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Rebuilding center differential

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TSi-Rocket

15+ Year Contributor
189
26
Jul 12, 2003
Bryan, Ohio
So I got a new center diff cover machined for the Torrington bearing and a new upper pinion gear from tmz. I had a good housing and spider assembly. I installed new spider shims and assembled the center diff with Torrington bearing and the viscous coupling and snap ring. I ended up with .025" clearance on the upper pinion gear. I put soldier in between the lower pinion gear and oiling washer because I had quite a bit of free play. I used a #7 washer ( .094") and ended up with .150" over all. I cannot find any specs on the net after spending hours searching my manual says as tight as you can get without binding. I think .026" on the upper pinion would be alright but I think I need to close the .056" gap I have on the lower pinion. Does anyone know the specs/clearance/endplay I need. And what sizes are the #1-3 lower pinion oiling washers I have specs for #4-7 washers. Less clearance/freeplay would allow less backlash which seems to be a good thing and would allow a better meshing of the gears, considering the front diff has very little backlash.

thanks

Yes I have been messaging twicks69 in PM but he has been MIA for 4 days and ive already been slamming him with questions, not to mention he's a busy man. I need the right washer and I can finish the car and get it back on the road. I need to clear this car of the garage so I can work on my daily driven awd before winter.
 
I feel like I've been saying this alot lately but contract Jack's transmission. Call or email him, I called him he schooled me and was real nice. I was only counting the teeth on front diff ring gear and wanted to replace anything that might go or if there were any mods I could do while I was in there ( not including major mods). He told me to upgrade that washer to a torrington bearing . Got all the parts from him at good prices too. Might be your best bet, you know he knows his stuff and shouldn't take to long to get a hold of him. When you find out, can you please post the specs? Good luck, you got this.
 
Been talking with twicks69 in private message, I rebuilt with new cap and upper pinion gear with Torrington bearing from him. FSM says .001-.003 on the upper pinion gear. Twicks69 said .007-.008 of clearance overall with the bottom oiling shim installed and the upper pinion shimmed correctly. Having a Torrington bearing machined to fit I didn't have clearance to add one of the upper thrust washers so I ended up ordering a thicker vcu snap ring to take up endplay.
 
I set mine up to be tight but still turn smoothly. Unless you bought a new housing spiders and cross the shit is allready worn enough it doesn't matter. The cd housing get pounded out where the cross rides and lets it get cocked...what does that do to your clearance? I galled 2 of Tim's 4 spider shafts with no reason why, so I went against his advise and smoothed it all up with emery cloth, ground it some oil channels, and added oil scoops like jacks was doing. So far it's survived well. Lots of 6500 rpm launches on qtps.
 
I ground oil passages into the top cover just like the oem one so the upper pinion shaft could get some oil. My dad and I were talking about welding on scoops before I saw jacks thread.. tim advised against it said it would throw the center diff out of balance and cause problems. My dad whos been in maintenance for like 50years said it was too small and too light to be thrown out of balance by a few scoops but I decided against it for now. My cross shaft and spiders were in awesome shape, along with the housing and lower pinion gear... I have 4 center diff on the bench to choose from right now and I checked them all over.. one of them had a bad housing and another 2 had chipped outer teeth. I was however able to take measurements to make sure the one I'm using is in awesome shape.

As far as calling ppl, I work maintenance third shift, its a real pain to try and call ppl during the day when I need to be sleeping.
 
I have scoops on mine. When 3rd gear dies in a few weeks I'll take it apart to see how it looks. I can promise you, that if you play hard with it, it will all be galled to f*** in no time no matter how you shim it.
 
I ended up using a #3 lower pinion oiling shim and having an upper pinion thrust washer surface ground to .020 to get my center diff as tight as I could get while still maintaining easy rotation. I had around .002" of endplay and the snap ring was tight which mitsu says .001-.002" of play for the vcu snap ring.
 
I shimmed to set bearing preloads today. I need to clean, lube and assemble yet. I will use my gopro to take some pictures and will make a video. The camera on my phone sucks maybe I will borrow my wifes s4 to get some decent pictures. I just need to figure out how to post videos on youtube I made videos of most of what I did while working on the trans. I have 4 center diffs in a box right now so either way I will get photo documentation of a center diff rebuild.
 
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