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clementine

clementine

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Hello FABO.

I got the 67 barracuda to go around the block the other day and had some rubbing from the backing plates to drums. I just shimmed them out to be able to go around the block again to sort out the alignment I did.

I noticed last time I was messing around with assembly of the diff I put the adjuster on the drivers side. Pretty sure that is incorrect.

Also, I dont remember dealing with the famed 'button'.

So friday I am going to take it to the exhaust shop so he can finish it out from the mufflers and that will be the first time since Ive had the car out for more than around the block.

Im feeling like I should at least give the diff a dirty eyeball and maybe trim the backing plates (yes I know I probably have mismatched parts but the wheels stop when I press the brakes.....)

My big questions are.......

Doesn't a cone sure grip get a button and the clutch type does not? or do I have that backwards. Last time I was in there I could swear that I could not see through to the other side so what is a button going to do? Much less how does the adjuster push against the other axle for bearing preload if there is a obstruction. Again, I dont remember being able to see.

How do I tell the difference betwix a cone and a clutch? (apologies for not using search on this one....just a guy....killin birds)

How important is it to have the adjuster on the passenger side?

Ill start with disassembly. I do have a different chunk around here someplace....a 3:23 489 case I believe...

Oh yes....this chunk is a 741 case with a 3:91 and its been narrowed.

Thanks for the help, I don't wanna burn something up if I can help it.
 
Assuming you have the center section on a bench, the cone type sg bolts together from the ring gear side (another series of bolts inside of the ring gear bolts), the clutch style sg bolts together from the opposite side of the ring gear.
I'm not sure on the buttons (I've got a locker in mine) but I THINK the clutch uses a separate button that can be there or not ("not" is definitely an oops), I think the cone type has a fixed button.
I'm SURE that somebody here that knows more than me will chime in.
Edit: the button is there, so that both axles have something to push against for bearing adjustment. If you run "green" bearings, you don't need the button. And it really doesn't matter which side the adjuster is on.
 
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33IMP said:
Assuming you have the center section on a bench, the cone type sg bolts together from the ring gear side (another series of bolts inside of the ring gear bolts), the clutch style sg bolts together from the opposite side of the ring gear.
I'm not sure on the buttons (I've got a locker in mine) but I THINK the clutch uses a separate button that can be there or not ("not" is definitely an oops), I think the cone type has a fixed button.
I'm SURE that somebody here that knows more than me will chime in.
Edit: the button is there, so that both axles have something to push against for bearing adjustment. If you run "green" bearings, you don't need the button. And it really doesn't matter which side the adjuster is on.
Click to expand...
its in the car but Ill be pulling axles soon to take a picture of what im looking at.

Ill measure and report.

I was hoping that someone would say that it doesn't matter which side the adjuster is on and that if I had the opposite side tighten up well then I must have adjustment and send it.
 
I am thinking that the buttons are not there and that is the reason your backing plates are making contact with the drums, because you can not adjust your axles. Never heard of swapping sides with the adjuster. Someone else can correct me.
 
CRUZE 418 said:
I am thinking that the buttons are not there and that is the reason your backing plates are making contact with the drums, because you can not adjust your axles. Never heard of swapping sides with the adjuster. Someone else can correct me.
Click to expand...
I feel ya there, but then how are they tight on both sides?

I need to take this apart and investigate.

Apologies. makin you guys play ouijie board with this.

pictures soon.
 
If you have stock axles and didn’t have a thrust button in there you wouldn’t have been able to tighten the adjuster to get the end play. So if you were able to set the end play without bottoming out the adjuster it’s not likely to be a thrust button issue.

Drums rubbing the backing plates is almost always a mismatch of small bolt pattern and big bolt pattern brakes and axles. The backing plates are specific to the axles, so SBP axles use different backing plates than BBP axles. Redrilled axles have to use the backing plates and brakes to match the original bolt pattern.

Regardless of the cause, grinding the backing plates or drums so they clear is the wrong answer. Brakes are safety equipment, find the problem and fix it.
 
Spending a good amount of cash on a narrowed rear end, custom axles, gears and a limited slip- and then trying to justify half-assing the brakes?? Sorry, but that makes less than zero sense.
What's the first rule in the car hobby?
Make it safe to drive, then pursue modifications.
 
Ill take some pics after Burgermaster!



17199710084181203382797.jpg


1719971074280996509230.jpg
 
Ok. Pumpkin/axles

So there is a metal divider down in the center of that pumpkin. It does have lateral movement as when i touched it with tape measure it moved 1/8"+\-.

The distance to the divider is the same as the distance from the adjuster to the end of axle.
23 5/16"+\-

Note these are not stock length axles as the diff has been narrowed.

Brakes

I feel that shaving 1/8" off the backing plate as it shows wear marks at various "o'clocks", would be putting the shoe in a fine position. Note that the shoe wear marks on the new drum. It is wearing on the drum towards the inside and after shaving it would be more towards the mounting surface aka outside with about 1/2" not being contacted.... on the outside... clear as mud??

20240702_192057.jpg


20240702_192027.jpg


20240702_192139.jpg
 
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72bluNblu said:
If you have stock axles and didn’t have a thrust button in there you wouldn’t have been able to tighten the adjuster to get the end play. So if you were able to set the end play without bottoming out the adjuster it’s not likely to be a thrust button issue.

Drums rubbing the backing plates is almost always a mismatch of small bolt pattern and big bolt pattern brakes and axles. The backing plates are specific to the axles, so SBP axles use different backing plates than BBP axles. Redrilled axles have to use the backing plates and brakes to match the original bolt pattern.

Regardless of the cause, grinding the backing plates or drums so they clear is the wrong answer. Brakes are safety equipment, find the problem and fix it.
Click to expand...
safety is number one for sure. The issues Im dealing with are a narrowed diff that has probably C body axles that have been shortened and re splined....if I were to guess.

So with new drums and hardware and the shoes contacting the drum (all 2") why does it matter if the backing plate gets shaved?

Not trying to be jerky here friend, I am in learning mode.

Edit: the drum braking surface is 3" wide and the shoes are 2" wide. There is full contact.
 
clementine said:
safety is number one for sure. The issues Im dealing with are a narrowed diff that has probably C body axles that have been shortened and re splined....if I were to guess.

So with new drums and hardware and the shoes contacting the drum (all 2") why does it matter if the backing plate gets shaved?

Not trying to be jerky here friend, I am in learning mode.

Edit: the drum braking surface is 3" wide and the shoes are 2" wide. There is full contact.
Click to expand...

See, that was good information to include, C-body brakes being some extra possibility’s. Are your drums 11”? Because if you’ve got 2” wide shoes and 3” wide drums you’ve got a brake hardware mismatch.

11” BBP brakes come in 11x2”, 11x2.5”, and 11x3”. They all use different backing plates, so the backing plate, shoes, and drums all have to match- you can’t use 11x2.5” backing plates with 11x2” shoes and drums etc.

Typically, the drum surface is roughly a 1/2” wider than the shoe it’s intended for. So, a 2” wide shoe would have a drum that’s braking surface is a bit under 2.5” wide. So if you’ve got 11” drums you could just have the wrong shoes or drums for your backing plates. If you’ve got 10” drums and 2” wide shoes, you’ve absolutely got the wrong shoes at least.

Why do you think the backing plate is ok to cut down? That lip serves a purpose. Just because you cover the surface of the shoe with the drum doesn’t mean it’s all going to work as designed.

Nevermind that needing to cut the backing plate means you absolutely have an issue with your axles or brakes. There’s no reason to shave the backing plates if you’ve got all the right parts properly installed.
 
I see.

I have 11x3 drums.

the shoes are 2"

I bet the backing plates are correct for 11" as that lip fits exactly into the groove between the braking surface and outer lip. I could try 11x2 or probably 11x2.5 they would match the shoes on there.

If I got the 2.5" shoes on there, the problem remains as its the axles that determine how close the drum is to the backing plate.

This diff was narrowed by the previous owner, I believe it came with backing plates and I purchased the incorrect drums.

But as I previously stated, the axes would have to be longer......or.....i need to put a button in.

Does the divider in that set of pics make sense? Is that what the button rides against?

Which side recieves the button?

Does it push up against the divider and then the opposing axle pushes against the divider on the other side?

Thanks for the input.

My opening post did lack quite a bit. guilty.
 
clementine said:
I see.

I have 11x3 drums.

the shoes are 2"

I bet the backing plates are correct for 11" as that lip fits exactly into the groove between the braking surface and outer lip. I could try 11x2 or probably 11x2.5 they would match the shoes on there.

If I got the 2.5" shoes on there, the problem remains as its the axles that determine how close the drum is to the backing plate.

This diff was narrowed by the previous owner, I believe it came with backing plates and I purchased the incorrect drums.

But as I previously stated, the axes would have to be longer......or.....i need to put a button in.

Does the divider in that set of pics make sense? Is that what the button rides against?

Which side recieves the button?

Does it push up against the divider and then the opposing axle pushes against the divider on the other side?

Thanks for the input.

My opening post did lack quite a bit. guilty.
Click to expand...

You’re not following.

Each of the 11” backing plates is different. Because the axle flange offset on all the BBP axles is the same, the backing plate offset has to be different for each of the 11x2”, 11x2.5”, and 11x3” brakes. For each 11” backing plate you must have the correct drum to match the offset on the backing plate. So if you have 11x2” backing plates you can’t use 11x2.5” or 11x3” drums, only 11x2” drums will fit.

If you don’t know what backing plates you have, you’ll need to measure them. The backing plate offset can be measured and that number will tell you what backing plates you have so you can buy the correct drums and shoes. This thread has the method to measure the plates and the measurements for the 11x2”, 11x2.5”, and 11x3” drums

Converting rear drum brakes from SBP to BBP
 
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Ok! Thanks for the brake help. @72bluNblu

Any ideas what the shiny metal divider is way down the axle tube that would be dead nuts center of the carrier?

Is that what the thrust button rides up against?

In my head, if i had a thrust button setup, i would be able to see straight through the axle tube.

For reference, both axles are removed in this picture and this is a narrowed axle housing with a 741 case 3:91 gear supposedly a limited slip.

20240702_192027.jpg
 
On a racecar, do whatever you want, I got no advice. But
ON THE STREET
there is no good reason to run 11x3" brakes on the back, cuz yur gonna have to proportion them down severely, to work on an A-body, to prevent a spin on a panic stop.
Even with 295s on the back, and 10x2s, I had to play with WC size to be able to run zero proportioning.
On the street, with 4 same-sized tires, you might be able to run 9"brakes with zero-proportioning. I haven't tried it cuz I NEVER run 4 same-sized tires, lol.
If you insist on continuing down this road, there are better ways to solve this problem, than grinding stuff.
-----------------
For instance, when I had my rear end narrowed, I had the axles shortened a lil extra.
The idea was so that I could center 325/50-15 tires in the factory tubs.
and NO! I could NOT have cut off the perches and moved them over, as the springs were right next to the bearing housings and had nowhere to go.
I installed spacers between the backing plates and the flanges, plus adjusters on both axles; so that I could center the axle in the tubs.
Finally; I welded spacers on the end of my axles, on the inboard ends, to push them out far enough to be centered exactly, and to put the shoes in the right place .......... cuz for 325s there is no margin for error.
That was over 20 years ago.
 
In post 16
It appears to me, that
you are looking at the captured Thrust-block
This block is NOT found on a clutch-type Limited Slip.
It is found in all cone-type Mopar 8.75 Sure Grips. It is captive on the Crosspin and cannot be lost.
But you can take it out and machine the ends off for additional room to push the axles in. However, there is a limit, cuz if you offset it too far in one direction, it will impinge on the Crosspin, making it absorb the thrust in the corners...... instead of the thrust going to the tapered bearings. IDK how long the crosspin would survive.

The thing is that to remove the thrust block, the pumpkin has to be removed and the Crosspin removed. And to figure out how much needs to be taken off, the axles have to be reinstalled, centered, and the space between them measured, to find a dimension for the new T-block......
At that point, if the T-block is too wide, you may as well just take the excess off the axles.
But if the T-block is too narrow, then your axles are too short. As mine where. I opted to just weld spacers onto the ends of my axles. It ain't rocket science. That way all of my many chunks were still interchangeable.
The only thing to worry about is that the cones and side gears still sufficiently engage the splines. In my case there was plenty of room.
 
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Ok....

So this diff has been messed with, (probably to be used for drag racing) as you know, and it appears I have a cone style sure grip that does not utilize a thrust button. OR is it possible the thrust block can turn 90* so I cant see the hole where the button inserts? or, do I have my anatomy incorrect and the thrust block does not house the button.

Next, is it bad to have the end of the axle against the thrust block? It seems if it has not button, that is where it lives. ya? no?

Lastly would be the brakes. I will address the brake situation after I find out if the axles are supposed to, or can (in a street application) ride against the thrust block.

Thank you for your time
 
So back to axle adjustment... What kind of bearings are on the axles??? Green bearings are a sealed bearing set and tapered roller bearing (original) have a set of tapered roller bearings and a race. Post a picture of the axle bearings on the axle if this is greek to you.

Green bearings are not adjustable and don't need adjusters or thrust buttons in the center of the diff.

Roller bearings MUST have functioning adjuster set up and it should be on the passenger side (swap axles side to side). All Sure Grip units, whether clutch or cone style NEED a thrust block (buttons). If you have 2 people you should be able to get on both sides and feel each other pushing the axles back and forth between you. If it is not there (or only one half of the set is there) you may be able to adjust the axle with the adjuster, but the other axle will never be adjusted since they are adjusting against each other.

You need to get this all squared away before you drive the car again and before you can figure out the situation with the brakes.
 
clementine said:
So this diff has been messed with, (probably to be used for drag racing) as you know, and it appears I have a cone style sure grip that does not utilize a thrust button. OR is it possible the thrust block can turn 90* so I cant see the hole where the button inserts? or, do I have my anatomy incorrect and the thrust block does not house the button
Click to expand...
No; the T-block cannot turn, and the shiny ends are made to be working surfaces. I have never seen a worn-out one.

The clutch type has 4 pinions on two crosspins that interlock in the center. This kind has buttons as there is no way that I can see for it to work otherwise. This system allows the clutch actuation mechanism to work independently from the Thrust mechanism.
 
clementine said:
Next, is it bad to have the end of the axle against the thrust block? It seems if it has not button, that is where it lives. ya? no?
Click to expand...
No it's not bad.
This part of the differential only moves when the car is turning. The rest of the time it is rotating at the same speed as the axles. Gear-oil is sufficient to more or less prevent wear.
In fact, the Thrust Block has more surface area than the Thrust Buttons do, by a bunch.
 
clementine said:
Ok....

So this diff has been messed with, (probably to be used for drag racing) as you know, and it appears I have a cone style sure grip that does not utilize a thrust button. OR is it possible the thrust block can turn 90* so I cant see the hole where the button inserts? or, do I have my anatomy incorrect and the thrust block does not house the button.

Next, is it bad to have the end of the axle against the thrust block? It seems if it has not button, that is where it lives. ya? no?

Lastly would be the brakes. I will address the brake situation after I find out if the axles are supposed to, or can (in a street application) ride against the thrust block.

Thank you for your time
Click to expand...

Without knowing what type of differential you have you can’t be certain what you’re looking at. A clutch type has a small thrust button that’s actually two halves connected by a roll pin, so, the area you’d see through is only like an 1/8”. Plus, half the button could be missing if you only look from one side.

The axles ride against the thrust block, that’s how the end play on the factory adjusters is set- against the thrust block.

Regardless of the type of differential you have, if you were able to set the correct end play on the axles then the thrust block is NOT the issue. Since you have an adjuster on there I don’t know why anyone is talking about green bearings, they don’t have an adjuster and the parts don’t interchange. Which side the adjuster is on doesn’t really matter as far as its function setting the end play.

Since it sounds like you got your backing plates without any brake parts, you’ve got no idea what brakes those backing plates are for. If you measure the backing plates as described in the other thread I linked you can figure out if you have the right brake parts.

To me, you need to ID the backing plates for absolutely certain, and ID’ing the diff would also be very beneficial.
 
Ok.

72blunblu gave me the "ah ha" which many of you may find funny. I did not know that the drum braking surface must match because it keeps the shoe from cocking essentially locking up the rear brakes. IE the shoe has no lateral stability. I was thinking...11" backing/11" braking surface....done...not the case.

Ill get to taking this apart and identifying.
 
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