I have heard from both sides whether to use Friction Modifier in the 9 bolt posi rears or not to because they are Cone Designed and the modifier actually wears out the cones.

What do you 9 Bolt users use for gear oil? And do you add or not add friction modifier?? Any problems..?

I have a 9 Bolt Posi 3.08 Drum. Do I have a 2 or 3 Series Carrier?

I want to put in a Posi 3.45 Disc, but I think I would need a whole new rear-end right? Or will a 3.08 ring and pinion swap out the same for a 3.45 ring and pinion or is there more too it?? I'm sure I could modify the drum to disc brakes if the gears swap out evenly. Let me know your thoughts..

 

IIRC you'll need to replace the whole carrier to go from 3.08 to 3.45 ratio. Also, I've had the same Amsoil synthetic gear oil with no additives of any kind in my 9-bolt since I put it in the car. Still working great after 8 years.

 

Your carrier is a 3 series carrier and is right for a 3.45 gear swap. Here are some links;http://9bolt.com/gearsets.html ,http://mpikas.blogspot.com/search?q=9+bolt+borg+warner, You should use a friction modifier for a 9 bolt. Any brand gear oil is fine.

 

Again.. I have one guy saying not to use friction modifier additive and another to use it. Anyone else have any input weather use the additive or not??

 

Just depends on who you talk to. Some people say use it and others say don't it will work fine. GM and most shops will say to use a bottle of limited slip.

This thread is full of tons of great info on 9 bolts:
https://www.thirdgen.org/forums/faq-...now-about.html

 

It won't hurt anything.

However, it also won't help anything, either.

It's not about "cone" vs whatever else. It's about, some carriers use clutches with organic lining like brakes or auto trans clutches, and THOSE are affected by the additive. Other carriers, like the 9-bolt, use metal clutches (one piece of which happens to be somewhat cone-shaped), and those are COMPLETELY UNAFFECTED by it.

 

I'm glad you said that, because that is just what I was thinking, but was not totally sure so did not post..
I know the limited slip unit in my Jeep rear end uses clutches and needs the additive, but was pretty sure the mechanical BW 9 bolt in my TA did not. I knew the guys that bought Jeeps with open differentials and add mechanical limited slips like the Aussie, or Detroit Tru-trac did not need additive.

 

You can all do what you want, as everbody has an opinion. But the tag on my '87 9 bolt original rear say's to add the modifier along with the original G-M factory repair manual. They must have a reason other than the few dollars it cost. What could a little more slippery grease hurt? But then you could use the extra $5 for two beers.

 

After doing a little research, both Amsoil and Mobil say about the same thing. LSD friction modifiers are to eliminate clutch chatter.. the exact quote from Mobil "(the friction modifiers in the lubricant enable the smooth engagement and disengagement of the clutches as needed)"

So if your LSD has no clutches the friction modifiers are doing nothing.

Want to know why the GM manual says to use it, because the people that wrote the manual were not the engineers, and even if they talked to the engineers - GM engineers did not design the BW 9 bolt unit. They just bought it from Australia slapped in the 3rd gens (and only for three years at that) and probably didn't care how it worked, and weren't going to change the manual from how it was previous years if they didn't have to.

 

Clutch or cones, there's friction. You obviously know more than the G-M publisher's, and engineer's, and have been around alot of 9 bolts, so we'll take your word for it.

 

Don't use it. The posi additive is a bandaid fix for hammering wet plate cluthes like in the 10 bolts, eatons auburns...... You do not want the cone to slip even more than it does from the factory plus years of wear added. If it doesn't hammer you will not need it.

 

What he said ^. I have the 9 bolt and have been running it for 2 years without friction modifier. The only reason to use it is if you have clutch chatter going around corners. Since 9 bolts are cone style posi's you dont need the additive.

 

A guy I know had a perfectly fine 9 bolt, he then changed the oil and added the additive because he was told so by a "reputable" shop. Didn't even take a 1000 miles and some slalom courses to get it to slip completely. He caught it immediately because of his performance on his last slalom outing, I rebuilt the thing for him. The cones had jsut started kissing the housing. it was full of very fine metal particles from the clutches always slipping.

Here's a pictorial of that axle, just pics...no blablabla

 

 

 

 

 

Twin_Turbo; First, you could be truthful and tell how many miles were on that rear before the 1000mi oil change. Looks like 135000+ miles to me. If you think them cones wore down to touch the carrier in 1000 miles with a modifier in it, then the modifier must have been made of steel shavings. People on here are looking for info. You did a fine job on the rebuild, I'm sure you could give better advice than don't use it or it will ruin the rear. There are many rear end rebuilder's out there with plenty of experience with both the 9 bolt and the 10 bolt, Dana etc. that may disagree with you. I'm sure doing slalom course's helped wear out his rear quicker than normal? Anyway,You still did a nice job on the rebuild.

 

I'm not sure, I think there were 80K miles on it. The guy does a lot of slalom driving, it was fine all the time. Sure it wasn't brand new, the cones had worn but he went from a perfectly fine working posi to a completely dead one withing a very short time after changing the fluid. Most of the shavings in the fluid therefore are therefore from that latest interval (apart from those inside the case, they easily accumulate there and won't flush out with an oil change). uif it wore just as normal the posi would go out slowly and not almost all of a sudden. On my 87 camaro the posi became progressivly worse. On my 88s it's working flawless, there is no additive in either of them.

The posi additive is a bandaid, it's originally not even intended however it was added because of complaints of clutch chatter in auburn and eaton posis. If it doesn't chatter/hammer without it you should not add it. it increases slip and thus wear.
For instance, on C2 & C3 Corvette Eaton 10 bolts a lot of people remove the preload springs & plates and tune the posi by shimming the clutch pack, this does increase the posibility of clutch chatter and therefore 2 bottles of additive is used. That's how effective that stuff is.

But, let's agree to disagree and let the guy run without additive. If it pops and hammers he can always add some.

 

The shop manual and the tag on the rear end all recommend GM's posi additive. I don't know how much more information is needed beyond that to answer the question. I've run the additive in my 9 bolt with no problems. Not allowing the cones or clutches to slip as the car is turning would seem to me to put more stress and wear on the components. GM wouldn't spend a 1/100th of a penny on a part if it wasn't absolutely needed.

 

BS!!!! GM gave Ross Perot 900 million dollars for less than 300 million dollars worth of stock just to shut him up and you want me to believe GM pays any attention to pennies of stupidity in their manuals. But I will research this further, definitive answer forth coming.

 

Just a follow up to the comments about BS - I worked with GM plants and engineers for 16 years all over the Midwest and whatever may have happened in the Board Room (incredibly stupid) in no way impacted what was going on in engineering. The GM engineers were the best in the industry for a long time, when the management let them be anyway. We were constantly competing over pennies on the projects I was involved in. It's simple math - if GM could save $1 per car by not using additive the savings would be in the $ millions - just common sense.

 

The 9 bolt rear end was not built by GM,, but by Borg Warner in Australia, so the GM engineers would not have had anything to do with that portion of the manual. And if the GM 10 bolt did use the additive they may have assumed the 9 bolt was the same.
2. Just because the manual tells the consumer to buy and use the additive, does not mean they put it in to start with. Especially it it came pre-assembled from Borg Warner. Taking the info out of the manual or adding separate information would have cost them money, not saved them money.

 

I was born in Michigan, grew up around the auto industry and lived and worked in Detroit until a few years ago. If as a whole they were they had any common sense, their market share of 50% of all vehicles sold in the US in 76 to 40% in 1985 to less than 20% now would not have happened.
Also he 9 bolt rear end was not built by GM,, but by Borg Warner in Australia, so the GM engineers would not have had anything to do with that portion of the manual. And if the GM 10 bolt did use the additive they may have assumed the 9 bolt was the same.
Just because the manual tells the consumer to buy and use the additive, does not mean they put it in to start with. Especially it it came pre-assembled from Borg Warner.

 

You people act as if $5 of additive is the worst thing in the word. Whether you think the G-M engineers had anything to do with the 9 bolt or not, I'm sure G-M new enough about that rear to put it in the f-body. And yes additives are recommended for posi rears. If you don't want to use it don't. But don't try to use you B-S to tell someone they should'nt. I grew up in Wi., which has nothing to do with f-body cars. So unless you were a "G-M" engineer, do some research on posi additives.

 

HiG4s - I don't know what to say to these new comments - what is your agenda? So did you work for the Big 3 or any of the Tier One suppliers or just in Detroit? Many of GM's drive train parts were sourced from other suppliers (all are now) so what is your point? GM worked closely with the supplier engineers on all sourced products to insure that warranty costs were reduced (I worked for a Tier One supplier). Since they also care about what they pay for the components they wouldn't want to pay for an additive that they didn't need but they would want to pay for it if it reduced warranty costs. I would be very interested in seeing any documentation that BW left the additive out when they spent the money to produce metal tags specifying that it be used.

The information in the shop manual is specific to the Borg Warner 9 bolt so you are correct that it cost them to add it for whatever that is worth.

You still haven't explained why you think the additive is harmful. I'm not going to waste anymore time on this issue -it sounds like you just want to argue.

 

I actually worked for an auto co-operative company for 12 years, that had offices in all three of the big three's HQs. I also have a friend that was a design engineer for GM.

My only agenda is to make sure that OPINION is not taken as FACT!!!!

Speculating on how smart and/or cheap engineers at GM are to justify using gear additives is ludicrous. We can all site a plethora of inconsistencies in a multitude of manufacturers manuals, but if someone wants to believe the original manual is correct that is fine, but when I find reputable, verifiable sources (Amsoil and Mobil) that contradict the manual I have to question it. Now I am not that up on Third Gen 9 bolt rear ends, but I have been around 4x4s and non-BW mechanical limited slip differentials for awhile and they don't need additives.

Still maybe the 9 bolt does, if it does I'd like to know as I have one, but I don't want opinion, I want facts.
One other fact I do know, is I had to have work done on my 9 bolt, it took me weeks to find a shop that knew how, and they did not put any additive in mine.

 

Bottom line is, the additive is there to stop clutch chatter in wet plate clutch posis.

Run the 9 bolt without it, if it doesn't chatter/hammer you will not need it

 

my if people would hear me read carefully reading the above the $5 stuff is mostly for somebody who is picky on a little noise NOW if a car NEEDS modifers it wont ever really be knew other wise battle it out a mod should probably lock this