rear axle year identification

[flyboytroy99]

Ok so I'm aware that it's to my advantage to install a 71 or later rear axle in my 70 GT due to wheel bearing availability. I have an extra rear end, but how do I identify what year it is?
Thanks for the help once again.

[opelnut10]

Everyone is giving the 69-70 roller bearing a bad rap, I have never seen a bad set. The easiest way to tell if it is a roller bearing or ball bearing rearend is to pull outward on the axle flange if it is a ball bearing axle the axle will move about 1/4-3/8 inch.

[opelspyder]

Look at the breather cap on the passenger side axle tube. Earlier style this was metal-later it was plastic. That is a quick way to sort of narrow it down.
Keith

[flyboytroy99]

Thanks for the info. I'll give it a look.

[jlthunder]

Remove the wheel and brake drum. Look at the 4 bolts which secure the axle to the differential. If it has a trapazoid pattern, it is an earlier axle. If it has a square pattern, it is the later model. You will notice 2 holes in the axle next to the lug nuts. The holes line up the the above mentioned bolts when the axle is rotated. HTH

Jeff

[Tru-Craft]

Originally Posted by opelnut10 Everyone is giving the 69-70 roller bearing a bad rap, I have never seen a bad set.

I agree, the 70 axle is fine. The roller bearings look great, also the roller bearings spread the load over a larger surface area.
Clean everything, put in new seals, synthetic oil and you're good.
Lyle

[tekenaar]

Originally Posted by opelnut10 Everyone is giving the 69-70 roller bearing a bad rap, I have never seen a bad set. The easiest way to tell if it is a roller bearing or ball bearing rearend is to pull outward on the axle flange if it is a ball bearing axle the axle will move about 1/4-3/8 inch.

Hmmmm . . . sounds backwards to me . . . early, "free-floating" axle: roller bearing, clip axle retention; late axle: ball bearing with "interference-fit", solid axle retainer.

Early axle is the one that has 'play' (hence, free-floating) due to clearance for fitting axle retaining clip inside differential . . . thus, roller bearing axle is the one. Ask Rodney about his early axle mishap . . . retaining clip broke, axle walked out of housing!

[opelnut10]

Originally Posted by tekenaar Hmmmm . . . sounds backwards to me . . . early, "free-floating" axle: roller bearing, clip axle retention; late axle: ball bearing with "interference-fit", solid axle retainer. Early axle is the one that has 'play' (hence, free-floating) due to clearance for fitting axle retaining clip inside differential . . . thus, roller bearing axle is the one. Ask Rodney about his early axle mishap . . . retaining clip broke, axle walked out of housing!

Give yourself an atta-boy, you are right I had a senior moment. Funny how you have more of those the older you get, and the longer it has been since you really need to know.

[Dmcbrass]

It's true that the early axle can handle larger radial loads. (cylindrical roller bearing) The disadvantages are:
1. Thrust load, the load created when cornering, is handled by the differential bearings. I'd much rather change a wheel bearing than rebuild a differential.
2. The rollers run on the axle. The Axle is the inner race so to speak. When the bearing fails the axle is nearly always scrap. Even if bearings were available for the early cars, you would still need to have a source for axles. This is the same arrangement that GM used on trucks and vans throughout the 70's, 80's and early 90's. I've changed several axles in their vans for this reason.

[tekenaar]

Originally Posted by opelnut10 Everyone is giving the 69-70 roller bearing a bad rap, I have never seen a bad set. The easiest way to tell if it is a roller bearing or ball bearing rearend is to pull outward on the axle flange if it is a ball bearing axle the axle will move about 1/4-3/8 inch.

. . . I'd be real worried about the axle retaining clip integrity if you can move it that much . . . more like 1/16"-1/8", else brake shoes would end up partially outside of drum! . . . wouldn't do handling any good either with axles sliding back and forth during cornering.

[jeff denton]

When you look at the axle retaining snap ring in the early housing, you can't help but worry about how long that will work. Unless you drive like Grandma...
It isn't even close to the big sturdy C-clip used in a GM diff. Which are really famous for breaking when you drive 'em like Ace Ventura does his blue Monte Carlo .
I like safety so I recommend using the later rear end. It's nice you have a choice!

[Tru-Craft]

Originally Posted by jeff denton When you look at the axle retaining snap ring in the early housing, you can't help but worry about how long that will work. Unless you drive like Grandma...

My 1970 axles have about 1/8" side movement.
Jeff, I agree the later style is better for side load and safer.

I think the reason the clips rarely break, is the GT's rear is light and the tires are small, no traction = no side load. I have 195/60R14 tires on mine, so not much traction, but less traction in the back is fun!!!!
I have been driving like Grandma for over 25 years with those axles!
But, my Grandma can get a car in a 4 wheel drift and bring it back!
Lyle

[baz]

Originally Posted by Tru-Craft My 1970 axles have about 1/8" side movement. Jeff, I agree the later style is better for side load and safer. I think the reason the clips rarely break, is the GT's rear is light and the tires are small, no traction = no side load. I have 195/60R14 tires on mine, so not much traction, but less traction in the back is fun!!!! I have been driving like Grandma for over 25 years with those axles! But, my Grandma can get a car in a 4 wheel drift and bring it back! Lyle

is this right Lyle ? i would have thought 195's would give good traction

back on topic
my gt had the clips in it and i laught my self silly when i realised what i had been doing with the car before i changed to jag running gear

[GTJIM]

I am sure that a smaller 'C'-clip eliminator kit modelled upon a Chevy 10- or 12-bolt diff could be made for an early GT/Opel diff which still has good wheel bearings. The bearings and axles are only ever available 2md hand now - so it pays anyone with this type of diff to think ahead and score a later model one when ever they can - even the late model ones will run out and become real difficult to obtain sooner or later .....

[flyboytroy99]

Well I think I figured out this extra axle is definitely a 71 or later by checking how the e-brake cable attaches. Definitely different than the 1970 I have on the car now. So in the future once the swap is complete, I'll have an older roller bearing rear end laying around for anyone still running one.