Dana 20 rear output bearing preload?

I just got my d20 rebuilt with lower gears and finaly today went on a test drive. Makes no noises, but the rear output definately gets warm. Almost too hot to touch. The rest of the t-case and trans are only slightly warm.

I did a complete rebuild including bearings, but it came with no shims to adjust rear output bearing preload. I reused the old and torqued it down. It is not tight, but it felt tighter than I would have expected and I am now worried that maybe its too tight. Or perhaps it just needs to break in. I have maybe 25 miles on it.

I'm surprised because the novak rebuild kit had no shims even though it has new bearings and races. Of course the instructions make no mention of bearing preload at all. Just endplay for the front output. Is it accepted to just reuse the old shims and run it? Or should I pull it out and reshim it? I just remembered I had some old shims laying around.

Anyone else dealt with this before? I'm worried, big trip coming up this sunday.

Kevo

Ps. Still wish I could go to big bear.

 

nut needs to be tightend to 249 ft/lbs.then position a dile indecator to read off of the output shaft. then pry on the shaft back and forth. end play should be 0.001" to 0.003". this is all done in a vise. hope this helps.
oh. this is straight out of my '78 shop manual.

 

Hmmmmm.....

Thats interesting. I am surprised they want to see some "play" in the assembly. I am wondering if they think the t-case getting warm will take up some of that play. If it has play then there would be zero preload.

Hmmmm.......

Kevo

 

yeh, but yet things like a pinion, you measure the drag in inch pounds and your wheel bearings have preload. hmmmmmm indeed. i treat these tsm like they are the holly grail and they have not done me wrong yet.

on a side note, the instructions given for flat towing state to put trany and t-case into nutral and then lock in the hubs. in theory i can see what they are talking about, but i still dont know.

 

The "play" is to allow clearance for expansion of the bearings, shafts, housing, etc. when it heats up. Needs to be shimmed for proper clearance or at best, you'll have a leak when the seal gets wiped out from too much clearance, or at worst the bearings get wiped out and take something with it. By the way, NO rebuild kit for an 18 or 20 transfer case that I've seen comes with preload shims. I have seen some for the 300 come with them though. Nickmil.

 

Well I found the shims I forgot I had. Luckily at work it only takes about 20 minutes to pull the rear output and add a shim. Went ahead and added .005" shim to the pack and torqued it down. Much easier to turn.

Drove it home and it still feels a little warm, but I think I will just live with it and see how it does.

I'm surprised they sell bearing kits and yet no shims to adjust them. You'd think new bearings would require readjustment. Seems silly to have shims for the front and not for the rear. Its like selling an axle gear install kit without shims for adjusting the gears.

Anyhow, thanks for the info. I'll have to file that away for future reference.

Kevo