Hello, so my lumped S2 kitty is pretty happy with her 3.54 open diff, but I think she'd be even happier with a 3.31 final drive and LSD.
Could the community suggest the best way to get there?
I've searched for 3.31 Powr-lok rear ends but it's near impossible to find anything, let alone in decent shape. Plus I feel bad getting rid of a very clean and perfectly good diff.
I've considered getting Dana 44 3.31 gears and a spline adapter kit but not sure what LSD would be compatible with that set up and the cost is not ideal.

Are there other options that I'm missing? Does anyone know if a rear end out of a later Jag, say an XJS would be a direct fit?

Thanks y'all.
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Just IMO but 3.54 to 3.31 isn't that much change. Will it be worth the effort?

Anyhow, 3.31s are hard to find, yes. I was lucky to find a 3.31 LSD a long time ago. Took a lot of looking. Most have been scooped-up many years ago. It was standard issue on USA V12s in the 70s.

Later came the 2.88 and, in the 90s, the 3.54

A few early 80s cars had a 3.07 ...with LSD if behind a V12

Others here will chime in on using the Dana gears. I can't remember the details but it's doable

Cheers
DD

 

I have a 3:31 for sale that was converted to Auburn Locker. Fully rebuilt and in the car for a short time before I upgraded to 3:73. Located in NYC for pickup or shipping at buyers expense. I'm looking for 900$

 

Thanks Doug, reason I'm considering a 3.31 is because the donor Camaro had a 3.27 final drive so this is close. The other half of it is the LSD. I could have the transmission reprogrammed for a 3.54 final drive but then I still won't be able to make 11s.

 

PM'd!

 

Putting a 3:73 r&p in mine as we speak. Setup is giving me fits and almost to the conclusion it's the new Motive gear set. But if you have an overdrive trans and looking for fun I would go with a 3:73, save yourself the learning curve (it's deep) and get an aftermarket lsd.

 

I put a Motive 3.07 with Auburn Gear locker in mine last winter. Setup pattern and clearances are good, but still whines. Improved a little after awhile, but definitely not quiet. I plan to replace the Motive's with something else this winter.

I chose 3.07's because most of my driving is on the highway. I have enough engine to be respectable and if I need to be respectable quicker, 3rd gear will take me past 100mph which is way faster than Troopers will let you get away with. At 70 in 4th the engine is at 2000rpm and getting 17-19mpg.

Dave

 

Thanks for that info Dave, I have a feeling I'm not going to be happy with this Motive gear, I can't get pattern off the toe when setting backlash. Pinion depth comes in marginal too but prob ok but after getting backlash it's a no go anyway. $250 wasted, I've made about 25 pattern pic folders, the last 12 or so were starting over from scratch and with way too much pinion and then backing off a little at the time to try to sneak up on it Left BL alone exe for enough clearance to rotate, looked good right up until I set backlash. I'm past done with it... Motive is the only gear I know of that's dual drilled for both ring gear bolt sizes.

 

I worked on my pattern and backlash for three days before I thought it looked good, I was probably wrong.
Anyway, the Auburn carrier I'm using (- Summit $426 AUBURN grip-n-lock Carrier AUB-546085 19 spline) dropped right in and you can use any aftermarket Dana 44 R/P you want. It will take different carrier bearings, but they're common items.- Bearings and Races
Carrier Bearings: 25590

Carrier Races: 25523

Pinion Bearing Inner: 31594

Pinion Race Inner: 31520

Pinion Bearing Outer: M88040

Pinion Race Outer: M88010

Spicer 26 spline pinion yoke 2-4-8091X

Input seal is CR 15788 (in Motive shim kit)

Good luck and remember, setting up a differential is like "....a box of chocolates, you never know what you'll get...." until it's back on the road.

Dave

 

I've already refurbed my power lok carrier and am pretty happy with it so after spending nearly $300 on parts for it (part of that learning curve I was talking about) I'll be hard pressed to change that. But I'll be on the hook for another, better quality r&p. I wish I'd bought that Auburn lsd.

BTW... Big Blue, I put a 3:54 in my 71 corvette with an ls1 and T56 and it's a blast, 5th and 6th gear are both overdrives on that trans and with the 3:54 I almost never use 6th.

 

I put the auburn limited slip in mine with the Dana 3/73, but unlike you guys, I admitted defeat after about 6 hours of not getting it right, took it to an off road truck shop and they did it for I think 300 bucks! Could t be happier

 

I've rebuilt the standard Sailsbury on my XJS and the key is getting the pinion depth correct first. If that's not correct, then either the side play or the backlash will be incorrect, you won't be able to get both correct. I had to take my time, but I was able to get everything correct in the end and the diff is quiet.

 

I hear ya' Darren, but trustworthy local vendors are hard for me to find. I've been paying (literally) for poor initial machine work done to my heads all summer. Finally found a small shop that builds drag race cars and engine building in my area. He doesn't advertise so I never came his name. So I've just done everything I can myself, but sometimes I pay for the learning curve as slofut says. Glad to hear you're doing well.

Dave

 

After much research, I think you are spot-on. The Motive gear set I bought did not have a depth setting stamped on the face of the pinion and I didn't have anything to go on. A verbal over the phone from Motive was "...usually x.xxx is a good starting point for the depth and then go from there" and Dana info I could find also gave a generic starting number. I used the original shim pack from the Salisbury pinion as my starting point. When I pull the differential this winter, for the third time, I will know more than I did last winter, so that's a plus.

Dave

 

Point taken Jagboi, that's why this last time I started with only setting the pinion depth and starting with the pinion set deep, that way as I moved it out in increments and taking patterns I could see what it was doing. As I moved past the starting depth of 2.624 (etched into the face of the pinion) it was looking pretty good but still a bit high so I kept going. I think I have room to go one more step before I give in, I'm stubborn, I really hate to let this beat me, I had one pattern where my diff guy said "you could prob run that" but neither of us was really happy with it. Darren, I think I'll prob take your advice if this last try doesn't work out. My diff guy here is the one that everybody uses and he's a good friend, but he's so busy with big stuff I hated to bother him with it.

 

Big Blue, what motor and trans are you running?

 

LS3 and 6L80e, currently with 3.54 open diff.

​​​​​As mentioned, it's not unhappy but at around 85mph it starts wining a bit and I generally expect the tranny to react to downshifts faster. I'm thinking both issues can be rectified with a slightly taller final drive that's closer to what the 6L80 expects since it was programmed for a 3.27 rear end in the donor Camaro SS.

 

Is the rear diff whining at 85mph or are you saying the motor is spinning up a bit fast? I'm on the fence between a T56 and a 6L80e on my car (just for time). Looks like the T56 has much taller 5th and 6th gear overdrives compared to the camaro 6l80e so with the 3:73 I may need to stay with my original plan using the t56. I see now why you may want a slightly taller gear, I sort of took it for granted the overdrive auto boxes would have similar top ratios.
Bill

 

Slight whine, but I want to be cautions about laying the blame solely on the final drive ratio. In my particular case, I think the car has enough power to go a bit taller but by far the bigger motivator to make a change is the lack of the LSD.

You absolutely cannot go wrong with a t56. Would be an absolute blast and maybe something I'd do with another swap.

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It would probably be cheaper to have your PCM tuned for whatever gear ratio you want to use.

Dave