I'ved been building my 88 IROC for the 1320 & Pro Touring. My new Borg-Warner just broke and I HAVE to make a repair choice this week.

I posted a thread under the drivetrain thread this weekend explaining the issue, but am not getting hard facts that will help me make a solid stress free repair decision.

I'll drop in the facts from the thread I started, but what I really need to know is if I should fix the Borg Warner unit or do some sort of upgrade. I'm running out of $$$$ funds quickly, as I just replaced my entire suspension, brake system, stage III 700R4, completely rebuilt 9-bolt, and am working on a totally new 355 engine.

You guys are the knowledge powerhouses. You will know what I can get away with short term and what I need to plan on for long term. Is there a short-cut I can take that won't cost me $2 thousand bucks this week??? I want my IROC to be ready to start running my local Sears Point Racetrack Wednesday Night Drags season that starts this coming March.

I drive over to Twin Falls Idaho every two months to visit the old family farm and love to drive hell bent for leather across the Nevada desert, yet I'm trying to incorporate a very consistant 1/4 mile package. What I've got is a TPI heavily ported 355 small block that should pump out approx 355-365hp at the crank along with somewhere near 400 ft lb of torque. I gutted my 2.77 9bolt and installed 3.27 gears with all new bearings, seals, etc. My torque converter is 2200rpm and I tend to soft launch.

This last year was my first season. I went 20 times to my local track with the wife's Infiniti G35 and ended up taking home 6 trophies. It got me really amped up and I started pounding out my IROC so she could have her car back.

So, should the 9-bolt have held up and this was just a freak thing? Will this rear end start to fail within this upcoming season? Could I replace it with a 4th generation rear end? or????

Please Help me; I have to give the shop my decision by the end of this week.
sincerely, Nitro-Nicky
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.....Here's my initial post...........



9-bolt posi had nervous breakdown; Why???

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I purchased a lightly used 3.27 carrier & gears to upgrade my 1988 IROC's 2.77 posi. I used what is considered one of the very best rear end shops in North Cali; (The Rear-End Shop). I had them evaluate the parts I purchased to be sure they were appropriate. The shop accnowledged their quality and light use and rebuilt my Borg Warner 9-bolt with all new bearings, seals, cap bolts, etc. Everything seemed fine. This was approximately 6-months ago. The only time's the car has been driven is back & forth a few times to a transmission shop, and a few other shops. My old L98 block has knocking rods and the new engine isn't ready yet, so I've only done a small handful of burnouts while testing new parts.

Last week I finally took the car out for a three hour freeway cruise and then stripped the undercarriage down for all new end to end suspension (Moog, UMI, Spohn). After bolting up the Torque Arm, I ran the car while it was on the lift and noticed the rear end was so sloppy that it was loudly banging when put into gear and when pressing down on the brake. When I turned one of the rear wheels by hand, the opposite wheen didn't turn. The rear yoke moved about 3 inches before engaging.

I took it back to the rear end shop yesterday and when they pulled the rear cover off , there was a load of shrapnel in the bottom gear lube. The posi was completely eaten up. Allegedly, the technician stated; the only way for this to have happened was for someone to have hammed on the rear, which caused the two rear wheels to spin at different speeds.

Since I'm the only one who drove the car, other than the tranny shop who's had to fix their initial 700R4 build a couple times so far; and that I have to baby the engine so it dosn't throw one of the loose rods- how could this have happened???

I spoke today with the owner of the shop, and he didn't make any excuses or try to blame me for driving it hard; but he did suggest that the 9-bolts are prone to posi cone failure and I might want to rethink what I'm doing. I'm going to be using the IROC for regular commuting and weekly runs at my local dragstrip. I'm only going to be running approx. 360hp/400tq max; plus with the automatic trans, there should be less of a shock hit off the christmas tree.

I thought the Borg Warner unit was way-way better than the usual Camaro rear end and would stand up to 600 hp off the line???? Did I do something wrong or can the shop be wrong or is there a better set up that won't cost me an arm and a leg??? I just dumped in $3 grand in the suspension and I still have to pay for half of my new engine and get it installed. Now I am Soooooooooo dang Frustrated!!!!!!!!!
Nitro

 

here was a follow up post......
Do I Ever Need HELP!! 9-bolt posi had nervous breakdown; Why???

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Quote:
Originally Posted by RebornFromAshes
What actually broke in the posi? Knowing what actually broke could help to figure out what could have been wrong with the posi before.

If I had to toss a guess I would say one of two things happened. Either the housing is bent and is putting stress on the posi or that the posi had some cracks that were not easy to spot.

When they did their inspection of the parts, did that include disassembling the posi and carefully checking each piece? My guess is a loud "NO". They probably just quickly looked at a few things to get a feel for how much wear the unit had.

If the unit had some kind of a crack then they could have done a fine job of rebuilding the axle and still had problems. For such a short life it is hard to see pinion preload or carrier bearing preload being a factor. Those would only be likely to cause gear damage in that time. The only way I could see for all top-quality parts to fail that quickly would be, as suggested, you simply put more torque through the axle than it was designed to handle.

The 9 bolt axle is a decent axle, and it is a bit stronger than the tiny 10-bolt axles used during the same years. A good condition axle with a modest gear ratio (3.45/3.27/3.08) should have no problems handling the power levels you are talking about. I would say the same of the 10-bolt, especially the later units with 28 spline axles and the slightly larger ring gear. This is around the power range that GM offered full warranties on during the last years of the F-Bodies' life. In other words, you should not have to buy an aftermarket axle to have a reliable axle behind your stated engine.

You won't ever catch me saying a 9-bolt can take a 600HP full throttle launch. They just don't have enough meat most anywhere in the axle to handle that kind of abuse with any kind of reliability.

Now THIS is more of the type of information I needed; and I really-really appreciate your well thought out reply.

The current engine is still the factory 350 with approx 150k miles. It's run like total crap ever since I got it. Last time I checked, the torque was 90 ft lb down from the factory numbers. I finally got the last issue with the TPI system sorted out two weeks ago (the system was stuck in closed loop), but I doubt I was anywhere near the torque needed to destroy the cones.

What I saw, when the tech showed me the parts after the disasemble, was a round heavy bearing shaped object. The face was ground up with heavy grooves.

Now when they pulled off my aluminum heavy duty cover to do the initial check, the fluid was way lower than than it was supposed to be. They assumed I had changed the fluid and only put the amount of rear end fluid that went with the factory steel cover; thus, the gears must have 'burn't up'.
When they actually did the disassemble, it became more obvious (so they said) that the fluid was unburnt and they wanted to wait till the owner arrived to figure it out.

The trans shop got the IROC right after the rear end was first done and they built a stage 3 700R4. I know they test drove it, as they told me it would burn rubber shifting hard into 2nd. As I drove it home, it was shifting sledgehammer hard into each gear. When I went out to the car two days later, it was stuck in first gear and wouldn't upshift.

When the tranny shop returned the car, it shifted into gear firmly, but no longer sledgehammer hard. Then the new 2200 stall converter started acting up by shifting into the next gear earlier and earlier. Now it starts shifting up just above idle.

My engine builder told me that he thought I was making a mistake by using a 9-bolt. The rear end shop owner is telling me that if I fix it, it will probably fail within one season of Wed Night drags. I certainly don't have an extra $2000 to invest in a Ford 9 inch setup.

Whatever the shop did or didn't do, they did provide me with a one year warrenty and will fix mine or assist me in coming up with a different solution.
Did the 4th Generation have any better, more durable differentials than the 3rd's???

 

The 4th gen uses the exact same axle, only wider...

If you can find a used dana 44, you'd be okay. There are some for third gens floating around out there. They were service replacements for your 9 bolt.

The next thing is to start looking for used aftermarket rear ends. I have seen the Moser 12 bolts and some 9 inch setups in wrecked cars the last few years.

If you go 7.5 ten bolt, I'd swap to 28 spline AFTERMARKET AXLESHAFTS (around 400 bucks) and a used 4th gen Zexel torsen posi unit. They're pretty tough. You'll have just under a thousand bucks in it by the time you rebuild it and put your brakes on it.

I'd start saving for an aftermarket housing, If I were you. Like the Moser or Strange 12 bolt or Dana 60.

That's just me.

 

This looks like a dana 44, you'd need him to send you better pictures...

http://cgi.ebay.com/ebaymotors/82-92...em170188041063

 

Don't know what to tell you. Sometimes you get decent parts, sometimes you don't. Sounds like the tranny shop beat the car up 'testing' the transmission and hurt some parts. Doesn't sound like the rearend shop knew what they were doing, but how do I know. It could have been your 'slightly' used gears. Used is used, no telling what shape they were in.

I can estimate that I have at least 50 1/8 mile and 25 1/4 mile passes on my 3.73 9-bolt in the 11 years that I have had my car. I have most of my time slips back to 1997 when I bought this car. 60 foots range from a best of 1.84 on street tires back when I had the original 3.27 gears to 1.58 on a 175 shot now, usually mid 1.6's to 1.7's on motor. Me and a bud set the gears up and I bought them from 9-bolt.com back in 2003. I have never rebuilt the posi, and it is showing it age now, only spinning one tire in the burnout box when it feel like it. I've used 26x11x16 et streets on it since 2003.

It's not the strongest rear, but with an auto tranny and your power level I would think it would last a season being beaten up for 5 passes each weekend. I've got 98,000 miles on the car and the rear-end bearings are original. I would have them set-up the gears again on the tight-side or find another shop.

It's alot easier to find a shop that can set-up a decent rear-end then finding a shop to build a good 700r4.