Built Tranny necessities

[Martin S.]

Seems to me there?s a dual taper roller bearing upgrade to replace the ball bearing. My 65 had its original stock box rebuilt back in 99 and it got one of those roller bearings. It also got the Berg poor mans posi shims. That?s one trans that is completely noise free. Too bad it?s leaked forever oh well. 

[andrewlandon67]

Scat has listed on their website a "Heavy Duty Snap Ring Diff," but without any pictures I can't tell if this is any different from a "Super Diff" sold by anyone else. It sure sounds like the same thing though.

[Bruce]

Same thing.  In fact, the castings of most brands look suspiciously similar.....   (Except McKenzies)
While I think all superdiffs are inferior to the stock diff, at least the Scat diff is machined correctly.  The diameters are right, and they have the oil hole in front of the paddle.

Oil hole by the paddle:
I could never understand why some diff sellers don't put the hole in.  When I asked one, he said it goes on the other side for mid engine sandrails.  Makes sense, right?  Wrong!  The drive side of the ring gear tooth is always the drive side.  IOW, the diff always turns the same way relative to the oil.

[andrewlandon67]

Same thing.  In fact, the castings of most brands look suspiciously similar.....   (Except McKenzies)
While I think all superdiffs are inferior to the stock diff, at least the Scat diff is machined correctly.  The diameters are right, and they have the oil hole in front of the paddle.

Oil hole by the paddle:
I could never understand why some diff sellers don't put the hole in.  When I asked one, he said it goes on the other side for mid engine sandrails.  Makes sense, right?  Wrong!  The drive side of the ring gear tooth is always the drive side.  IOW, the diff always turns the same way relative to the oil.

Interesting... Aside from the aformentioned oiling and machining issues, what makes you say that a superdiff is inferior to a stock one? My experience thus far has been pretty positive, and considering that I blew up two stock diffs withing six months, I'd have to say that mine has held up pretty well thus far! While I don't doubt you saying that they're a consumable, I'd like to know what else there is wrong with them.

[Bruce]

It's the type of cast iron used in the aftermarket SDs, it's no where near as good as what VW used 50 years ago.  If you could get a SD that's the same type of iron as stock, then you'd have something GOOD!

When you blew up two stock diffs, was it the diff housing, or the gears?

[dragvw2180]

In my sons turbo car we have an old SD , has a red oxide coating on it and screw in side gear retainers , never had a problem in 20 years of using it . If it has problems with side gears or spider gears I would look at my clutch and rear suspension very closely. Wheel hop will destroy a transmission very quickly .  I like the early cases , the ones that have a pinion bearing plate with 4 bolts , replace that plate with a C/Moly unit . The later cases have a pinion spanner nut instead of the plate , they may be great but the super fine threads are not superior IMHO . Gusseting a early stock case on the clutch side on the bottom makes a stock case superior to a unmodified Rhino case and that is what I am using on my 450 plus HP turbo car along with a stock 3.88 R/P . The earlier 3.80 first gear was very weak and the later 3.78/2.05 mainshaft will hold up extremely well if your clutch package has just a little slippage in it . Nothing is unbreakable if you try hard enough but with a little common sense you can have a lot of fun without spending a fortune. 

[andrewlandon67]

It's the type of cast iron used in the aftermarket SDs, it's no where near as good as what VW used 50 years ago.  If you could get a SD that's the same type of iron as stock, then you'd have something GOOD!

When you blew up two stock diffs, was it the diff housing, or the gears?

To be entirely fair, it was the gears. I could see the iron being lower quality, VW almost had a fetish for using really good metals in their cars. But yeah, I took more than a few teeth off of the gears in two stock diffs.

[Bruce]

Do you know if they were 11/17 gears or 10/15 gears?
I know one guy who claims that two 10 tooth spiders in a stock diff are stronger than four 11 tooth spiders in a SD.

Going from 11/17 gears to 10/15 is like going from a 10 tooth first gear to a 9 tooth first as far as strength goes.

[andrewlandon67]

Do you know if they were 11/17 gears or 10/15 gears?
I know one guy who claims that two 10 tooth spiders in a stock diff are stronger than four 11 tooth spiders in a SD.

Going from 11/17 gears to 10/15 is like going from a 10 tooth first gear to a 9 tooth first as far as strength goes.

I think they're 11/17s, but I'm not 100% sure as the last time I had it apart was well over 2 years ago. One thing I'm sure of is that I didn't change them when I put the S.D. in it, so I either have been really lucky or they're possibly 10-tooth ones.

[Bruce]

I didn't change them when I put the S.D. .......

When you break some of the gear teeth in a diff, all of the gears should be discarded.

[andrewlandon67]

Well I've decided to just go with a Super Street Plus swingaxle transmission from KCR, substituting a 4.37 R&P for the standard 4.12 and buying some good H. D. forged axles. I'm definitely looking forward to having a proper gearbox in my car instead of a ticking bomb!

[Richierich56]

Well I've decided to just go with a Super Street Plus swingaxle transmission from KCR, substituting a 4.37 R&P for the standard 4.12 and buying some good H. D. forged axles. I'm definitely looking forward to having a proper gearbox in my car instead of a ticking bomb!

Andrew - you have PM

[neil68]

Rancho Pro Comp, 400+ trips down the 1/4-mile, GL5 synthetic, no issues yet, except the typical howling in 4th gear during deceleration