[pontiacjeff]

Hello everyone. I currently manufacture and sell the only clutch-type, pre-loaded limited slip differential available for GM FWD cars. My Engineered Performance Limited Slip Differential has been in use for 10 years and proven over 100,000 miles, over 500hp on slicks, and raced on asphalt, dirt, and even ICE! The same unit has been used extensively in the transverse mounted RWD Fiero with excellent results!

Some of you know me and my experience with the big P-axle. I have been building and racing the "12-bolt rear with the 10-bolt cover" for 20 years. One thing we all lament is NO aftermarket support for these rearends! I don't even think you can buy new axle bearings anymore! Forget even finding anything but good used axles. And these days, the only limited slips diffs around are 2-series (2.41/2.56) or 2.5-series (2.73/2.92/3.08) Thank goodness for the new 3.55 gears that fit the 2-series carrier (not sure but probably what I call the 2.5-series). Forget finding a 3-series or paying less than $500 for an old used diff.

That's why I have decided to apply my experience with the FWD differentials to the ole P-axle and offer a drop-in limited slip conversion for the STANDARD OPEN differential. It will be a DIY kit that the average guy can install with hand tools in an afternoon. It utilizes sintered bronze clutch discs, CNC-machined and heat-treated preload plates, and application-specific pre-load spring rates (adjustable to suit driving needs!!!)

I am building the first unit right now. The prototype will be in a car by the end of August. This is not a Mickey-Mouse effort. This is a REAL clutch-type, pre-loaded, limited slip assembly that utilizes STOCK OPEN spider gear sets. It will fit ANY 2-, 2.5-, or 3-series OPEN differential and both the early bearing-retainer (65-70) and later c-clip (71-76) differentials, as well as ANY car that uses the P-axle (8.875" 73-75 A-G, Buick and Olds FS wagons, and 8.75" 77-81 Caddy's and 98's, etc.) It functions JUST LIKE A FACTORY LIMITED SLIP (POSI)!!!!

In conjunction with the new 3.55's, this will be an excellent addition to ANY street or race 65-76 FS Pontiac!

Any and all questions or comments are welcome. (Just, please, no flaming

[Ragtop Man]

Holy crap!

News like this is like "tasing my first draft beer, losing my virginity and going into combat" all in about seven seconds.

What is your projected price point? I am sooooooooooooooooo ready for this!

[pontiacjeff]

The end price will be determined by the initial volume of parts manufactured, heat-treating, etc. But my target is in the $400-$500 range. I sell the FWD units for $599, but there is a little more machine work involved. I'll update again later this week, but keep the questions coming!

I also need to gauge interest, so speak up if you think you'd be interested.

[mike nixon]

I'll be interested in on me of these. I'd think this would be a good seller as it can beinstalled with an exhisting carrier and immediately lose the additional setup labor of a complete carrier.

[65WJ]

well I am in the market. my 2.93 needs rebuilt and the left rear axle bearing is bad.

patrick

[jdh421]

Keep up the good work Jeff!

[pontiacjeff]

Is that an order for two from you, Jeff?

[meanolgoat]

Shoot, I'll sign up for a posi unit in my 65. I've made that "run up the hill" in slick conditions "Just to lose traction and have to start over again" one to many times. I'd be keeping the 2.73 gears, they're just so nice on the highway and two lane country roads...

[aronhk_md]

Hmmm.....I saved the posi from a 2.73 posi rear, thinking I'll just shim it and use it with the 3.23 in my GP convertible with the 3 spd toploader.........but its sounding like you may have an easier solution.

[pontiacjeff]

Originally Posted by aronhk_md

Hmmm.....I saved the posi from a 2.73 posi rear, thinking I'll just shim it and use it with the 3.23 in my GP convertible with the 3 spd toploader.........but its sounding like you may have an easier solution.

Yes, Aron, you won't even need to pull the carrier! No shimming or bearing press operations required! Just leave the carrier in the rearend housing! All you'll have to do is slide the axles out part way, remove the spider gears, and install the replacement gears and LSD kit!

I ordered material to make the clutch plates today. I am using my pre-load assembly from the Cadillac TH425 LSD units I sell (it drops right in between the spider gears of the P-axle!). The spring rate will be adjustable depending on street- or race-use. I'll have all the load measurements soon.

[aronhk_md]

Welllllllll........I hate to say it because I can hear the purists screaming now, but.......my GP conv is only one of 2 I have heard of so far with the 3 spd Ford toploader trans, which is a super HD manual trans, and I think I am going to turbo the car.

Rebuild with low compression pistons, good rods and a moderate cam and leave everything else stock and she'll make 400 hp normally aspirated. But add a simple 75mm turbo and that'll be 750 hp at 15 psi running on pump gas with a nice idle.

Just what the doctor ordered to take care of pesky mustangs, camaros and chevelles. No one would ever think the big old boat convertible could move out of its own way. One of your setups might work very well, although my 2.5 carrier as you call it IS free.....lol

[pontiacjeff]

I went to the junkyard yesterday and yanked a unknown ratio rearend from a 68 Catalina. I think it's a 2.56, but I have not confirmed that yet. I did not have a open rearend, only posi units. But I want to document this from start to finish as if it was in a car, so the only way to do it was to start with a complete unit. This rearend will go in my wagon for testing. It now has a mild 400/4speed.

I promised to document this, so here goes...

(Narrator voiceover)

"A good used complete rearend housing was sourced for this project. No stone was left unturned in the search. Literally. Every gravel stone under the car was disturbed as Jeff laid on his back and cursed the day he was born, all in the name of advancing his Pontiac limited slip differential project!"

[aronhk_md]

Definitely not a posi.........it only left behind one track!

[pontiacjeff]

(@Aron) HAHAHA!!! That is so funny. Very true! And it must be a 2.41 bc it took forever for it to get from under there to over here!

[aronhk_md]

I've gotten a good laugh at that now twice....when I wrote it and again now. Take that pic to the race section and post it under a thread entitled, "Can anyone give me advice on how to better traction?".....then in the thread over the picture put, "as you can see by the track its definitely a peg leg, but I want it to go faster!"

[pontiacjeff]

Originally Posted by aronhk_md

I've gotten a good laugh at that now twice....when I wrote it and again now. Take that pic to the race section and post it under a thread entitled, "Can anyone give me advice on how to better traction?".....then in the thread over the picture put, "as you can see by the track its definitely a peg leg, but I want it to go faster!"

Done:

http://forums.maxperformanceinc.com/...68#post4713768

And serving as a comedic link to the real sh*t here.

[68Prix]

I would be interested in one. Pat

[pontiacjeff]

Well, I took apart the diff that was SUPPOSED to provide parts for the first LSD. But, unfortunately, it suffers from one-wheel-itis!

This is what happens when the old P-axle (or any peg-leg) is subjected to repeated high-torque launches! (or just some good old burnouts, donuts, laying wheels, laying drag, gear-drops, hard right turns, 0-60 standing still, etc, etc!!!)

Excessive "differential" speed. When one tire spins waaaaayyy faster than the other, the spider gears gald the pinion shaft:




and the corresponding wear in the spider gear bore:



Compare the one above to a good spider gear:



Here is the factory steel thrust washer, designed to be a wear surface, but NOT designed to carry any load. It's just in there to keep the gear from chewing up the case. The two washers will be replaced by sintered-bronze clutch discs.



The thrust washer goes behind the big side gears. These gears (x2) will be modified and will replace your stock side gears along with a matching pair of spider gears. (NEVER install and run mis-matched side gear- and spider gear-sets!)



A couple views of the 12-bolt Pontiac standard "OPEN" differential:







I will need to disassemble the rearend I bought since these gears are no good. I will be machining this week.

[pontiacjeff]

Oh, I noticed on inspection, this differential case has the number "2" stamped into it. I don't know why, but it might be an assembly mark to help ID the cases as they grabbed them off the parts bin. This has a 2.56 ring gear on it, so it's safe to assume the "2" stands for "2-series". We will need to verify this if you guys start pulling covers and find the same thing!

[pontiacjeff]

well, tonight I did the preliminary fitment of all the parts. It all fits together well. I will photo-document the assembly process once I do a little final machining on the side gears. There is a cast "bump" on the face of the gears that needs to be removed so the pre-load plates will sit flat. The clutches are made, the plates are made. Next I will be fitting springs and setting up installed height with a goal of 50lbs.ft. of break-away torque... equal to the factory "Safe-T-Trac" limited slip differential. I expect this unit to be ready to test by the end of next week!

I'll be installng this rearend in my 66 Wagon for testing. Driving it for 500 miles and tearing it down to inspect.