I considering on redoing the clutches in my 87 Turbo T 10 bolt 8.5 Ltd slip. Anyone done this, and any pointers on what kit to buy. The rear is in generally good shape overall, gear wear and bearings seem decent but I'm starting to get the odd 1 wheel peel crap at the track and it seems quite easy the turn one wheel while holding the other. Did fresh fluid change late last year with posi additive. I was considering this kit from Summit https://www.summitracing.com/int/parts/etn-29426-00s/overview/ Or is that overkill? Seems they have 3 similar kits, and I was assuming the carbon clutches would work best in my case. TIA
If you have the factory posi unit,with the S-style spring,those clutches will not work,AND they are not that great. The correct clutches are available for about $200.00,and include a variety of shims to tune the posi unit properly. They were assembled rather loose from the factory,and relied on that spring to put load on the clutches. Shim the unit correctly and leave the spring out.
Yes Brian, factory limited slip with S spring. If the spring is eliminated, then what is the source of pressure? What would be recommended kit then in your opinion and what would shimming the unit correctly require?
You can buy the correct clutch kits off of Bruce Ponti,or a variety of suppliers. The original GM clutches were discontinued,but Bruce was able to produce new ones. They are the good,knurled steel. Not carbon fiber,polycarbonate,or any of that other cheap junk that comes in the posi units now. By shimmimg the clutches correctly,you are removing the unwanted slop between the side gears and spider gears. This gives you better mesh between the gears,at their stronger points. By removing the spring,this allows the clutches to relax,or disengage while cornering,which also prolongs clutch life,and eliminates any chatter or clutch noise. The side gears and spider gears will push on each other,putting pressure on the clutches,when needed. Tom,from Tom's Differentials has some good videos showing this on YouTube. He also had an article about this,in an early 80's HotRod magazine. You might find that your existing clutches are fine,and you only need to to tune the unit. They were assembled very lazy from the factory,and the spring was stuck in there to make it all work. The downside of the spring is that the clutches are under pressure all of the time,when they don't need to be. If this is primarily for the strip,you could shim it tight AND put the spring in. You might get some tire-chirping around corners though.
Thanks Brian I appreciate the info. Is Bruce on the board here? Or could I possibly get what I need through Tom's differentials. Where are they located? I'm up in Canada so this may present a challenge
I don't think Tom's has them. Some of he restored vendors starting carrying some replacement clutches,but they are not the good ones. I'll get you connected.
I have them clutches for the 10 bolt 8.5 'S' spring posi just PM as stated 200.00 for the set. I bought what Bruce had.
Just an update regarding the kit that I purchased from Bruce. I installed the the recommended kit from Bruce and everything went very well. Shipped and packed very well and Bruce is super as far as communication and support go. I've never replaced clutch packs on a G80 limited slip "S" spring style rear end. If your a DIY type guy and your old posi clutches are getting pretty weak like mine were and don't mind digging in and doing this job, I highly recommend this kit, as it is of high quality.
