[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]

Rear sway bar mounts

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]

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]

Newer Differential

And here's the newer design

 

[Larry T]

Rear Axle Identification

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)

The 69 that I have has several yet-to-be-identified modification by the previous owner.
The engine was swapped to a 1.9 and the carb to the DGAV. Looking at the brakes, the wheel cylinders on the rear apprear to be the later style (according to OGTS). Trying to verifiy if the entire rear end was swapped, without taking it apart (it's not leaking right now and I don't want to mess with it). I checked for the breather cap but I'm not sure if I found it. If my information is correct, it should be located on the top of the right side axle housing. All I could find there is a small 'nub' sticking up. Is this it? If so, would I be safe in assuming that this is the later model housing?
Thanks.

 

[opelspyder]

No, you have the early rear end. Brake stuff can interchange...just have to use the correct E-brake cable. The later rear end breather is plastic and rather tall compared to the early half round steel breather with a wire in it to keep it clear.
Keith

 

[jlthunder]

One other method is to look at the bolt pattern on each end of the axle. There are four bolts at each end which you can see if you remove the drum and look at the axle. There are 2 holes in the axle between the lug nuts. If you spin it, you will see the holes will aligh with the four bolts.

I forget which one is which, but one, the 4 bolts form a trapazoid, while the other one forms a square.

As far as the brakes, I believe it is due to the way the e-cable attaches to the shoes. The later ones use a stirrup and the early ones use a clip(I think). If you have an early axle, you can change out the e-cable at the adjustment point and switch the cables I believe.

If you have a 1.1 axle, the brakes are different and you need to the axle to handle the increased HP from the 1.9.

 

[GoldGT]

The early axle backing plate bolts are the trapezoid, the later ones are in a square pattern. I'm not sure I would assume that you have an early one based on the type of breather, it is always possible that an early breather was installed into a late axle, unless the hole sizes are different so that doing the switch is not possible, which I do not know.

 

[hrcollinsjr]

I'm not sure I would assume that you have an early one based on the type of breather, it is always possible that an early breather was installed into a late axle, unless the hole sizes are different so that doing the switch is not possible, which I do not know.

I believe the holes are of different sizes, with the plastic vent requiring a larger hole.

The description some parts books use to distinquish the difference between brake shoes is: Folded lever and Hooked lever. The folded lever is the 'earlier' style utilizing an e-cable with a ball on the end. The hooked lever is the 'later' style requiring an e-cable with an 'eye or loop' on the end.

HTH,

Harold

 

[jlthunder]

I believe the holes are of different sizes, with the plastic vent requiring a larger hole.

The description some parts books use to distinquish the difference between brake shoes is: Folded lever and Hooked lever. The folded lever is the 'earlier' style utilizing an e-cable with a ball on the end. The hooked lever is the 'later' style requiring an e-cable with an 'eye or loop' on the end.

HTH,

Harold

If the rest is identical, you can remove the lever from the old shoe and put it on the new shoe.

I got a set of drum brake pads and it didn't come with the lever, so I took it off the old set. I used a bolt with a nut with the nylon ring so it wouldn't loosen, but allowed the lever to move freely.

 

[Larry T]

So, it looks as tho' checking the bolt pattern on the axle ends may be the most reliable without opening the rear end up. I sure appreciate the info. Getting this car has been sorta like an Easter egg hunt....surprises around most every corner:yup:

 

[First opel 1981]

This is as good of a thread as any to ask this question.

I know on the older differentials you can replace a bent backing plate by pulling the axle (removing c-clips and pulling axle out).

On the newer style, to replace a bent backing plate, I know you have to pull the axle but does the bearing have to come off?

I want to know what I'm in for before taking stuff apart.

 

[RallyBob]

This is as good of a thread as any to ask this question.

I know on the older differentials you can replace a bent backing plate by pulling the axle (removing c-clips and pulling axle out).

On the newer style, to replace a bent backing plate, I know you have to pull the axle but does the bearing have to come off?

I want to know what I'm in for before taking stuff apart.

The bearing is pressed onto the axle on a later rear differential. So it comes out with the axle.

 

[tomking]

This is as good of a thread as any to ask this question.

I know on the older differentials you can replace a bent backing plate by pulling the axle (removing c-clips and pulling axle out).

On the newer style, to replace a bent backing plate, I know you have to pull the axle but does the bearing have to come off?

I want to know what I'm in for before taking stuff apart.

Yes. The bearing will come out with the axle and you will have to install new bearing on replacement axle before installing.

 

[hrcollinsjr]

On the newer style, to replace a bent backing plate, I know you have to pull the axle but does the bearing have to come off?

I want to know what I'm in for before taking stuff apart.

The axle with the bearing WILL pass through the backing plate. Replace the backing plate and re-install your axle with the bearing. You may want to replace the outer O-ring on the bearing while it is out, a simple task if you have one on hand.

Harold

P.S. Assuming the backing plate you are referring to is the one that the brake shoes are mounted to.

 

[guyopel]

The backing plate can be removed after you remove the axle and you will need new gaskets on the backing plate, do not loose any shims that may be in the axle housing they adjust your end play. The backing plate will slip over the axle bearing .HTH
John

 

[First opel 1981]

Thanks.

I had a Frain Bart last night.

I'm sitting here looking at a backing plate that came off the differential and then asked the question.
I wake up this morning and my first thought was "Duh, I didn't have to remove the bearing from the axle to get the backing plate I'm looking at".

So, I actually had had the answer staring me in the face but those brain cells went to bed early last night.

It's the retainer that you can't remove without taking the bearing off.

30 years ago I had to replace a wheel bearing and remembered that I had to take the axle back to have the bearing pressed back off and then a "plate" installed that was left off. That plate was the retainer, not the backing plate.

And, if memory serves me, the backing plate is part of the "shim" system? Meaning the backing plate replacement has to be the same thickness as the one removed, right?