Series 2 diff output shims

Series%202%20diff

Greetings-
Can someone please enlighten me to the procedure for determining the shim thickness needed for #12 in this diagram? I replaced the output shaft seals, and now when I snug up the output shaft assembly to the pumpkin I get some binding in the diff… so I must’ve mixed up some shims…?
thanks!
Bob

You need advice from someone who actually sets up rear ends - specifically Jag types. Just like I can’t recall much of my calculus (despite using it only some 10 years ago in my job!..), I wouldn’t trust my recollection - but I did this job myself. I set my backlash using a dial indicator and the recommended GM yellow “lead”. My ring gear had some run out (a bad thing, but it seems to be very minor.) I think (consult real experts!) you need to remove the cover and redo your backlash as I think the ring is too close to the pinion. I recall not only swapping shims, but buying some new ones. My rear end was worked on at one time and stuff was out of spec to begin with. I THINK swapping shims to restore what you had originally would be false economy - I’d redo the backlash.
However… let’s say you know the rear end was OK and maybe you only had 4 identical shims. If you moved one to the side that moves the ring gear away from the pinion, maybe, maybe all would be good and you’d avoid more major work. This kind of assumes you recall at least a bit about how you took it apart.

My manual says .001-.003" shaft end float on the output shaft w/o a seal installed.
Not really a R&P lash issue, IMHO.
Seek expert advise as the S-2 output flange was a short lived design and not covered in my Bentley SM. You might contact Dick Maury at Coventry West.

The shims on this diff do not control the ring gear position as in the earlier diffs. The shims control the fit of the two pieces of the stub axle bearing retainer to the seal carrier. To loose and it will leak, to tight and it will leak or bend the ears of the housing as it is bolted to the diff. The bearing is a non adjustable unit with ball bearings instead of taper rollers and has not been available for years. The aftermarket one with a bunch more shims to try to make it fit is another botch job. If you have binding, it is probably something not clearanced properly. This was a crappy design and was replaced with a one piece housing unit in the later 70’s until the end of the XJ6/3 - XJS run. The later one will retro fit into the case as an assembled unit.

If you have the tapered roller bearing type (not sure on the ball bearing type), there is shims within the half shaft (item 11 ?..and 9?).

if these shims are not set up with correct endplay/freeplay as specced, the half-shaft will bind once bolted in, it will not rotate by hand,

when I dismantled one like that the bearing inside was blue from heat

The taper roller axles using shims are the earlier style that predate the ones the OP is referring to. Not interchangeable. The later taper roller axles use a crush sleeve.

a call out & big thank you for detailed torque specs you gave me years ago, when I rebuilt my '69 420G diff…its still going strong

Thanks Dick… The 3.54 XJS diff you just re-did for my dad’s Series 3 is working wonderfully.

Back to my problem… I may have picked the wrong picture in my OP…
My unit has tapered roller bearings with shims between them inside the stub axle. This sounds like the “earlier style” you referred to above. Here are some pics. I’m unclear on how to measure or calculate how many shims are necessary.
thx
Bob

The axle pictured is the earlier style. There are two versions of that axle, one with a nut on the outside and the other has the nut on the inside like yours. Both adjust the same. If using new bearings, you want to go for about 1-2 ft/lbs of preload on the bearings. If reusing the bearings, go for ZERO free play once the large nut is tightened. This is a hit or miss procedure as each housing varies slightly. Assemble, check preload torque and either add shims to loosen up or take out shims to tighten. Also, on this style axle, the large shims do control the preload of the carrier bearings as well as the position of the ring gear relative to the pinion. Another hit or miss adjustment. You do want a bit of preload on the carrier bearings if they are new. The gear pattern and back lash will tell you if you need to move one way or the other.

Thanks Dick, makes sense. After changing the seals I got the stub axles back to zero free play no problem by using same internal shims. I am kicking myself over the large shims, I thought I was being careful but apparently not. I must have mixed them up somehow or things would not bind when I tighten the 5 bolts that hold the stub axle housing on. I will go back over my pics and notes. One stack is two .030 shims and the other is one .030 and three what I presume are .003 or .005. Maybe I got the “thick” and “thin” stacks swapped. Regardless I will check pattern and backlash.
thanks again
Bob

Dick, I swapped the shims from side to side (I originally thought the witness marks indicated the two stacks could only have been previously installed one way - incorrect) and everything is back to normal. Clearly I got the left and right stacks mixed up, they varied by about .010. Now I have no binding, good backlash and good pattern. Thanks!
On a related note, is there a spec for acceptable run out on the pinion flange face? How much is too much?
thx
Bob

Optimally, the face needs to have no runout. Any runout that causes the driveshaft to bolt up where it will cycle up and down will cause vibration. Very little runout = very little vibration. A lot = a lot. Hard to tell. How much runout is there?


About .010” when measured like this. The other unit I have measures .002, hence my concern.

Dick, I am thinking I need to pull the pinion flange and true it on the lathe. Any thoughts? Is .010 enough to cause vibration (which I am chasing…)
thx!

Probably not much vibration but every little bit adds up. If you know it is off, now is the time to correct it. Also, get the driveshaft balanced. You cannot get it out with the car together.

Thanks Dick - will true the flange mating surface. We’ve balanced the driveline, tried different drivelines, even tried replacing the rear u-joint with a CV joint and a very expensive custom driveline. We still have a vehicle speed (NOT engine speed) related-vibration at about 65mph that feels like the driveline. Yes, the rear suspension has been in and out over a dozen times with this ordeal. The rear diff is dead silent, so we are not thinking there is anything internal wrong. We have run the car on jackstands with halfshafts out and disks bolted up, still vibrates so not anything related to rolling. Transmission is a 5spd OD from TDM. Trans has been completely rebuilt and is not noisy, so we are not thinking it’s anything in there. We have tried two different exhaust systems. Anyway, we’ll true the flange and go from there. Any other suggestions are welcome, we are very much at wits end with this one. Thanks for the response on the pinion flange, we’ll do that next.
Bob

So when you are running the car on Jackstands, are the wheels off? This would eliminate balance issues with them. If you balance a wheel and only put weights on the inner rim, you can get a imbalance around 50-60 MPH. If no wheels or halfshafts and still a vibration, I would suspect the transmission is touching the body somewhere. Noise will transmit through the body and be amplified. I have seen this numerous times to the point that a professional shop wanted to pull a freshly rebuilt engine to see why it was vibrating so bad. The car also had a 5 speed conversion that was not clearanced properly. Another point to check: does the noise/vibration happen when the engine is revved up in neutral both with the clutch pedal pushed in and let out?

We have run the car with wheels off and even with the half shafts out and just the discs bolted to center section, eliminating wheel, hub carrier, and half-shafts as a source.
The vibration is strictly related to vehicle speed: Gear selected, RPM, clutch in, clutch out, neutral, coasting, acceleration load, deceleration load, none of these seem to change it. It’s strictly tied to vehicle/driveline speed, about 65mph. It sure feels like a classic driveline imbalance, but we have done multiple rebalances on multiple drivelines with no change. The butt-meter puts it at a higher frequency than wheel RPM (and per above we think we’ve eliminated wheels as a source…)
Switched from the rubber rear trans mount that came with the conversion back to a spring-type mount, no change. Pretty sure the trans or engine is not hitting anywhere but will triple check. Very much appreciate this and any other suggestions! BTW it’s a Series III 2+2.
thx
Bob

Yes true up the input flange but also check the axial runout of the driveshaft mounting surface on the flange. A perfectly balanced driveshaft won’t help you if it is off center.

With the clutch pedal pushed in or in neutral, the transmission and driveline are out of the equation which leaves the engine as the problem. I realize you say it is speed related rather than engine RPMs so how does it happen when in neutral and clutch pushed in?