Author Topic: C3 diff/axles  (Read 6960 times)

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Offline metalhead

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C3 diff/axles
« on: October 10, 2015, 05:02:48 PM »
So I've been pulling down my rear suspension to fit new bushes and shocks (79 Corvette)... And I have a heap of play in the side yokes on the diff. A bit of reading suggests I'll almost certainly need a diff rebuild and new side yokes. :tears: Anyone had this done and have suggestions as to where to source parts or who to do the diff rebuild? I could probably have a crack at it I suppose, but I haven't rebuilt a diff centre before.

Help?!

Thanks in advance,

Andrew.

Offline metalhead

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Re: C3 diff/axles
« Reply #1 on: October 10, 2015, 05:30:34 PM »
I have .037" play on one side, and .061" on the other. It looks like a lot more!

Offline Bfit

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Re: C3 diff/axles
« Reply #2 on: October 10, 2015, 07:51:09 PM »
If your only using the car on the road and it's not leaking,
Leave it alone .
The spec is 0.004" to 0.008"
A 1/16" ( 0.00625") is quit common
 The play is caused by wear in the clutchs Packs in the diff
Bfit
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Offline metalhead

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Re: C3 diff/axles
« Reply #3 on: October 10, 2015, 08:31:18 PM »
Really? That would be good news! Elsewhere I read anything over. 025" was bad here: http://www.corvetteforum.com/forums/c3-tech-performance/2986941-differential-side-yoke-play.html Also, do you have an extra 0 in your spec figures? Because .061" is a lot more than .008"?

It does leak a bit, doesn't drip but is always covered in oil. I will do some club motorsport (hillclimbs/track days) with it. I thought being effectively the upper control arm that I'd want it as close to 0 as possible?

Offline Bfit

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Re: C3 diff/axles
« Reply #4 on: October 10, 2015, 09:49:35 PM »
Really? That would be good news! Elsewhere I read anything over. 025" was bad here: http://www.corvetteforum.com/forums/c3-tech-performance/2986941-differential-side-yoke-play.html Also, do you have an extra 0 in your spec figures? Because .061" is a lot more than .008"?

It does leak a bit, doesn't drip but is always covered in oil. I will do some club motorsport (hillclimbs/track days) with it. I thought being effectively the upper control arm that I'd want it as close to 0 as possible?

Agree

You don't want the rear steering  you in a direction your not pointing the front.
You cound  drop the rear of the diff down , take the rear cover off and turn the circlips over to see how much reduction you get in end play.
I had 3 mm in one side, when I fitted original shafts to new diff , I had 0.004 and 0.006" end play.
What im saying new shafts won't  fix the problem.
Bfit

Check this out if you want the rear end to work for you .
http://www.ridetech.com/store/1968-1979-c3-corvette-rear-strongarm-system.html
Freedom's just another word for nothin' left to lose
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Offline metalhead

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Re: C3 diff/axles
« Reply #5 on: October 10, 2015, 09:59:56 PM »
Ok, thanks. Might take a look inside the diff, given everything is out anyway. I know the axles themselves aren't the issue, but some things I read said that the side yokes on/in the diff weren't properly hardened in late 70s c3s and are commonly worn resulting in this play? Dunno, will have to open it up and have a look I suppose.

Offline metalhead

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Re: C3 diff/axles
« Reply #6 on: October 10, 2015, 10:20:43 PM »
Just looked at the ridetech link. Are you running it? It's certainly looks like nice gear. The extra space for wider tyres is useful, and the coilovers would offer better tuning ability, along with a better shock location in this instance (located rearward on trailing arm, so will see a greater amount of travel against a given suspension movement). But I find it interesting that the lower arms and trailing arms look very similar in geometry and function to stock, and it still relies on the half shafts for location. Im curious how much actual performance advantage it offers over a good leaf spring, bilstein shocks and good poly bushes etc? I'm interested in your thoughts. Certainly the ridetech setup would allow more and much easier adjustment, and that's a big advantage in itself.

Offline metalhead

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Re: C3 diff/axles
« Reply #7 on: October 11, 2015, 09:31:35 AM »
Doing some math :banghead:, seems even the worse side would result in a camber change of less than 0.25 degrees, which initially doesn't seem a lot, but on the other hand, half a degree change in camber can make a significant difference to handling and/or tyre wear, so...  Dunno.  Anyone done or had done this work before?

Offline Bfit

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Re: C3 diff/axles
« Reply #8 on: October 11, 2015, 07:03:07 PM »
 Yes I run this set up in one of my cars .
And yes the basics are the same  as the original,

The trailing arm is manufactured along the lines of a Webster truss
Deflection in the trailing arm is minimal.
The advantage is in the coil over  being fitted at the optimal angle .
I'll have  something to compare against after the leadfoot Next month.
I'll let you know
 Bfit
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Offline metalhead

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Re: C3 diff/axles
« Reply #9 on: October 11, 2015, 09:46:54 PM »
Cool, I'll be interested to hear!  :drag:

Offline metalhead

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Re: C3 diff/axles
« Reply #10 on: October 13, 2015, 08:10:39 AM »
Has anyone dealt with difftrans in Newcastle? Guy sounded very knowledgable on the phone and said he'd done a couple of these centres before. I'm dropping it off to him today.

For interest sake. Check out the wear on the end of the left side yoke:



Above photo is with the yokes pulled out, below is with them pushed in, you can see the clearance between circlip and plate. Sorry about the blurry picture.


Offline metalhead

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Re: C3 diff/axles
« Reply #11 on: October 13, 2015, 10:13:24 AM »
Doing some math :banghead:, seems even the worse side would result in a camber change of less than 0.25 degrees, which initially doesn't seem a lot, but on the other hand, half a degree change in camber can make a significant difference to handling and/or tyre wear, so...  Dunno.  Anyone done or had done this work before?

Just a note: I made an error in working this out. Actually ~1/2 degree change in camber for my 1.5mm side yoke movement. Not good! Particularly if your strut rod bushings look like this as well...: