Traction Lock Clutch Shimming

[85pig]

Deep into my 9" traction lock diff rebuild, and found that there are no shims under the clutches.  The clutches look really good, obviously someone has been in there between Ford and me.  The decent friction plates are probably due to not enough preload, so they likely didn't lock up much.

So what I'm trying to figure out is how to set the preload and shim the new clutches without any specialty tools.  I know, I know - I know what Ford says about "100-250ft/lbs", but I have no good way to check that.  I've read different techniques, from putting it together without the preload springs, and checking for drag (too much will chatter, too little won't lock up), I've read not to use the preload springs at all, but rather use extra shims, shim it until you can't turn it on an axle shaft, and back off .005" on the shims (Ford engineers thought it should have preload springs, so I'm not much on that technique).

Anyone have a good, shade-tree way of doing this without some homemade tool from a cut off axle shaft, or something Ford discontinued in 1988?    

[Gary Lewis]

I don’t have any tips. But I assume you’ve read whatever the factory shop manual says, although I’ve not gone to look at what or if it says. However I have a booklet on order that covers the Traction Lock, although I don’t know to what depth. Should be here in a day or two and I’ll see.

[85lebaront2]

I wish I could help you on that, but the only 9" taction lock I had was destined for my 1977 F150, but I sold the truck before it ever got installed.

[mat in tn]

just my opinion and not a quote from any manual. but ford built this to have preload springs. I like the idea of shimming to increase load of the springs just not to eliminate them. the real benefit of a clutched traction loc diff is to NOT lock. there are positive locking units and even spools for those special cases. this unit is intended to give resistance across the diff. enough to "balance" traction and still be comfortable to use every day. yes, it will loosen with age! good oil with friction modifier is a must.

[85pig]

I soaked the plates in modifier and 90w, and assembled it without the springs for the first test I mentioned.  It drags, but after assembling with the springs I can still break it loose by hand.  Too loose, I'd say.  The shims I ordered arrived yesterday, so I may start throwing shims in it, and shim it until I struggle to break it free and turn it by hand. 100-150ft/lbs should be tough to turn, but *just* doable.  250ft/lbs would require "help".  They say you can shim them loose or tight, depending on how you want them to "grab".  For a street/light offroad vehicle, I'm leaning towards looser.  Don't want chattering on corners, and premature wear on the clutches - but don't want an expensive one-legger, either.  

[mat in tn]

find your balance. I usually like them a little tight. normal use for me was crawling around a customers yard trying not to spin while getting the air conditioner as close as possible. or getting the catch trailer in the best spot for the roof tear off. not exactly climbing rocks with three wheels at a time.

[viven44]

Mine is a one-legger for sure ... I did the jack-up rear wheel test and spun one tire and the other spun backwards.

[85pig]

Do you just shim them by feel?  I can do that (and likely will).  I've also read that over-shimming can contribute to the cracked cases that aren't uncommon on these.  

[mat in tn]

are you trying to put one inch of clutches and shims in a 3/4" space? even by feel you should be able to tell before you crack a case. do you have a good dial caliper?

[85pig]

No, no.  I've just read that overdoing the shims can exert excessive stress on the case.  I don't intend to get that carried away.  I just need to see how I can shim it without a bunch of specialty tools.  I'm considering adding about .015 and see how tight the drag is; if it's hard (but not impossible) to turn the carrier on an axle, then I might just run with that, and add shims if necessary (or drop to .010 if too tight).  Not tight enough to chatter on corners, but tight enough to engage both axles when I need it.  What is your method for setting clutch preload?

[mat in tn]

you are about right with barely being able to turn it. but we are all different in what we can turn by hand. I have never been big or strong and getting less grip with age. I like levers! depending on tire size, I don't mind it being on the verge of chatter in tight corners, but they can get loose at the first sign of moisture. I even tried a mini spool in dolly, for about two weeks. loved it then hated it. chattering in corners was just fun. fighting turning on highway was an annoyance. not bad but just enough for it to feel too tight. but when it did a 180 entering my neighborhood without even trying, I realized my wife WILL wreck eventually. now it's just an open diff and btw is my best mpg vehicle.

[85pig]

I guess I'll tighten it up but keep it towards the loose side.  If nothing else it will wear clutches a little slower, but hopefully still lock up when it needs to.