8 3/4 swapped in but....thrust button?

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clementine

clementine

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Hellooooo FABO!

5 yrs ago (maybe 6 now) when I rolled this puppy into garage, I did a mini tub job for the '70s' theme hot rod and wanted a bigger tire out back as I feel these fastback have a big booty and wanted to even out the look with a big tire. I found a already narrowed 8 3/4 with a 3:91 sure grip and it was pretty close on width so thats what im using. (Yes I saved the original A body 3:23 sure grip with brakes and parking cables...) I dont remember a thrust button when I went through this thing. It has stock style bearings. I am getting closer to being able to take it around the block minus glass and interior, I might be able to 'roadkill' it for testing purposes. Since I cant be absolutely sure it has said button, Do the FABO Gods recommend a pulling of chunk, sliding out of axles, and checking for button? If the button doesnt exist, and the axles are butted up against each other.....or very close to each other...whats the fix? I just dont get how that button has any give to it to affect adjustment. the outside bearing have to be tight against the races ya? So I will pull chunk, slide axles back in, and measure space between them to 'cut in' the button? I have snooped around for the answer, but I am not getting the purpose that button provides as far as any adjustment or stability.

Please pardon my ignorance as I know this has been covered.

Thanks fellas!!

My darlin Clem.:)
 
Without the buttons and stock bearings you would never be able to adjust the axle end play. The axles would move in and out.
 
I suggest pulling the axles and looking through the axle housing. If you can see through the other side, you have no button. 2 choices: 1.) Pull center section and put in a button. 2.) Go to green bearings and forget the button.
 
its this puppy ya?
20211130_091034.jpg
 
Ok, stand down until I produce more pictures. Need to get the duster out while not raining and put some miles on her and pump the brakes first . Will report back today hopefully with pics.

Thanks!
 
As stated, the single adjuster adjusts the endplay of both axle bearings because both axle shafts butt up against the solid button in the center.
 
Your picture is correct of the thrust buttons. They are held together by a long roll pin. In your case that roll pin is broken. When the roll pin is broken you run the chance of pulling the button out when you remove an axle.
 
Ok. So as previously mentioned, this axle has been narrowed.

I pulled the 'adjusting' side axle first and shined the light to look for button. No button. I checked endplay of non adjusting axle and it could move a couple of thou, maybe up to 5 thou and seemed as if I kept going it would loosen more. So I am getting my head around how this pre-load on the bearings works. I measured inside axle housing from non adjusting axle (still in place) to mounting flange on the adjusting axle side. It was about 23 1/4". I measured the, pulled out, 'adjuster' axle and it indeed measures 23 1/4" from end to mounting flange. I am assuming the button is there to have less friction between axles. Any reason this setup wont work? If I shorten axles any more I might run a little shy on spline. If I have to have a 'button' for space between axles, can I just use a hardened washer as to not shorten axle?

Thanks for the input fellas.
20211130_102723.jpg
 
I don't think adjusting one axle against the other is a good idea
 
318willrun said:
I don't think adjusting one axle against the other is a good idea
Click to expand...
Agreed, so this button looks to have some 'give' to it as its two pieces that have the ability to spin against itself, creating only about 1/4" of surface drag instead of full face of axle. I guess Ill look at how much axle I have to spare and make a button out of hardened material. Might be able to cut this one i suppose, making it 3/8" in length vs 1 1/4". Hmmmmmmm...Or start the process of measuring up some new axles to account for button. Sigh....the struggle is real man.
 
clementine said:
Agreed, so this button looks to have some 'give' to it as its two pieces that have the ability to spin against itself, creating only about 1/4" of surface drag instead of full face of axle. I guess Ill look at how much axle I have to spare and make a button out of hardened material. Might be able to cut this one i suppose, making it 3/8" in length vs 1 1/4". Hmmmmmmm...Or start the process of measuring up some new axles to account for button. Sigh....the struggle is real man.
Click to expand...
Green bearings may end all the struggles....
 
So this button just is held in by axle pre-load? what happens when the bearings 'set in' a bit? the button would fall out or be off to one side I guess. In an open diff would it have the ability to fly out?

anyway, Ill go look at green bearings. Seems like there are pros and cons to those.
 
Sent Cass at Dr Diff a message....I feel like its pretty much fixed at this point. Im still open to ideas on how to use the tapered bearings.
 
Bad Sport said:
If you have a clutch style suregrip then those buttons are needed with the OEM tappered bearings.
Click to expand...
Ok. so if I have a cone style suregrip I can run tapered bearings without buttons? Please forgive my ignorance on these issues. Ill pull the chunk next to check style. Otherwise Ill just go green.
 
Look with you having a custom housing, your axles are probably not the right length to work with thrust buttons and the axle adjuster. At this point I think Green bearings will make your life a whole easier.
 
^^^ WHAT THIS GUY SAID^^^ On any nonstock narrowed axle, I recommend green type bearings for a reason some don't consider. Besides the reason that it makes finished axle length much less of a PITA to deal with, ball bearings generally have a better go of dealing with any misalignment issues that the housing may have if an end is just a little out of true. You should see what a bent axle housing will do to ride on type axle bearings and shafts. A friend wishing me well picked up an 8.8 Ford with custom Dutchman axles that was in a 1000 hp Third Gen Hemi powered 1974 Duster. It had pretzeled the axle tubes and they ran it until the toe out out on the rear got nearly unmanageable. (I imagine it was howling like a banshee, too!). That is one set of brinelled axles. It took a lot of 48 ounce ball peen and 6 pound sledge hammer action to get that one apart...
 
FWI
for those following along;
When traveling in a straight line with same sized tires, everything inside the diff is rotating together, so NO wear will occur on the buttons or the spacer, or the axle ends. Gear oil is a notoriously slippery substance, and when you add the whale-oil, it only gets more slippery. I have seen 20 year old axles come out with nearly no wear indicated.
With that in mind, when my axles came up a lil short, I just tack-welded a small ordinary washer onto each axle, and set up the end play as per the usual.
Back in the day, I was swapping pumpkins several times every summer sorting my DD out. So those welded washers got lots of inspections. I'm gonna guess that the last inspection mightabin in 2006. I have never since then had to adjust my end-play, so I'm assuming the washers are still doing their jobs.
If you have tapered Timkins, you have to set the end-play to center the bearings and to distribute the load equally among them. When you Hotrod around corners, the weight shifts to the outside wheel and the Timkin becomes a combination load-carrying bearing and a Thrust-bearing. Because they are tapered rollers, they absorb that abuse and come up un-phased about it. But all the rear weight, plus that thrust generated by the turning, is being absorbed by the center spacer, properly called a thrust block, and in my case by the washer. So to prevent them from getting jack-hammered, by my driving style, I set the Endplay tighter than by the book. I keep an eye on it by push-pulling on the body transversely, and listening for the tell-tale, clunk-clunk.
Endplay also changes as the Timkins wear out. I packed mine with black Moly-Grease
So far so good.
 
oldkimmer said:
Looks like he has a cone type suregrip with the block in it. So he should be able to adjust it. Kim
Click to expand...

Thanks for the reply Kim, so you are saying I can adjust it the way it is?? When I measure off the passenger axle, (at least thats what I think Im looking at ((post #10 pic))) its the same measurement I get when I measure from adjuster flange to tip of drivers axle. The diff came from a well known guy in the area, but it was one of his early diffs, so it might have been strictly set up from drag racing. Not sure of that info, just guessing.
 
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