Hello all, it's been a while since I was on the forum, what did I miss?

I'm in the process of rebuilding a 3.54:1 PL final drive unit pulled from a 1995 4.0L XJS that will be going into my 1986 5.3L XJ-S along with a 5 speed Tremec TKX conversion kit. Nearing the end of the teardown this afternoon, a note in the factory manual made my heart sink:

"NOTE: Before commencing assembly, check from reference numbers and letters that pinion and drive gear are a matched pair, mounted in the correct case. The same serial number must be marked on pinion end and outer periphery of drive gear, and a letter and number (e.g. 1H or 2L) stamped on the casing rear face, must be duplicated on the pinion end. If these requirements are not met the unit must be exchanged." Page 180

I have the same serial number marked on the pinion and drive gear (4341 & 4341), but the rear face of the casing is stamped 1Y and the pinion end is either scribed A, 0A, or 1A, very hard to tell but there's no 1Y on the pinion end. I purchased this unit from Jaguar Heaven in Stockton last year and it looks to have never been to bits.

Someone please tell me I didn't buy an $800 paperweight.. I can't make heads or tails as to why the pinion and drive gear must be matched to a specific casing when the pinion and carrier are shimmed to spec anyway.

 

Cant help with diff as I am in the same boat. Installed a tkx over the winter a s have been making due with the 2.88 so far, not great…reverse is brutal. Would love to compare notes on tkx install. I plan on rebuilding factory diff to 3.73 over winter. 1986 xjs.

 

Having just replaced the ring and pinion on my ‘88, and with much experience on axles I can explain what they are referring to- the “1H” or “2L” example given refers to the pinion centerline to ring centerline. The example “1H” would mean the pinion is .001” high compared to design, and “2L” would be .002” low. The idea is to get a gearset and housing with the same deviation.
I do know that working in Jeep dealers for 40 years and literally repairing 100s ofDana 44 axles, that this deviation was never mentioned in the service literature, which might be why it was somewhat trial and error to get a completely quiet replacement gearset ( especially on the aluminum housing 44s in the late 90s era).
My opinion would be to see if the vendor has another gearset and have them photograph it before sending it, if they don’t (or you can’t discern the etched deviance) go with what you have. The Jaguar application is a little more forgiving in noise due to the cage is rubber isolated and the interior deadens the noise (unlike a SUV).

 

Welcome back!
What did you miss?
2,397 posts about overheating V12's
935 posts about V12 ignition issues
1,642 posts about V12 misfires
1 post from a straight six owner asking WHY would anyone buy a V12?!

Nothing to add regarding your unbelievably frustrating issue, but it sounds like you are in good hands.

Glad to hear you drank the cool aid. You will not regret it! seems to me that the 5spd conversion crew are gaining in numbers. When do we get our own sub-forum?

 

Thanks for that info RGK, makes a lot more sense. I wonder then what the 1Y on my casing stands for in that scheme; .001" on the "Y" axis perhaps?

Last night I noticed a chip out of one of the pinion teeth which in combination with the evidently mismatched parts makes a pretty good case for exchanging this unit with Jag Heaven I would think. I'll be giving them a call tomorrow.

 

Is that a new genuine Jaguar gearset? For $800, I would hope so. You can use a regular Dana 44 gearset from any of the aftermarket sources; they require sleeves on the ring gear bolts and a companion flange (GM style). Probably half of what you said you paid. I’ve not done it, but Google it.

 

Well, first off a huge shoutout to Jaguar Heaven in Stockton, CA. They stood behind their product without hesitation and replaced the final drive unit even though I was outside the warranty period. You don't see that much these days.

But this being my first go at rebuilding a differential I already have questions about the new unit.

The gearset has perfect backlash and the bearings all feel smooth when turning by hand at least. The interior and exterior of this unit looks MINT compared to the last one, though I don't know the mileage on it. The previous diff was out of a '95 XJS and this one is out of a '96. However..

It looks like the cross shafts got very hot at some point judging by the discoloration around them on the carrier housing. Is this something I should be worried about if everything else looks okay? Is there anything I should be scrutinizing/checking more closely? Maybe the carrier was heat treated at the factory and I just didn't notice on the last unit I had because it was so filthy? (It looks like the carrier is discolored but not the ends of the cross shafts) I have the rebuild kit so I'm still planning on replacing all bearings, seals, crush sleeves, and LSD clutch discs.

 

I think that discoloration is likely localized heat treating. Nothing to worry about.

 

Second on heat treat. As clean as that is, I think that I would check the rotating torque (after removing output shafts), check the pattern, and if good rebuild the output shafts and run it. Looks like a real low mile unit to me.

 

Yes, it's heat treatment. They all have it.

 

I'm just about ready to start reassembling the 3.54 differential for my manual swap. My order of various shims from SNG Barratt are scheduled to arrive later this week. But as ever, a couple questions have arisen that I haven't been able to find concrete answers for online:

I believe the correct gear oil for this diff (GKN/Salisbury PowerLoc out of a '96 XJS) is synthetic 80w or 90w GL5 with LSD additive? What then is the proper type of bearing grease when reassembling the output shaft assemblies? Some have said that using synthetic bearing grease will contaminate the LSD clutch discs and others say the same thing about petroleum based bearing grease. The factory shop manual doesn't specify what kind of grease, only that the output shaft bearings should be packed before assembly.

Thanks in advance.

Here are some photos after powdercoating & painting:

 

The manual I have says the bearings should be lightly greased. The grease is there simply to provide some lubrication during assembly and until the car is moving fast enough to splash oil on the bearings for the first time movement after reassembly into the car. The bearings are not intended to be packed with grease, instead think of grease as an assembly lube. I would use ordinary chassis grease, conventional or synthetic doesn't really matter.

See the last paragraph of the instructions:

 

Wow, thanks! What version of the manual is that from? I have the paperback '75-'91 factory service manual and the instructions are very similar but not the same. Mine says to tighten the nut until the torque required to turn the output shaft is 4.5-5.5 lbf. in greater than the starting measurement. If it exceeds 6 lbf. in you must replace the crush sleeve, whereas your manual says 20 lbf. in. The paperback doesn't have the "Note" at the end either.

 

The manual is from the 1990 Daimler DS420 service manual. It uses the same differential. I used these instructions to rebuild the diff in my 94 XJS and it worked perfectly the diff is quiet.

Here is the start of the output shaft bearing replacement section: Service Manual AKM9135 Ed.4 (1990) p51-8(m)

 

When I have done them, I followed the Jaguar 4.5-5.5 lb/in over starting rotational torque. Twenty lb/in seems high for the bearing size; that is in carrier and pinion bearing territory. The Jaguar spec and procedure is same across all of their manuals from what I have. I also packed the bearings with wheel bearing grease and have not had an issue. I use the synthetic Valvoline 75W140 with no additional additives with no issues. Just my experience.

 

One thing I’ve found is a real tendency to overthink rear ends.
Just look at the gear pattern then check if it looks like it should( plenty of places to view that ).
If it looks OK fill it with the proper gear lube ( make sure it’s suitable for positraction) and get out on the track and race it. Oops. Most of you guys just drive.
In over 5 decades of racing I’ve never had a junkyard one fail me.