The C3 Corvette Heavy Duty 427 Rear Differential Identification and Teardown

Today I'm taking a few minutes to do a minor teardown and inspection on an early C3 Corvette 427 HD rear differential assembly. In this video I give a brief description of the differential unit and how it's constructed, as well as show how to identify the ratio and date code of the gearset.
To see more of my Corvette Tear Down Videos -
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To see more of my Corvette How To Videos -
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#corvettetrivia #c3corvette #corvettehowto #vettesource
Thanks for watching👍

[@Paperbag-om6mh]

I enjoyed todays video

[@VetteSource]

Great, glad to hear you enjoyed it. Thanks for the feedback👍

[@Classifiedreality]

Good stuff...thank you...👨‍🌾👨‍🌾

[@VetteSource]

No problem, happy to do it👍

[@alberthodge631]

very informative thanks

[@VetteSource]

No problem, glad to do it👍.

[@Anthony-qj7qe]

Good video...looking forward to new content on the 72 Vette 👍

[@VetteSource]

Thanks Anthony, will have more content soon👍

[@vikingmike8139]

That ring gear looks to be in excellent shape.

[@VetteSource]

It is actually quite nice. I've set it aside for the restoration of one of my early C3 chrome bumper cars.

[@vikingmike8139]

You know, if it aint' broke, then don't fix it. Those axle gears just need a thorough cleaning, new gasket and gear oil. And maybe scrub the housing and a coat of paint. A lot of times with used parts you get lucky and find a gem like you have there. Cheers!

[@vikingmike8139]

Oh, and perhaps a new pinion seal. Cheers again.

[@VetteSource]

For sure, excellent recommendations. Have a great New Year👍.

[@joevette6290]

Caps were on smallblocks too!! LT-1's and ZR-1's ( 25) had them!!

[@VetteSource]

That is true, thanks for adding👍. I left that tidbit out since so few of them.made it out of the factory😁.

[@crazyantny9161]

3.55 from 1968 with a 427 was extremely common. I had 3 of them

[@VetteSource]

Yea, that definitely seemed to be the gearset of choice on the street.

[@joevette6290]

My 70 LT-1 had those caps and although no one believes me my canadian car was ordered with no options except a mono fm radio but it had a factory M-22 and 4.56! I seen 5 ZR-1's with 4.56 but only one other LT-1 got this option on 70 and unfortunetly it was stolen and no documentation to prove it!!!

[@VetteSource]

Hey Joe, it's very possible your car had the HD caps. The assembly line was never a set in stone operation, so if the car was ordered with M22 and 4.56, it's possible they installed it with an HD carrier.

[@alexaccica957]

Is it common for a 71 that came from factor with a small block 350 to also have the 427 or 454 rear end you shown with the heavy Ubolt clamps? If so I’m in luck added the 496 Stroker years later… good video, thanks.

[@VetteSource]

Hey Alex, it's not very likely since the assembly line workers followed a pretty strict protocol on which parts were installed where. Odds are that the differential in your car was changed out at some point due to a failure of the original unit. You can always check by looking at the number stamped on the bottom of the housing to see what date and axle code is on it.

[@kiesha104]

Will you notice aby play in either side of the diff if the C clips are busted or off ???

[@VetteSource]

Definitely. Once the C clips have snapped, the side yokes will pop in and out and will tend to mushroom as they continue to pound against the inside of the differential, rendering them very difficult to remove.

[@berponteberponte3231]

can you swap a 3:36 for a 3:08 on a small block 350/300h automatic?? Thanks

[@VetteSource]

Sure, that's one of the easier conversions to make. Keep in mind however, that by changing the rear differential to a deeper gear you will throw your speedometer off a bit, so you will need to swap out the drive/driven gears on the transmission output shaft to match up with your given combination.

[@joevette6290]

Would you recommend synthetic or normal 80-90 wt oil?? I heard synthetic loses some viscosity when hot and can cause leakage through old pinion seals??

[@VetteSource]

Hey Joe, I like the traditional oil myself. I have a rebuild differential unit on the bench right now. I may have to look into the synthetic to see what difference it would make.

[@davem6685]

I called Jerry McNeish and he said to go traditional gear oil with posi fluid.

[@randybills3848]

what do you have in the way of rear gears for a 95 i would like to get away from the 259 and get around 345 or something in that range

[@VetteSource]

Randy, you're in luck because Yukon Gear makes a 3.54 gearset with PN # YGD36354T that is made to fit a Dana 36 2 series carrier like what is installed in your car. I would recommend going that route, since trying to source a Dana 44 with factory 3.45's will be a bigger task and more expensive since the manual retransmission differentials are hugely popular. As long as you aren't looking to throw a 3500 stall in the transmission and drag slicks out back, the 2 series carrier should hold up just fine on the street with the deeper gearset.

[@randybills3848]

@@VetteSource thanks so much for the info and no no racing just a little show off stop light to light thanks

[@VetteSource]

No problem, buddy👍

[@chrissmith7669]

I’ve got a ‘79 that came with a TH350! As I understand it these came with Dana 36 rears that are weak compared to the T10’s that came with Dana 44 or even the later 80-82 aluminum with modified Dana 44. I’ll be rebuilding the engine taget around 400hp. Debating how to make sure the rears good for another 40 years

[@VetteSource]

Hey Chris, like you said, the Dana 44 units first appeared in the 80-82 C3 Corvettes, with the Dana 36 installed in the automatic transmission C4's and the Dana 44's in the standard transmission C4's. The Dana 36 had an 7.75-inch ring gear versus the stronger 8.5-inch ring gear of the Dana 44. The C3 rear differential was manufactured for GM by Eaton Gear, and while pretty strong, will tend to self-destruct under repeated abuse or extreme horsepower. Based on your target horsepower you mentioned for your build, I think you would be fine with the sturdier Big Block unit I detailed in the video. They could withstand the horsepower output of the L88, so you shouldn't have any problems.

[@chrissmith7669]

@@VetteSourceThanks , I was thinking about an all aluminum swap if it’s got the better mechanics even if the housing is a bit weaker. I’m not going to do any racing or even slalom stuff. The occasional high speed highway run be the most. I’ve been seeing the composite spring is a much better ride but isn’t a simple bolt on. Saw the composite on a pre 80 needs longer bolts the German TÜV aren’t impressed with.

[@VetteSource]

Gotcha. I think one of the main issues you will have is adapting the aluminum housing of the 80 and up Dana units to the earlier 79 and down Eaton style differential. The Dana units mount in a completely different manner, with a "batwing" configuration. It's workable but require some frame modification.

[@chrissmith7669]

@@VetteSource well that takes the fun out of that.

[@VetteSource]

Yep, that's for sure😁.

[@kevinsiegel4798]

i dont know how you came up with 9x5 = 40, and then coming to the result of .55, but the math worked out somehow. 🤣

[@VetteSource]

Yep, everyone knows 9x5 equals 55🤣. Like I always say, it doesn't matter which path you take through the forest as long as you find your way to the right place👍.

[@cajunroadwarrior]

I have an 82 with a 427 Dart Smallblock. It's making 550hp at the crank. How can I convert the stock rear end to something tougher to handle this kind of power?

[@VetteSource]

There is a solid axle conversion kit for C3's that handle that kind of power. If youre not looking to go that extreme, an upgrade to a Big Block rear differential with stronger half shafts will handle the extra horsepower well.

[@cajunroadwarrior]

@@VetteSource I know Chevy changed the suspension design between the early and late C3's How do I convert it back to the old design?

[@VetteSource]

Paul, you're correct. I completely missed when you mentioned yours was an 82. The good thing is your car had a Dana 44 from the factory, bad news is its an all aluminum case with a very highway gear ratio. I would look into some of the Corvette specialty shops that offer upgrades for that Dana unit with stronger internals and half shafts. I know they're out there, just can't remember the name of them off the top of my head.

[@cajunroadwarrior]

@@VetteSource that high gear is really messing with my engine. I can't drive in overdrive less than 60mph. The cam is far too aggressive to cruise at 1700 rpm. I drop it to third when I'm below 60mph.

[@VetteSource]

Yep, it's a 2.59 ratio if I am remembering correctly, which kills your ability to keep the engine running in the power band.