Differential / final drive rebuild

(Steven) #1

Ok, I’m at the point of putting my final drive / differential together. I’ve already run into some problems setting pinion depth and preload. Here we go.

  1. I had no outer shims on my pinion and just 4 inner ones. I measured them with a thimble type micrometer and bought new ones to match.
  2. There was no spacer between bearings
  3. I have a +4 on my pinion, so I set me depth to 2.625+.004=2.629
  4. Left the seals off and torqued output nut to 125 ft/lb.
  5. My preload is really tight. I’d estimate around 40 in/lb just bc the lowest my digital torque wrench goes is 60. Doesn’t feel right, however bearings aren’t lubricated, so not sure.
  6. I used a piece of key bar stock laying on the carrier bolt holes and measured with a standard digital micrometer zeroed out for the thickness of the bar, which is a huge pita btw, and I keep getting numbers around 2.634-2.640. I know this isn’t the exact tool needed, but it’s what I have. There seems like a large potential for user error based on if I’m perpendicular to the bar.

So, any suggestions? Do the outer shims set the preload on the pinion. Seems to me with no outer shims, it should be the loosest setting… Do I worry about getting pinion depth perfect before preload? How much .001 slop is acceptable? Thanks everyone…

(Karl) #2

After going through this for a couple days, I went out and spent a few bucks on a dial indicator and magnetic base. I don’t think I could have done a good job without it.AC_SY400

(MGCJAG S2 2+2) #3

Hi Steven…the inner/outer shims on the pinion are to move the pinio in or out…the crush sleeve sets the pre load…however…depending on the crush sleeve thickness/material /make etc a specific torque could have different results…i assume back in the day when Jaguar wrote the Service manual they knew that a specific troque would crush their spacer by a known amount…i doubt the crush spacer is the same as originals…so ideally you need to go slowly a bit at a time till you achive the required preload …and yes you need you set it exact…Steve

(Steven) #4

So… What the manual refers as the spacer is the crush sleeve? Should I leave it off until my pinion depth is set? Ugh… I have a dial indicator setup like that, but not sure how that helps me set the depth of the pinion. Backlash I can understand, but depth??

(Karl) #5

Pinion depth is a key controller of lash. I set crush collar last.

(MGCJAG S2 2+2) #6

It depends what actual diff you have…there are 3 types…early ones i think use a spacer and shims between the bearings…later use the crush sleeve…basically what your doing for preload is pressing the 2 bearings together on the pinion with something between them…with the crush sleeve the more touque on the nut the more the sleeve crushes pushing the bearings closer together and making them tighter…set pinion depth first…sequance is in the manual…but the manual refers to 3.8 model so probably dosnt include crush sleeve details

(Jack Terrick '66 FHC Greensburg, PA) #7

Brave man! This is the sort of job I leave to the paid professionals.

(Doug) #8

Check out this instructional from Paul C.

1 Like
(Steven) #9

Ok, got it. On to the carrier bearings. Any tips on those? My bearing separator is too small and two jaw puller can’t get in the notches…

(wardell) #10

I made one by grinding up a piece of toolsteel to fit the recess which then fitted into a home made puller. It was clumsy but worked fine.
If you want to email me I can post you the photos which for some reason I can’t upload to this site.
The axle I stripped and repaired 18 months ago was from the xk range, it wasn’t a limited slip diff and didn’t have a crush sleeve.
I also made a pinion preload tester and all the other related tooling and have photos.
I live in York UK.

(Steven) #11

I got the carrier bearings off this morning by cutting the outer race off, then fitting my bearing separator on the top lip, then using some pieces of wood on my press. I’d be interested in seeing the pics of how you were able to measure such a low torque for the pinion bearing preload.

(Terry Sturgeon) #12

I assume that you are going to scrap the carrier bearings so it’s destruction is not of particular concern. I cut the roller cage off and have been able to get a grip on the upper lip with my smaller bearing puller.

(MGCJAG S2 2+2) #13

Your problem will be shimming up the new bearings becaus you will have to fit bearings measure then shim as req which will mean removing bearing…a simple way to measure preload is with fishing type scales…so for example a 1lb pull on a 12in radius from center is 1ft lb

(Steven) #14

Based on the fact that the pinion output flange has around a 2" radius, then it would be about a 2-3 oz pull on a scale, right? I think the setting for pinion preload is around 14 inch / pounds, or 1.4 ft / lbs…

(wardell) #15

Briefly. With the axle on the floor, I got an old wheelbarrow wheel without a tyre and bolted it to the pinion flange. I wrapped a length of old electrical flex around the wheel to give a diameter of about 8 inches. I then fixed a pulley to the garage roof and threaded the cable over it. The cable terminated in a hook onto which I could hang various weights. I worked out the value of the weight which would cause the pinion to turn once the inertia was overcome. Worked great!

(David Langley) #16


If you are calculating a torque value here, this is not the correct answer. Torque is force multiplied by lever length. So to get 14 inch-pounds you need 7 pounds at a lever length of 2 inches. The Service Manual (early type 1 diff) on page H.4 quotes a pinion bearing preload of “8 to 12 lbs/in.” but I think it means “8 to 12 lbs-in.”. Or maybe I need a cup of coffee to clear my head…

(Steven) #17

So, if I fasten a bar so that my radius is 3", then I should be able to hang 4lbs on the end and just get the 12 I’m looking for?

(wardell) #18

I believe this is correct. With my wheelbarrow wheel method I went for a 4 inch radius. A 3lb weight hung on the cable just started to fall which was good enough for me.