Identify Rear Axle

[Propmark]

A quick questions for the Group...

How can you tell which rear axle you have installed? Are there just two design for the GT, 1968-1970 and 1971-1975? Mine has the factory brackets for the rear sway bar. My car is a '69, but I don't know if this is the original axle. Disc. brakes may be in my future.

Thanks in advance.

[opelbits]

Odds are if you have an original swaybar rear end that fits a GT, it is the early one, possibly out of a Kadett.

The other way to tell is to take off the back cover and look at the ends of the axles, early axles have little 'c-clips' that retain the axles in the housing. Later axles use a press on retainer out behind the wheel bearing.

[opelspyder]

Actually if it was out of a 69 it might be from a Kadett, but some early 72 GTs had the rear ends with factory sway bar mounts. A quick way I found to tell is that the early and later rears had a differnt breather cap. The early models had a metal cap. The later was a plastic cylinder shape. Your rear could have been out of a 72 model. That would be the best way maybe to check without taking the rear apart. If you find it is an earlier one from a Kadett, check the gear ratio, you might find you like it better than the GTs ratio. Kadett had several different ratios available.
Keith
(Just sold rear with sway bar mounts on Ebay)

[Propmark]

The reason I'm asking is that the aftermarket rear disc brake kits require the newer (71-75) axle. Why?


Attached is a photo when the rearend was apart several years ago. May not be enough detail to tell which axle it is.

[RallyBob]

Originally posted by Propmark I reason I'm asking is the aftermarket rear disc brake kits require the newer (71-75) axle. Why?

I believe it's because the backing plates for the rear calipers are an integral part of the rear disc package. But the older diff's used a different backing plate, as the axles are retained by the c-clips near the differential, not the outer axle bearings. So they don't interchange. Hence, the rear disc kit won't fit the older axle.

The axle housing itself is different, so no, you can't put the newer axles/bearings into an old housing!

Bob

[kwilford]

The older style differential uses an outer roller bearing without an integral inner race, so that the rollers run directly on the axle shaft. The outer seal is a separate element, that seals around the axle shaft outboard of the outer bearing. Also, the axle shaft is held in place by a circlip at the inner end of the shaft, inside the differential gear set. If you had to remove a circlip after removing the cover to pull the axle, then you have an older style differential. The seals are easy to replace, but the bearings tend to destroy the axle shaft surface that they run on if the oil level gets too low.

The newer style differential uses a shielded bearing with an integral seal and integral races (both inner and outer). The bearing is held in place on the shaft by a pressed-on retainer ring. To remove a shaft, you just remove the four bolts that hold the retaining plate to the differential housing, and use a slide hammer to pull the axle out. If the bearing becomes damaged, it can just be replaced and usually the axle is fine. To replace a leaky seal, however, the entire bearing must be still replaced (the seal is part of the bearing), which requires that the retainer ring be chiseled off, and a new ring (and bearing) be pressed on to the shaft.

As I understand it, the reason that the disk conversion won't work on the older style differential is because it is a "floating" design, in that the axle is allowed to move side to side a bit. The newer axle is "fixed" in place by the outer retainer ring. Since the caliper is "fixed" (unless a floating caliper design is somehow engineered), it can only be used with the newer differential.

Here's a picture of the older differential:

[kwilford]

And here's the newer design