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Rear End Gears

 
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Leejo2005
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Joined: 12 Jul 2009
Posts: 466
Location: Kennewick


PostPosted: Wed Dec 30, 2009 8:52 am    Post subject: Rear End Gears Reply with quote

I found this axle assembly on craigslist and I'm probably going to pick it up after I get off work tomorrow. I do, however need to change the gear ratio and I'm planning to go with a 3.73 gear. The assembly is a posi unit from a 1989 IROC with 2.77 gears. I'm posting the links below to the craigslist post and to the gear set I have picked out.

I need some expert knowledge, or at least one of your guys' help in this area to verify for me that this gear set will work in this setup.

http://www.summitracing.com/parts/SUM-741012/

http://seattle.craigslist.org/sno/pts/1526089511.html




If I agreed with you we'd both be wrong.
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Al Hasse
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Joined: 19 Nov 2005
Posts: 4379
Location: Bremerton, WA

1992 Chevrolet Camaro RS

PostPosted: Wed Dec 30, 2009 9:00 am    Post subject: Reply with quote

That's a 9 bolt rear and I don't think that 3.73 gear will go in it.

I've heard this place is one of the very few to get parts for that rear end, and your equivalent gear would be 3.70.

http://9bolt.com/

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redlava
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Joined: 02 Feb 2007
Posts: 448
Location: Bremerton

1986 Chevrolet Camaro Z/28

PostPosted: Wed Dec 30, 2009 10:06 am    Post subject: Reply with quote

The first problem is that is a two series carrier in the rear you are looking at, which will not allow you to put a higher gear ratio set into the rear. The second problem is the rear end you are looking at is a 9 bolt rear, where as the gears you picked out for the 10 bolt rear.
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Al Hasse
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Joined: 19 Nov 2005
Posts: 4379
Location: Bremerton, WA

1992 Chevrolet Camaro RS

PostPosted: Wed Dec 30, 2009 1:08 pm    Post subject: Reply with quote

That's the right gear for a 2-series carrier as Summit says it fits 3.08 and numerically lower carriers. Unfortunately, it won't go in the 9-bolt rear.
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aaron_sK
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Joined: 23 Jan 2006
Posts: 8834
Location: Back in beautiful Tacompton

1987 Chevrolet Camaro IROC-Z

PostPosted: Wed Dec 30, 2009 5:53 pm    Post subject: Reply with quote

9bolt.com is on the other side of the planet. Their shipping charges were exactly 100% of the cost of the item when I was shopping for gears for my IROC ($220 for 4.11's + $220 for shipping).
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Schultzy89GTA
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Joined: 08 Jan 2004
Posts: 4417
Location: Gresham, OR

1989 Pontiac GTA

PostPosted: Wed Dec 30, 2009 7:48 pm    Post subject: Reply with quote

There are a few other places you can get 9 bolt gears from. The selection is pretty limited though. Usually just the 3.70 gears. If you need me to dig up the links let me know (on my other computer).

-Schultzy

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Leejo2005
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Joined: 12 Jul 2009
Posts: 466
Location: Kennewick


PostPosted: Wed Dec 30, 2009 8:59 pm    Post subject: Reply with quote

I'm not too set on an exact gear ratio... I recently swapped my 700r4 for a T5 and with my current I think 2.73 gears the car is hard to keep from stalling when starting from a stop. In 5th gear, for example, for the engine to be turning 4500 RPM the car would have to move 187 MPH, which I don't see happening anytime soon.
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Leejo2005
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Joined: 12 Jul 2009
Posts: 466
Location: Kennewick


PostPosted: Wed Dec 30, 2009 9:03 pm    Post subject: Reply with quote

I was just looking on Craigslist for my area and found a guy selling 3 10-bolt posi rear ends for $250 each, maybe he has one I can make use of. I'm tired of my bad gear ratio/one wheel wonder.
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alloy
T56 Elitist


Joined: 25 Jan 2004
Posts: 1716
Location: Vancouver, WA

1987 Chevrolet Camaro IROC-Z

PostPosted: Thu Dec 31, 2009 2:54 pm    Post subject: Reply with quote

You have to realize if it's a stock 10 bolt posi out of a 3rd gen the posi is shot. I'd say there is a 99.99999999999999999999% chance it will one wheel peel on you. It will act like a posi when you turn it by hand, but that's about all it will do. They wore out very quickly. Mine stopped working as a posi with less than 5000 miles on the car. The newer 4th gen rears come with a Zexel and that works ok, just not too ok for autocrossing. When I was in a hard corner with race tires on I'd spin the inside wheel badly. But in a straight line it works pretty good for me.

Just be aware that the older units are worn out. I'd don't want you to be disappointed if you spend the $$$ and go to all that work and it does the same thing you have now.

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Al Hasse
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Joined: 19 Nov 2005
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Location: Bremerton, WA

1992 Chevrolet Camaro RS

PostPosted: Thu Dec 31, 2009 3:25 pm    Post subject: Reply with quote

I suppose then I was one of the lucky ones and got a working posi from a 1982 TA (flea now has those gears). I bought the rear mainly for the disc brakes it had though, but I've changed those out too. I've also changed out the posi for a new Eaton unit.
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Leejo2005
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Joined: 12 Jul 2009
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Location: Kennewick


PostPosted: Fri Jan 01, 2010 2:42 pm    Post subject: Reply with quote

Right now I can hardly make it through an intersection without spinning a tire, even with my old tired 305. I've decided to wait for the moment on getting a new rear and focus on getting the new motor built. Anyways, if I'm trying get my bird to grab a bit better what rear would you recommend? (I am not dropping $2,500 on a brand new unit)
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Al Hasse
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Joined: 19 Nov 2005
Posts: 4379
Location: Bremerton, WA

1992 Chevrolet Camaro RS

PostPosted: Fri Jan 01, 2010 3:16 pm    Post subject: Reply with quote

I like the ratio we ended up putting in my 89. I took most of the advice of the crew and bought new parts. My axle housing came from a 1982 TA, and it's the only part of the rear end that hasn't been changed since. I acquired a 10 year old 3.73 ring & pinion (never opened or installed) from another crew member. Then I got a new Eaton posi carrier and a new set of axle shafts. I spent a total of about $750 for all.

I like the 3.73 ratio with my T-5, I'm off just a little with the speedometer gear, but at 70mph, the motor turns about 2300 in 5th gear. Wet pavement can be quite fun if trying to use first gear, even worse in snow Shocked

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Leejo2005
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Joined: 12 Jul 2009
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Location: Kennewick


PostPosted: Fri Jan 01, 2010 3:34 pm    Post subject: Reply with quote

So basically I should try and find an axle assembly/tube, put a new carrier in it and gear it to my liking?
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Al Hasse
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Joined: 19 Nov 2005
Posts: 4379
Location: Bremerton, WA

1992 Chevrolet Camaro RS

PostPosted: Fri Jan 01, 2010 3:43 pm    Post subject: Reply with quote

Or use the tube you have. I picked up the one I have for the disc brakes it had - only to change them later Laughing Cool
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alloy
T56 Elitist


Joined: 25 Jan 2004
Posts: 1716
Location: Vancouver, WA

1987 Chevrolet Camaro IROC-Z

PostPosted: Fri Jan 01, 2010 3:56 pm    Post subject: Reply with quote

You know 3.42 rears are cheap and fairly easy to find in the bone yards. If you look some times you even run across a 3.73 rear now and then.

Like and idiot I ran across a 3.70 9 bolt that had the axles gone out of it and I didn't get it, and one our our crewbies went and pulled the gears out of it. I don't remember who pulled the gears, but now I'm kicking myself big time for not getting that rear for my car. The 3.70 is just about perfect with my T56 I have now. At the time I still had the weak little T5 in my car, and 3.70's would have been too much gear for me back then.

Live and learn I guess.

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Al Hasse
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Joined: 19 Nov 2005
Posts: 4379
Location: Bremerton, WA

1992 Chevrolet Camaro RS

PostPosted: Fri Jan 01, 2010 4:13 pm    Post subject: Reply with quote

I came across a set of 3.42 gears, with posi IIRC here in the Bremerton yard. They were in a 96 or 97 bird. I wanted to pull them from the rear end, but was against yard policy Crying or Very sad They wouldn't let the gears go without the axle housing.

The car might still be there,I didn't notice last time I was there. I took the e-brake tunnel bracket and front cable from it a while back, I also have the PBR backing plates from it.
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Leejo2005
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Joined: 12 Jul 2009
Posts: 466
Location: Kennewick


PostPosted: Sun Jan 03, 2010 2:48 pm    Post subject: Reply with quote

So it seems I have been asking the wrong questions here. Depending on what axle tube assy is installed in my car can I put a posi carrier in my non posi rear? If I wasn't stuck on a ship for the next day or so I'd go look at my RPO codes and see what I have currently.

I went to the yard in Poulsbo yesterday, I didn't find any rears that looked worth using, but found an '88 IROC that I bought the front bumper covers and gfx from, and its hard fuel lines and filter for my TPI swap, got it all for $50 + tax. Hopefully when I get off work tomorrow the rear bumper will still be on it so I can snag it too.
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Al Hasse
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Joined: 19 Nov 2005
Posts: 4379
Location: Bremerton, WA

1992 Chevrolet Camaro RS

PostPosted: Sun Jan 03, 2010 9:56 pm    Post subject: Reply with quote

Leejo2005 wrote:
So it seems I have been asking the wrong questions here. Depending on what axle tube assy is installed in my car can I put a posi carrier in my non posi rear? If I wasn't stuck on a ship for the next day or so I'd go look at my RPO codes and see what I have currently.


I could be wrong, but I don't think the housing matters at all. What matters is the thickness difference of the ring gear between 2-series and 3-series and the carrier and/or ring spacer to match. Since you want to change to a 3.73 gear and carrier, what you should need is a good 3-series posi carrier and the other 3.73 gear than the one you had linked. It would be a good idea to get new axle shafts too, with the spline count to match the carrier - preferably 28 spline.
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