I was wondering what could happen if the backlash in your rearend opens up. I rebuilt mine a few months ago and it has been a bit noisy since then, but lately it seems to be getting worse. I did everything to specs. The backlash was a little on the high end (I believe the spec sheet said .008-.014 and mine was .013) but still within specs. One thing that I didn't do was sand all the shims before installing them. I read that if there are any burrs on the shims, they will be flattened out over time and the backlash will increase as a result. Another thing that is worrying me is that since I don't have a professional shop at my house, I didn't use one of those spreader things to help set the carrier bearing preload. Since this was my first time doing this, I wasn't %100 sure what I was doing. I just kinda kept shoving shims in there until I couldn't fit anymore. Then I moved them from one side to the other to get the backlash correct. Is this the correct (or at least acceptable) method of doing this?

I'm having my rear diff regeared tomorrow and I don't want any surprises. Is incorrect backlash simply a ring and pinion issue? If it is, I don't care because, like I said, I'm getting a new ring and pinion anyway. Secondly, could incorrect carrier bearing preload cause any damage to the bearings or the carrier itself? I'm on a budget so I only bought a minor install kit. My reasoning was that I just installed new carrier bearings a few months ago and shouldn't need them again. I also still have the pinion bearings and crush sleeves and all that good stuff from the major install kit that I did previously. I didn't touch the pinion gear when I did that so I just kept the bearings in case I needed them later. I just don't want the shop to call up and say "Hey, you need new carrier bearings" and for me to pay to have them installed, only to find out later that there was no way for those bearings to be bad.

I'm just a little concerned that I'm gonna end up having to buy more stuff than I planned on. I'm hoping that the increased noise is from a bad pinion bearing or something, but I'm expecting the worst. The way I look at it (or at least the way I want to look at it) is that if I screwed up THAT bad when I rebuilt my rearend, my truck probably wouldn't still move when I pushed the gas.

 

Depending on what's causing the backlash to increase, you'll get the wear pattern shown below.



If you let it go, you'll break teeth off the gears, and you could potentially lock the rear end at speed, resulting in a nasty wreck.

It's entirely a gear issue, so when they install the new ones, it'll be set correctly. If not, take it back & make them get it right.

The carrier bearings should be OK, but you'd only know if you look at them. If they say they're bad, tell them you want to inspect your old ones.

 

Well I got the truck back today and everything seems much happier. In the words of the tech who did the work, my setup was "horrible". Idk, I did the best that I could. I guess I didn't do TOO bad, because it didn't grenade in the 5 months that I drove it (hard) like that. Whatever. I'm just happy that I've got my 4.56s and my rearend doesn't howl at the slightest touch of the gas anymore.

 

mine has howled when I take my foot off the gas ever since i installed mine. And they still work like a charm. Lucky for me I guess.

 

Well you may want to have that checked out. You don't want to have to spend another few hundred bucks on another gear set. Plus the day of work it takes to get everything set up.

 

the spreader thing is a dial indicator. And you are one lucky ****.

 

No,a dial indicator measures the backlash between the gears, and I did use one. What I was referring to is a device that actually pushes the sides of the differential housing apart enough for you to get one or two more shims in there. It makes it much easier to get the proper preload on the carrier bearings.

 

Jiggle brings up a good point. In reading the actual Ford shop manual, as well as instructions from Ford Motorsports, and others, no spreader is needed - you just keep adding shims to set the differential preload, then shift from side to side to get the correct backlash, of course checking mesh with the pinion gear.

I asked a friend of mine who just retired from Ford and he claims that a spreader IS needed to preload the differential carrier bearings on the 9.75" rear end. It begs the question, just how many people use a spreader to open up the case to preload the bearings???

Incidentally, when I called Ford Motorsports to ask them a question about resetting the speedometer on my F-150, whoever I talked to claimed that Motive was making gears for Ford Motorsport. Has anyone else heard that??

Mark

 

I've preloaded carrier bearings with no spreader. It's just a technique.