I have a used 9 bolt posi. I was wondering if the Cones look ok? Let me know what you think. Hopefully the pictures are good enough.

 

Sorry, your pictures aren't good enough to tell... There should be a little gap between the carrier and the cones... If they touched at all and there are grooves, your cones need to be machined and shimmed, all depending on the condition of your carrier of course.

 

Yea I agree the pics arent great. I do have a gap on both cones. One side is flush with the housing. The other ones has a small gap. Should I use a feeler gauge to measure? If so what is a decent gap?

Thanks for your help

 

see if these pics work. The one side is good. BUt the other is down a little.

 

They look good to me. I rebuild a 9 bolt that the cones had hit the carrier... It worked good for a few thousand miles, then the posi started going out again... Always locked up good at the track though

I would think yours is fine, just try not to do burnouts in the rain and you should be good to go!

It wouldn't hurt to get measurements with a feeler gauge though... I might even machine a bit off to prolong it from hitting the carrier.

 

Looks like you're about 1/2 way to the end. Enjoy.

 

Ummm, just a little tip here. If you're trying to refer to the POSI cones being okay or not, you posted pics of the carrier bearings! These have nothing to do with the posi cones.

 

actually there's a small sight window where you can see if the cone has bottomed out or not so it is visible in those pics, they're just a little poor quality and it's difficult to estimate from pics in general.

 

Oh I see now. I figured there was probably something I was missing. Lol. I've messed with 9 bolts a little bit, but not really enough to know about that little sight window.

 

Ive heard this before... what is it about rain burnouts that's so hard on them? I figured less traction against the posi would stress it less???

 

Yeah it kinda goes against general logic that doing a burnout on a slippery, wet street would be worse on a posi huh? Lol. The posi unit seems to be one of the major "achilles heels" of the 9 bolts though. Seems like they go bad more often than even the stock Auburn units in the 10 bolts.

 

Go to any drag strip and watch the street cars when they do their burnouts. If they get in the water and do a long burnout many of them will spin both tires for a while, and then one will slow down and stop spinning. This shows up a lot in the 5.0 Mustangs with the Traction Lock and with F bodies with the Auburn. I don't have a good explaination for why this happens, but it is VERY hard on the differential. When one tire stops spinning the clutch or cones start slipping and this build up a lot of heat in the differential and the oil. It also causes rapid wear on the cones and galzing on the clutches.

 

So are you recommending a dry burnout? Or no burnouts? At some point at the track burnouts are just part of the deal.

I love my 9-bolt, I'd really hate to blow it up.

 

If you are building a drag racer that will get used on the street then use a Detroit Locker. If you are building a drag racer that will not be used on the street then use a spool. If you are building a street car that you will take to the drag strip from time to time with street tires then use a clutch type limited slip differential and stay out of the water. If you want to run drag radials and do water burnouts then be prepared to rebuild the differential from time to time. The rear end is no different from other parts of the car. If you run it hard it will require some maintanance to keep it working properly.

 

Well that explains it then. I didn't realize the clutch posis had that excess slippage problem when doing burnouts in the water box. Won't hurt a Zexel-Torsen, Truetrac, or Detroit Locker, but yeah, any clutch type unit, be it cones or flat plates, that makes sense that it'll burn it out quickly. I've got a Torsen carrier sitting on my workbench that I'm going to put in eventually. However, quite amazingly, my original Auburn unit is actually still functioning well at the present! I don't abuse it much, but I'm still surprised that it hasn't given up the ghost yet.

 

So what is a good procedure for a street/ strip cone posi rear?
No burnout? 3-5 second dry burn to clean the tires? Roll through the water or go around it?
Also I've read on here that 9 bolts wear faster with an auto than a manual, would a higher stall make a difference?

Personally, I will be running a 9 bolt with 3.70 gears that is fresh, and 275/60-15 Mickey Et streets. I'd hate to trash the diff!

 

Hey Sleeper. I don't really know any specific advice to give you on your 9 bolt posi unit, other than try to treat it as nice as you can! While the 9 bolt rears are somewhat stronger than the 7.5" 10 bolt rear, as you probably already know, the posi units have a pretty bad reputation for going south. I'm not sure if a water box burnout would necessarily hurt it, especially with a good, strong gear like the 3.70 ratio. Doing donuts or fishtailing burnouts would probably be a bad idea though. That puts a significant load on the cone clutches since one wheel will be spinning at a different speed from the other wheel. Anyways, good luck with your 9 bolt, and I hope it'll hold up for a while if you treat it good!

 

Thanks Pat, I'll take your advise. Hope it holds up for a good while. I have a back up I'll be building just in case.