Is it wrong that those caps and rear look sexy?!? Wow! Is my rear end going to look like that?

 

Paul, I'm pretty sure yours is the 1330 stock yoke.
Mike

 

Made set of 1350 u-joint clamps for late model stock car and anyone running the Moser slip yoke. Plan on working on u-bolt style caps next.

 

Works of art for sure!

 

Hi Bill,
I talked to Mike today and he is sending what I need to get most options covered on the yoke front. Great job on the frame off work and kudos to bman for helping a corvette brother.
Can't wait to see everything done.
Dave

 

Me too David, thanks. Hope it will be a quick turnaround. Bman was my savior for sure. Can't wait to see what you come up with.

Bill

 

Pictures of cap for heavy duty stub axle.

 

Picture of factory differential cover with clearance for 12 bolt ring gear.

 

Nice!

 

I just got out my 12 bolt kit that has been sitting in the garage for over 10 years. My 30 spline 10 bolt has held up wonderfully, but I am increasing the power from around 500 hp to just over 600 hp on my road racer, so will be moving up to the 12 bolt and a 3.73 ratio.

On the kit I have, I made the mistake of not getting the Posi cage polished and have just started doing that. I figure the sharp edges of the windows are the most important to radius those for strength to eliminate cracking from that weak area. The next would be how to strengthen the area between the cross-shaft holes and the windows with that area being a weak point, so I only slightly radiused the cross-shaft hole and rounded off the window adjacent to those cross-shaft holes to have slightly more radius.

I am confused having never built a rear diff, in that I would have thought the ring gear would just fit down over the Posi unit and the 12 bolts on that would be sufficient to keep it in place, but it looks like it has to be pressed on! Therefore I will probably take that to a shop, that is familiar with the fitting of the ring gear. I would think I would have difficulty aligning the bolt holes and pressing on the gear with my home press, and I don't have a jig that would fit the meat of the ring, and not be on the gear. I also wonder if this is fitted with some lathe work needed, to cut down the posi case diameter. But I won't think so, because that would be taking away meat and steel from the bottom edge of the big window.

I think the kit ring gear I have was designed with the tooth edges beveled for clearance of the diff housing and Toms only sells still a 3.73, a 4.11, and a 4.37 I think. But the differential case and the rear cover still need grinding clearance I would assume. I will fit my gear set in, to see if the case does have to be grinded still. As the old Pepe 12 Bolts (pre- Toms Differential units) had cut the outside of the 12 bolt ring gear about .200 there for clearance and then to mate and match the pinion, they used to take about 3/16 off of the bottom of the pinion gear essentially the shaft is lengthened but the pinion is still the same in overall length. They were grinding out both the diff case and the rear cover, back in the day!

For taking the minimum off, I want to put the ring on the posi and then repeatedly try to fit it in the case to do the minimum grinding for clearance. That means I should use some playdoh or something to know where it is hitting. I don't want the diff case cracking from a too thinned down area.

Also I assume the posi unit was machined for the width of the posi cage to fit the stock Corvette diff case in my kit? Naturally I am using the wider case! I don't see these kits being fitted into an early case from the C2 days. I think it is a must that you move up to the 68-and higher diff cases!

The cap, my kit only supplies one billet one along with either 7/16 bolts or two 1/2 bolts. Naturally I will drill and tap for the 1/2. On your build, doing two caps is interesting. I don't know why the Toms Differential kit only feels one is needed. Maybe the torque from the pinion direction of turning on the ring gear only really pushes the posi in one direction! On their kit, you use the stock cap on the other side! But I might upgrade that stock cap to 1/2 inch also, and call it a day or copy what you have done and make a billet cap for the other side!

The spider gears the OP showed, don't look heat treated??? I heat treated mine, and will do the ring & pinion gears. I know the wear life expectancy is slightly shorter with them heat treated, but they are more bulletproof!

Also back to the spiders, I sourced a higher quality thrust washer for the seat of the spiders to the diff case, choosing to go with some better (I have some 4340 ones) than just whatever steel they provided!

I have an old HD ""actual steel"" Cover (machined) for mine! I don't like the stock cast iron ones, and even the HD cast Covers aren't of the same strength! I did see an aftermarket aluminum unit and I wanted to buy to check out, but feel the steel cover is definitely superior. I just want to check one out and can throw that on one of my other Corvettes. I don't see anyone selling steel rear covers anymore????

Lastly I have multi-link rear suspensions, and adding a ""top link"", so on my halfshafts, I am making retracting or telescoping 1480 units from the Dana-Spicer catalog. I will be running a 6 inch slip yoke in a 3.5 size to 1480 u-joint fork (threaded for a dust seal), and then on the male slip spline side, I will be putting a 3.5 yoke with the 1480 ujt and might try to adopt like 930 Porsche boot axle covers to cover the spline shafts for further corrosion resistance. I am eliminating my halfshafts as suspension components and they will float!!! It will be tight being 1480 parts, I might put the female slip spline on the outboard side, as to not have to cut my battery boxes. As my suspension is set for the halfshafts to be parallel in static, as I get suspension travel up or down, I will have to calculate my available travel of the halfshaft telescoping spline in and out. My shocks are 4" travel, but with a 1" bumper, so they are restricted to 3" inches of total suspension movement. The radius of my control arms running multi-links probably would be about around a 3" of available travel and less if I dial in more rear anti-dive!

On the driveshaft I am 1350 and had to clearance tunnel fiberglass, but on the C2 that this is all going on, I am installing steel body bushings from a 68-70 car! I eliminated the donuts on the rear diff crossshaft, so I have less clearance at the diff yoke than normal. I now, I can look at the yoke from the drivers seat, as that fiberglass is cut open. I also prefer caps on all shafts, as the u-bolts are known to still allow some rocking, and the strength with caps is about 40% more! Moroso sells some, but they are kind of chunky in size, so I might machine the profile down, instead of just a big square chunk of steal. I like the ones you machined in this thread!

 

The spider gears shown are the new powerforged formed gears from Eaton. According to the engineers at Eaton are 30 % stronger than the cut gears. The tooth geometry was changed with the smaller teeth being larger than the old version. I am pretty sure the Tom's kit should have the diff case already machined. Mike is machining mine which makes sense due to him also setting it up. Most say only the left cap is needed but because of the larger thread and physical dimensions of the new cap I believe it will stiffen the housing up. And as one of the guys in my crew pointed out it looks stupid with the stock cap and 1 machined one. The clearance on the housing I roughed in and Mike will finish in a fixture to take out only what is needed to keep as much strength as possible. The cover I cnc machined to a diameter .03 larger than the ring gear. It will be going to Mike to test fit this week so if any adjustments are needed they can be made. I do have another hd cover that is slightly different than the others out there. It will not allow use of the spare tire carrier however. I can post pictures if you would like. The quantities of this cover are very limited at this time.
The vision of a good Billet cover is starting to come into focus for me now. If it happens it will be much beefier than anything that exists today. I like alot of your ideas please feel free to share. My experience with Mike has been we do a better job collaborating then I would do alone.

 

I like your research (spiders) and attention to detail! Two bad there isn't a see thru cover for these types of mods!

I am having a heck of a time with this thread loading to my iPhone! I wanted to go back thru and read who's axles you were using!

What shop does your friend own? Sounds like he is pretty knowledgeable on these!

 

Search for Tracdogg2 on the forum. The results will speak for themselves.

 

Tracdogg2 is doing just one cap on mine as well. At least no one will see it. He is also replacing the spider gears. Wonder if they are the same Eaton ones.

 

I have come across Tracdog over the years and a great knowledgeable guy!

Me not knowing 12 Bolt intervals, I dont know if Toms cut heat treated 1017 side gears are custom for his inner axles or common 12 Bolt stuff?

My Posi case is an Eaton unit! My axles (inner) are 30 spline! Tom also sold 17 spline c-clip is what I have on my Tom's Diff 10 Bolt unit with the KA flanged and billet bolt on yokes! They also have a flanged inner axle in 17 spline for stock rear diffs!

I guess Toms guy I think his name is Joab? Is the guy planning to take over the business! One of my orders for more Corvette stuff was his first Corvette order! He might bring back the really high end stuff, but he needed to learn more about Corvette stuff and most of the problem with supply was their machinist connection was just getting back logged!

 

Are you doing a 10 or 12 bolt? I do believe in the 2nd cap being added but also understand the economics of it. The Tom's spiders or the new formed gears will both serve you well. I meant no disrespect to anyone I was just reflecting on my guys busting my chops.

 

Tom's is transitioning into new owners and from what I have been told nothing will change. Same parts and same service which is great news for all of us. Six months ago it looked like he might retire and the business with him. My axles are Tom's as are the ring and pinion and half shafts. Mike likes to take things to the next level which is what started the conversations about parts. I am just fortunate that it fits into what I do.

 

I see Tom's has those Eaton formed gears in his 12 Bolt section, but not in the Corvette section!Many of those spiders for the standard 12 are 33 spline, but there is a 30 spline also listed which is probably what are in my kit. On the formed gear it says new, and no price but doesn't state the number of splines! In his catalog in the Corvette section he doesn't list the parts individually for the 12 Bolt conversion except for his special order 12 Bolt rings and pinions!

Also because I am also building a 1969 European Formula 2 car, I had that axle ratio in my head and accidentally stated 4.37! That ratio isn't right, he offers also a 4.56! But I could see someone special fitting with machining just about any axle ratio to about 3.08!

I am the type that has to have all of the engineering and specs figured out! I was trying to figure out also first how they measure Flange height!

The 12 Bolt passenger and truck units are
3- series 1.830
4-series 2.175

Corvette 10 bolts
3- series is 1.800
4-series is 2.080

I have a 3-series diff case, main reason for the 3.73 selection!

Armed with all of this info, I could see someone making this conversion themselves, if they are a decent machinist!

Lastly in one of the other threads on this type of stuff, one member states the 12 Bolt was done badly? I honestly don't see how you can do a crappy job. If you polish the posi cage and radius the windows etc, if you clearance the gears, you shim your pinion and then you tune it, how hard could this be! There are instructions on tuning the discs and even a video on line!

The trick is the machining and what needs machining!

PS I can also really see the need to break in the new assembled diff once installed! I would run it up to speed and then let cool, run it up to a higher speed, and let cool, etc

also the gear oil during break in should be chAnged! I could see using a good conventional oil.

 

I dont see a need for the 2nd cap. I build most all my parts Im trying to decide if I should build my axles, paying for a set up on two axles do to the induction hardening cuts in to the reason for making them myself still on the fence.

 

The 2nd cap is easy to justify on the 12 bolt due to the amount of machine work required to do the conversion. Is it absolutely necessary is a matter of opinion. The 30 spline inner axles use flange yokes as do the 31 spline outers. A 10 to 12 set up is very much apples to oranges with the 30 spline ten being the closest. If you go back to the 1st page of this thread you can see the bearing cap surface trued up and widened for the larger cap. With the larger fasteners and much larger contact patch it should brace the housing quite a bit better.Mike should be posting pictures soon showing some of the other work that he does. There are people putting much more power in these cars than they were designed for. Which drives the need to maybe overbuild in some minds. Maybe I should post picture of caps side by side for accurate comparison if Mike does not. I am following your 10 bolt thread with interest.
I have a great deal of respect for what and how you are doing it.
Dave