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rear end dummy

G

garin1

Guest
I probably should know this but I don't.If I raise both rear wheels of the ground with posi-trac and turn one forward,shouldn't the other turn forward:confused

Also, What gear ratio would give a 1.75-1 rotation
between the rear wheels and the drive shaft?
I need help:cry
 
S

SARGE81

Guest
yup. both should turn in the same direction. otherwise i would have a bad feeling that your posi traction clutch pack is inoperative. unless for some ungodly reason your vette came with an "open" differential. which i've never seen yet. As far as your ratio i dunno. The most accurate way of finding out your ratio, is to pull it apart and count out the teeth on the ring and pinion gear. Then do a little math.
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Yep, it is true, we measured it together. Either I have forgotten something here, or we have an unusual situation.

Sorry we missed you at the cruise in. We did not get there until about 7 or 7:15. I don't think many people were haning out past 8:00. The weather was getting pretty cold, especially for the rag top guys.

Did you see the pro street 71 vette? Whoa, it had a very hot small block with 150 hsp shot of NOS. I overheard the owner say "bring on the big block guys". Just looking at the tubbed rear wells and 5 feet worth of rubber in the rear is enough to keep me away. His plate said "UR LUZIN". Then he fired it up. It hit like a dragster. Must be some kind of magic going on in that little mouse motor.

Did the brakes work good all the way home?
 

chuck

Well-known member
Joined
Feb 7, 2001
Messages
193
Location
Tallmadge,Ohio
Corvette
1977 Dark Red Coupe/Buckskin 04 Spiral Gray/Gray
Garin1,the gear ratio can be deterimed by a code that is stamped on the bottom of the carrier.The first two letters in the code are used to identify the ratio.These letters are followed by a four digit code for the month and day and a letter code for the axle assembly plant.Here are the codes for a 68.
Axle code - Ratio- Type
Ak 3:36 Standard
AL 3:08 Posi
AM 3:36 Posi
AN 3:55 Posi
AO 3:70 Posi
AP 4:11 Posi
AS 3:70 Standard
AT 3:08 Heavy Duty
AU 3:36 Heavy Duty
AV 3:08 Posi
AW 3:08 Posi

That is what is listed in the Corvette Parts Interchange Manual
Chuck
 
G

garin1

Guest
Thanks for the info Chuck.

My problem is that when I turn the rear wheel one full revolution
the drive shaft only turns one and three quarter turns.If this is correct than I will need a six speed tranny and at 6500rpm should be able to go 185mph:confused
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Ding, ding, ding, ding, ding,............and the answer is...

I just talked to my good friend that builds rear ends and transmissions. He said this is a common mistake, and he has made it before himself. That is, thinking he found a 1.75:1 rear gear.

The problem here is that the posi unit has seen better days. The fact that one tire goes one way and one the other was the dead ringer. He said that testing the ratio by simply turning the wheel and watching the drive turn won't come up correct because the worn posi is bleeding off into the other axle instead of turning the pinion at the same speed.

Also, with a 1968 car that has had more than one owner, my buddy that builds these gears does not trust the casting numbers anyway. After 32 years, there is no telling what is in these cars.

Alright, mystery solved.
 

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