rebuilding and restoring the rear.
After 43 years of owning my 69 L71, I got the window sticker from the original owners daughter and it lists a 4.11 rear. Currently my car has a small block 3.36 rear in it- I knew it was changed when I bought the car in 1977. I picked up this 4.11 at Carlisle this year. Can the case and cover be restored back to stock appearance? I'd like to change the 4.11's to the same 3.36 ratio and it looks like this would be the gear set I'd use. https://www.summitracing.com/parts/etn-esf01884336c Or are there better choices for which brand gear manufacturer?
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Re: rebuilding ans restoring the rear.
Mark-------
In order to install a 3.36:1 gearset in this unit you will have to also change the posi unit. You could use the one out of your existing 3.36:1 unit. In fact, you could transfer both the gears and posi unit from the existing one you have.
The only difference between a small block and big block rear carrier unit is the stub axles. Otherwise, they are the same although some small blocks may have a non-posi differential unit. So, if you were to transfer the stub axles from the pictured unit to the unit you have, you would effectively have what you seek. This assumes that the stub axles in the pictured unit are in good shape and not worn on the inner end. I don't see what you'd be gaining by using the pictured unit except, possibly, the right stamped code and dates.
I have no experience with Eaton gears. However, Eaton is a major manufacturer of differential gears and parts. In fact, they manufactured the differential unit in both of your carriers. U.S. Gear is another quality manufacturer of gear sets for Corvettes.
The unit pictured suffers from some pitting-type corrosion. I know of no way to restore these areas to original appearance.In Appreciation of John Hinckley -
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Re: rebuilding ans restoring the rear.
They were bare iron as mentioned. You can blast and treat it but it will be pitted.
I have not used the Eaton gears, not sure how long they have been on the market but I would use US Gear gears. I would l first check the posi case for cracks. It may change your game plan. Also if it is a 65-69 posi case they are much more prone to cracks forming then the later 72-79's so you might want to think about that as well. If the posi in the current diff is a later one I would use that over the earlier one. US Gear makes the 4 series gears for a 3 series case too so if you want to keep the 336 that is on there you can but if you wanted a 411 it would bolt onto the 3 series case.
Axle endplay comes from 3 areas typically- axle face wear, posi setup, or worn cross shaft holes in the posi case.Comment
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Re: rebuilding ans restoring the rear.
Thanks Gary. I want to remove the 4.11 and install 3.36 gears. Looking at Summit again, the gears I posted are wrong. I need to find a 3.36 gearset that fits a 4 series carrier.Comment
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Re: rebuilding ans restoring the rear.
Mark
The difference between a 3 and 4 series case is the thickness of the flange to offset the thinner 4 series ring gear. 336 will bolt on to either but the gear will not be in the correct position to work on a 4 series case.
US Gear is what I have used for many years and continue to use, although they are now a 2 cut gear. You need a 3 series case, they are out there. A good used 3 series GM/Eaton case is about $100-$200 depending on the seller. A NOS GM/Eaton are up to $600 since GM stopped ordering them about 5 years ago. The current aftermarket eaton is cast in China and assembled in Mexico. It is not a bad case but not as good as the one Eaton made for GM. There are also Knock offs of the Eaton case on the market but I have not used them. I also do not use the internals of the loaded cases. I have the better spiders and clutches and never setup a posi with the spring pack.Comment
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Vice-Chairman (West), Michigan Chapter NCRS
71 "deer modified" coupe
72 5-Star Bowtie / Duntov coupe. https://www.flickr.com/photos/124695...57649252735124
2008 coupe
Available stickers: Engine suffix code, exhaust tips & mufflers, shocks, AIR diverter valve broadcast code.Comment
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Re: rebuilding ans restoring the rear.
My thought as well. Leave the 2 complete assemblies as they are are, drive with the 3.36 ratio. Switch out the stub axles as suggested if you do prefer. Keep the 4.11 ratio as an assembled for future use.
RayComment
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Re: rebuilding ans restoring the rear.
Mark, sticking with the 3.36 is the logical thing to do. But....I love the 4.11s in my L71. Totally uncivilized and outrageous. And forget about highway cruising.1969 Riverside Gold Coupe, L71, 14,000 miles. Top Flight, 2 Star Bowtie.Comment
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Re: rebuilding ans restoring the rear.
Their was a good reason they were changed. With modern cars running under 1500 @ 60 the ultra low gears take some getting used to. Even for short drives it can be a bit much. I would also leave them "as is" if it was me. FYI my 63 was also a 4:11 car. It had GM gears dated 1965 in it when I took it apart. You can see it didn't take someone to long to get tired of the 4:11 ratio. Unless you plan on drag racing I wouldn't change them or if I did it would be to 3:55's. No carrier changed that way.
RickComment
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