Kadett 3.18:1 Differential on a GT?

[kwilford]

I happened to come into a factory rear sway bar and matching differential from a '69 Kadett wagon. I already have an ADDCO sway bar set (front is 19 mm or 3/4 inch, and rear is 16.6 mm or a bit thicker than 5/8 inch), which works fabulously. But my Calgary friend John doesn't have one on his '71 GT, and I wondered if the Kadett bar would:

1) fit a GT? It looks like it would.

2) improve his GT's handling (it is only 13.6 mm or 0.536 inches, compared to my 5/8 bar and the 3/4 inch bar that OGTS sells)?

3) if yes to both, what bracket should he use? OGTS sells one, or he could grind off the old bracket from the donor differential housing and weld it on his? (He has the newer post '70 diff with the outboard axle retainers, which is a better choice than the Kadetts floating axle design and obsolete bearings and seals)

4) Does he need a front sway bar immediately (I suspect the rear bar alone will induce a bit of oversteer)?

Thanks!

[davegt27]

1) fit a GT? It looks like it would.

yep it will fit

2) improve his GT's handling (it is only 13.6 mm or 0.536 inches, compared to my 5/8 bar and the 3/4 inch bar that OGTS sells)?


yes it will improve the handling and more importantly it will help locate the rear end --- (save that barrel spline)

3) If yes to both, what bracket should he use?

The Bracket that OGTS sells is a copy of the stock ones on the
69 also this will give him the option to upgrade to the OGTS
Bar later.

3b)(He has the newer post '70 diff with the outboard axle retainers, which is a better choice than the Kadetts floating axle design and obsolete bearings and seals)
you mean the inboard "C" clips as for which is a better choice
if there is nothing wrong with the early rear end its just as good as the older

4) Does he need a front sway bar immediately (I suspect the rear bar alone will induce a bit of oversteer)?


nope you don't need a front sway bar right away

i did this until i could install a front sway bar just be careful

the early rear will last for years if taken care of the only problem is replacement parts and a friend of mine rebuilt one (some years back 94 or 95) and was able to replace all the bearings but one

HTH
Davegt74

[kwilford]

Thanks Dave. I just have a couple of questions.

What is the "barrel spline" that you refer to? Is it the spline on the torque tube inner drive shaft where it connects to the differential assembly? If so, will the rear sway bar help it out in some way? The sway bar doesn't look like it would do much to locate the rear end, aside from reducing the rotation of the body and hence torque tube rotation relative to the diff housing.

I thought I had read that the outboard seals and some bearings are no longer available for the older "C-Clip" style rear end. Bearings aren't a big concern, but I presume seals are. Although I DO see outboard seals for the early differential on the OGTS web site catalogue, but the paper backing plate gasket is discontinued . I presume that the newer internals are NOT interchangeable into the older housings, are they? Or new-style axles and retainers into the old differential?

It would probably be easier to swap rear ends than weld on the new brackets, but not if the seals aren't available. Is the differential cover the same? The Pick-Your-Part folks (geniuses that they are) didn't realize that the bottom cover bolt is also the drain, so they punched a couple of holes in the cover to drain the oil. Yeesh!

On the topic of outboard seals, I see that OGTS has a separate seal and a bearing shown for the later differential. But when I replaced my outboard bearings years ago, I thought the seal was integral to the bearing in the later models. And the spare set I have looks the same way. Or is the seal they refer to merely the O-ring that helps seal the bearing to the housing? Any insight?

Thanks again for your help.

[davegt27]

What is the "barrel spline" that you refer to? Is it the spline on the torque tube inner drive shaft where it connects to the differential assembly? If so, will the rear sway bar help it out in some way

yep that's it, the Torque tube shaft is called the Barrel spline extension.
i had to replace mine after i started autocrossing.
the body can really rotate a lot in relation to the rear end so adding a rear sway bar is a good idea

I thought I had read that the outboard seals and some bearings are no longer available for the older "C-Clip" style rear end.

i think if you go do to NAPA and ask for 69 GT axle bearings you might not have to much luck but if you go to a bearing place and say give me one like this you might have better luck

as for seal or the paper gasket on the end you could use RTV to seal it up

the older axles don't have a "O"- ring if i remember right

I presume that the newer internals are NOT interchangeable into the older housings, are they? Or new-style axles and retainers into the old differential?

I don't Know this one. I have a 68 Rally rear in one of my GT's it has 3.67 gears and there was some talk about them (ring and pinion) being interchangeable if you added a spacer on the ring gear.
the rest I don't know--except the outer axle bearings for sure are different.

It would probably be easier to swap rear ends than weld on the new brackets, but not if the seals aren't available. Is the differential cover the same?

i bought my Rear end for $50 and Gil wanted $90 for the brackets
plus i got 3.67 gears.
this is a good idea only if the rear end is good
if it is good it will probably last for years

I want to say the rear covers are the same it been awhile
the drain plug was different and the little tab that holes the brake line was in the wrong place
my stuff is in storage in TX and i have seen the bottom of that GT in three years

Or is the seal they refer to merely the O-ring that helps seal the bearing to the housing? Any insight?

yep years ago (i did not know better at the time) i tore the O-ring and the only way to get another one was to buy the hole bearing (same as some Toyota they told me buy the way)

i remember talking to Gil about it on the phone and thank God he added it to his parts list
it was $10 last time i checked but the bearing was anywhere from $45 to $70

I should mention that Gil of OGTS is very responsive to the customers needs
and when he supplies a part it going to be exactly the right size

HTH


Davegt74

[RallyBob]

Just a note: The early GT/Kadett axle bearings are not available even from a bearing supply house. They were specifically an Opel item, they don't crossover to anything else. Neither FAG or SKF(OEM suppliers) make them here or in Europe anymore.

Those early rear axles are more prone to failure too, the bearings ride directly on the axle shaft...low gear lube = failed wheel bearings AND a ruined axle shaft. Later axle shafts are not affected by this.

But anyway, it is easy to weld on those swaybar brackets to the later axles, and it's worthwhile IMO since all the parts are obtainable and the axle bearings are a little stronger. That, and disassembly is easier due to lack of c-clips on later axles, and limited slips can be fitted to the later axles. Early rear axles had special limited slips for use with c-slips that are no longer available.

[kwilford]

I've copied this thread to the "Drivetrain" section, since that is the direction it has taken.

And to take it further, I have some questions for the gearheads in the group.

So, this Kadett differential is from a '69 wagon, has the old style "C" clip inner retainers, and has the brackets for the factory sway bar intact, and I have the factory rear sway bar. The outer bearings and internal gears seem to be good, and there has only been slight leakage on one outer seal, which is available from OGTS.

The interesting part is that it is the 35/11 (3.18:1) gear ratio, compared to the stock GT's 3.44:1. So it is kind of like an overdrive, in the order of 8%. Which means that instead of 3500 rpm at 70 mph (113 km/h for my fellow Canadians) the engine would turn over at 3235 rpm. Not quite as slow as fifth gear with a Getrag (0.804:1), at 2814 rpm, but it would still better than the screaming the poor CIH makes at highway speed. At the expense of some standing start acceleration, but GT's with 1.9 low compression engines are hardly drag racers!

So here are my questions:

1) Should I just use the complete Kadett rear end, and if so, which transmission would it be better suited to:

a) My stock 4-speed, for the reduction in cruising rpm? Or

b) John's (soon to be) Getrag, which has a lower (stump-puller) first gear, which has an 8% higher ratio, and who really needs the sway bar?


2) One choice, to avoid welding sway bar brackets on a new-style housing, might be to use the old-style housing and new-style internals. Are the components interchangeable between the old and new style rear end. Specifically, can I use John's new-style axle shafts, complete with retainers and sealed bearings, in the old rear end housing with the old differential? The housings "look" the same, but I suspect that the place where the outer bearing sits in the housing is somehow different. Or does the old bearing outer race have the same outer diameter as the new-style bearing?

3) Or, if it makes more sense to use the lower ratio gear set with my 4-speed, can I use the Kadett differential in my housing with my axles? Will the new-style axle splines fit the old differential, and does it matter that the axle would be held in place by the outer retainer rather than by an internal C-clip? If not, how about just swapping the ring gear and pinion? Anyone tried this?

4) Am I making this too damn complicated? Should I just tell John to order the sway bar brackets from OGTS for his own rear end, and send this (intriguing but space consuming) Kadett rear end to the crusher? Or should I pull the axles and outer bearings first, assuming that they may have value to someone in the Opel community?

I guess I could disassemble both my '71 GT rear end and this Kadett rear end and answer my own questions. But I thought, heck, someone else MUST HAVE run across this before. But one way or the other, one rear end MUST GO!! I just don't have space to start accumulating spare parts for cars I don't even own!

[opelspyder]

What about suggesting a rear end from a GT with the factory sway bar mounts already there???? Just no sway bar? How rare are these? I have one that came out of a 72 model gt and I'm certain it is original cause it is a later rear end. Has plastic breather tube on top right shaft housing. New bearings and etc. What is this worth? Also we should mention that a benifit with the later rear ends is that you can do the impulse rear disc brake setup with them

Keith
Tennessee
Opel
Club

[RallyBob]

Keith, the early and late axle housings are different. Bearing size plays the part here, the ends of the axle tubes are different diameters and depths.

You can swap the 3.18 gear set into a later axle no problem, the ring and pinion will bolt to the 3.44 carrier. Bearings at the center section interchange.

Bob