5/8" width may affect the available in/out adjustment available as the angular contact bearing housing may not leave space for the shims. (I have the separate housing configuration that holds the two angular contact bearings discussed above and in a D-type axle. It would be good to talk to someone who has put the new 1" pinion gear shaft* into a D-type axle.
(* the CW&P are new to the 5.67 ratio with the new tooth form but pinion shaft 1" diameter for the gear bearing instead of the old 1.125")

[Stuart Giles]

The peg is there in original fit roller bearing axles to stop the 5/8" width roller race outer ring/track wandering towards the crown wheel. If you are going to use the 3/4" wide ball race, then just remove the peg. If you are going to use a 3/4" wide roller race you will probably need to cut back this peg, or even remove it to allow enough room to seat the wider outer track.

All the rear axles I have done which had a 1" pinion have either had a 1" bore sleeve Loctited into the late style 1 1/8" roller race, or have had a 1 1/8" OD sleeve Loctited onto the pinion to accept the roller race.

[Steve Jones]

If you come to remove the peg, you'll find that it screws into the casing. If it stays removed, you'll need to seal the resulting hole in the casing or the oil will fall out! The one I have is sealed with a suitable length set screw - 1/4"BSF from memory.

Steve

[Bob Culver]

In our ownership my RP spent its early and last serious use life in an alpine suburb of Wellington NZ. Approach from anywhere involved 1 1/2 miles  in 3rd and 2nd.
On purchase in 1940 the diff was noisy and my father replaced the pinion bearing at 43,000. He was very fastidious and repeated at 75000. I changed the diff at 110,000 for a Girling type but sounded OK then. Modern bearings are made of vacuum degassed steel and have a much higher rating than 65 years ago. Incidentally, axles never replaced....or lapped...
As above one disadv of the ball race is that it is not easy to repeatedly withdraw the pinion to check mesh. Some apparently set up with the casings split and apparently is OK. But if an old reasonable bearing is available this can be relieved on both diameters and when setting established the new bearing fitted for final assembly.

[Nick Mayne]

I think I will have the 1.1.25" diameter restored on my new shaft using a sleeve and probably a new 1.125x2.5x5/8 roller bearing although my old one does not feel too bad but there are some scratches on the rollers. Fixing the inner bearing if it was a ball would mean removing and replacing the complete torque tube assembly possibly many times as you say Bob and I do not relish that. Unfortunately the only guidelines with the new 5.67/1.0 ratio concern the 'blueing' markings and do not address any installation issues. I can only hope that my approach will put the pinion gear in its correct nominal position ready to be adjusted by the AC bearing housing shims. For Stuart I think if I used the wider race I could not push it into the casing past the current peg position because that would take the pinion gear with it from where it should be...that right?