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Topic: rear differential swap

in Forum: C3 Driveline Components

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rear differential swap (1/10)
5/10/05 4:32am

Stingray406SB

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Bismarck, ND - USA

Vette(s):
1970 stingray, t-top, mulsanne blue with black interior, 406 ci with 444 hp, racing suspension, hooker headers/sidepipes - SOLD :(

Joined: 10/1/2004
Posts: 380

found me a store selling an eaton posi differential for 63/79 corvette...

applications: GM Corvette: 1963-1979; 10 bolt; 8.20 ring gear, 17 T spline axles, 4.11-4.56 gear ratio.

when I replace the tranny in the vette, I want to swap the rear differential for 4.11's...my question is can I take off the stock 3.08s and swap this unit onto the car, or would there be some reason it wouldn't fit (namely, I don't understand the numbers given for ring gears and spline axles and so don't know if I can just swap em out).

I'd appreciate some help.

______________

Mike

My old Stingray...sure do miss it:

(click image to see a bigger version)

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rear differential swap (2/10)
5/10/05 7:08am

smoke-m
Former Member
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baytown, TX - USA

Vette(s):
1979 maui blue/doe skin, fuel injected 383, 6-speed manual, hooker sidepipes, 3.90 gear

Joined: 4/21/2004
Posts: 160

The carrage that your ring gear bolts up to is good up to 3.90 gears.A change to 4.11's will require a carrage change as well.

rear differential swap (3/10)
5/10/05 3:02pm

Stingray406SB

yeah...the store emailed me back and apparently the unit sold is just the Eaton Posi unit...I would need to supply ring and pinion, bearings, shims, etc...so it's not just a swap. I need a unit where everything is included, and unfortunately, I don't have the thousand dollars to spend on that right now.

______________

Mike

My old Stingray...sure do miss it:

(click image to see a bigger version)

rear differential swap (4/10)
5/11/05 9:22am

Stingray406SB

alright, so since that Eaton thing required me to buy additional parts...I'm looking at this.

A FACTORY ORIGINAL GM REBUILT 411 POSITRACTION REAR CENTER SECTION(COMPLETE) FROM A 69 VETTE.

Once again, I know nothing about differentials, and the seller hasn't gotten back to me yet...is this the entire unit or would I need to buy more parts?

http://www.C3VR.com/member_pages/6601_6700/6623/56613Dsc0155 5.jpg

http://www.C3VR.com/member_pages/6601_6700/6623/56613Dsc0155 8.jpg

http://www.C3VR.com/member_pages/6601_6700/6623/56613Dsc0155 9.jpg

______________

Mike

My old Stingray...sure do miss it:

(click image to see a bigger version)

rear differential swap (5/10)
5/11/05 11:33am

kstyer

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CUYAHOGA FALLS, OH - USA

Vette(s):
1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!

Joined: 12/2/2003
Posts: 6424

It looks complete from your pictures. kstyer38483.4821296296

rear differential swap (6/10)
5/12/05 1:27pm

Van Steel
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Clearwater, FL - USA

Vette(s):
...

Joined: 2/8/2005
Posts: 67

[QUOTE=smoke-m]The carrage that your ring gear bolts up to is good up to 3.90 gears.A change to 4.11's will require a carrage change as well. [/QUOTE]

This is not correct. You can buy a thick 4:11 gear that will bolt up to your 3 series posi carrier. Your supplier should be able to get this gear for you. If he can't, call me up and I'll get one for you. 800-418-5397

Dan

rear differential swap (7/10)
5/14/05 12:54am

custom76
Former Member
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Naples, FL - USA

Vette(s):
1976 coupe with a custom body and a 396 big block with nitrous installed. Runs great!!

Joined: 2/26/2005
Posts: 133

FYI. Don't mean to scare you off but the 4:11 gears will make your highway experience a rather high and winny one. I just hope you don't mind the (greatly)inceased rpm's at highway speeds (from a 3:08). Great for boiling hides but a more street friendly ratio's would be 3:55-3:90. These still have a good amount of low end grunt and you will be happier with the gas mileage and drivetrain wear.
Phil

rear differential swap (8/10)
5/15/05 2:59am

Stingray406SB

[QUOTE=custom76] FYI. Don't mean to scare you off but the 4:11 gears will make your highway experience a rather high and winny one. I just hope you don't mind the (greatly)inceased rpm's at highway speeds (from a 3:08). Great for boiling hides but a more street friendly ratio's would be 3:55-3:90. These still have a good amount of low end grunt and you will be happier with the gas mileage and drivetrain wear.
Phil[/QUOTE]

I'm not too concerned about the highway performance, and hopefully the rpm's won't jump up too high. the 4.11s are going to be used with a 700R4 overdrive transmission, so hopefully it shouldn't be too bad.

______________

Mike

My old Stingray...sure do miss it:

(click image to see a bigger version)

rear differential swap (9/10)
5/15/05 10:42pm

custom76
Former Member
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Naples, FL - USA

Vette(s):
1976 coupe with a custom body and a 396 big block with nitrous installed. Runs great!!

Joined: 2/26/2005
Posts: 133

Yes using a 700r4 will help alot with the cruise rpm. The 700r4 has a overdrive gear of .70. Which means the 4.11 ratio will effectivly be 2.87 in 4th gear.
Here are some gear ratios for different GM trans so you can see the difference in ratios.

Gears.............1st.......2nd....3rd....4th

Power Glide.......1.76......1.0

TH350 ............2.52.....1.52....1.0

TH400.............2.48.....1.48....1.0

700-R4/4L60.......3.06.....1.63....1.0.....70

200-R4............2.74.....1.57....1.0.....67

4L80E.............2.48.....1.48....1.0.....75

Note: Some Powerglides come with a 1.82 1st gear.
Also when installing a 700r4 be sure you have a good trans guy set up the TV cable to the engine. The trans can be damaged if the cable is not set right.
Phil

rear differential swap (10/10)
5/16/05 8:37pm

Van Steel
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Clearwater, FL - USA

Vette(s):
...

Joined: 2/8/2005
Posts: 67

I'm a big fan of the 4:11's. Although it is a bad highway gear there is nothing better(to me) than getting on it and it going. And going quick. 4:11's shouldn't too bad w/the 700r4(RPM wise).

Van Steel38488.8601967593

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