Welcome to the next installment of the Topic of the Week (revisited) to run from 5/3/2002 to 5 /10/2002 The subject for the week is all about what is in our rear ends, no pun intended, well maybe a small one, . Some suggested points of discussion: - Why gears help - Carrier differances. - Limited Slips - Posis - Lockers - Spools - mini spools - #of splines for various years - Low buck options - pricing - What to use in which application

I now have two SLP take off pois units. Can I put both of them in my differential? All kidding aside I did buy another one for future plans and as long as their selling them for $85 plus shipping I thought I'd go ahead and get it. This is the last year that they will be selling them or should I say as long as they have orders for Firehawks and SS's they'll sell them. SO GET YOUR ORDER IN NOW or asap they won't last forever.

Just thought I'd let everone know.

Steve

well i have 3.73s richmonds in my rear end with a slp takeoff posi.
the car is pretty much stock and the difference is huge. no times yet, but just the fact that the back end goes out when i spin is well worth it. traction is not a problem with the 255/50-16s kumhos. from a dead stop on a good surface if i floor it the tires will barely spin. the transmission shifts harder due to the gear change as i can get second gear rubber when on a smooth surface. i love it and the mod will just help me more and more with future mods. plus now i can leave respectable marks

People always say that the RS's never came with posi stock but a buddy of mine has posi on his 91 RS 5 speed.

I have a 90RS with 3.08 thats posi. Least itll leave two black marks and (now that Ive found out) and when jacked in the rear bth tires spin in the same direction. But when you let one side down, with a lotta force you can turn one independently but someone said that is just so the car can corner. Is my car a freak or just a rarity? Im the second owner and all I know is the guy ordered it how he wanted it. Always wondered why h go p. locks and no p. window??

My pondering thoughts are to go from 2.73 open to 3.42 posi and get the speedo done as well. Is there going to be a problem with the carrier? Should I go 3.23's with posi for my 2.x carrier?
If I decide to keep the 2.73's and not change the gears (I have plenty of HP, and think I'll be just fine.. I'm not in it for the 1/4 mile essentially...) yet get the posi and decide to change the gears later, will I need a new posi? I am going to do this after my header install....
Another question: is limited slip more expensive? I don't want both my rear wheels spinning at the same speed when I am cornering. I thought the posi's were limited slip already? I don't want rear-end hop, or tearing the tires up when I am cornering.

I have so many questions about this!

"posi"==Positraction®==limited slip

RSs could be ordered with posi. I think it was usually with the F41 suspension and 16 inch wheels (and you possible had to have the 5-speed). The history buffs would know for sure.

see thats the thing. I have the FE1 susp. and 15 inch wheels. I do have the T5. ill try to get under it tommorow and get the diff #'s

ok...couldnt wait till tomorow.....the #'s I got off the diff are: 22522676. If anyone comes across something in the #'s let me know what you find. Thanks!! Also GM N was on it.

I have the F41 suspension, A4 though. No posi. Musta had to get the T5.

Ok, here's my question dealing with speedo gears.

Since I have the electronic signal, what do I need to buy? Auctually, at home I have both the two gear set that I thought I needed in the beginning, then someone told me differently and sent me a speedo gear outa a stock 3.42 car that has a gear attached to a black housing. Same thing that is under my tranny, but Im assuming it has a different gear. Which one will I end up using?

I'm running 3.73's in a buick grand national posi unit.

Chuck, you can find the gears needed on some of the websites, for 3.42 I'm not sure, I had to get two different color gears. Once you pull that black piece out of the tranny there is another gear that you pull off inside the tailhousing that needs to be changed along with the conical shaped gear on the fitting. As far as I know they don't make it so that you can just unplug the conical gear and get one that'll adjust for the change.

you shouldn't have too many problems running the 3.42's in a 2.x carrier, I'm running the 3.73 in it and haven't busted anything yet, although I have heard of people who have...

Mike

Ok, cool. I got the gears at home (forgot the how many teeth are on each... too much unless calc info in the brain ), but I was just curious as to whats up.

Thanks!

I've got an '88 sports coupe. It's had 26 spline axles, open differential and 2.73 gears from the factory. I left the axles, but, I've replaced the gears with 3.73s and the differential with an Auburn posi unit. The change was incredible, I would reccommend this for anybody. Beware, however, after the change I got some terrible wheel hop off the line when launching hard. New lower control arms fixed the problem.

Hey burntblues, are you sure about the grandnational posi? They came with an 8.5 inch differential not the regular 7.5 inch like in all the other g-bodies. If you are running it how did you get it to fit? That would be a good swap.

As far as I know the unit came from a grand national. I took the whole rear axle assembly, but unfortunatly it was already pulled from the vehicle. It was my first time ever pulling and replacing one, but the unit just dropped right in for me. It could have also been from a regal t-type maybe?

Like I said though, I think they told me that it was from a GN. Interestingly though even with the change in carrier and gears it wasn't necessary to change any of the shims. Axle splines were different though but they still worked with my axles...

-=-Mike

My 92 RS came with limited slip 2.73s stock so not all TBIs don't have limited slip. Maybe I just got lucky but the 2.73s suck, gonna be 3.73s sooner or later.

Andrew

I have the SAME numbers on mine and i belive it is 3.42 posi and mine came with a 305 auto unsure if the rear is original though

My 91 Firebird came with an open differential and 2:73's. I first swapped in a set of Richmond 3:73's but still with an open differential. Wow what a difference the gears just made. Then I went with an SLP Take-off unit on sale over at SLP and a set of 3:42 GM Motive Gears and it made an awesome difference. Deffinetly recommend this setup to anyone that wants a great mod u can feel.

I too did the SLP take-off posi last year with 3.42 gears. Best mod yet. Much stronger running car and still gets 26mpg on the highway with cruise set at 72-75. I feel the 3.42 is a GREAT street gear and runs good with the TBI system. The 28 spline axles are also a worthy upgrade if your car didn't come with them since the axles are a larger diameter and thus stronger than 26 spline. If your going to mod "try" and do-it-right-the-first-time. I hate redoing a mod because I skimped a little because of short funding.

My buddy is looking to upgrade his 26 spline to a 28 spline but I am not sure where he would go to get the parts and upgrade it. Does anyone else know?

got a couple of questions... what is the easiest way to check if my car has a 26 or 28 spline axle??? cause i kinda wanted to order the slp posi but it won;t work with the 26 right??? aww ok i have a 2:73 rear but if i stop and do a burn out it spins both tires but i jacked it up and when i spin one wheel the other spins the other way... if i don't have posi whats going on with the 2 tire burn and no posi?? thats about it for now ..

Thats correct. I think they started making 28 splines in 89-92 but in 89 some cars had it and some didn't. Probably have to check ur VIN or RPO codes to see if u do or not.

Where do you get a take-off SLP posi? How much does a shop charge to set up a rear with new gears and posi from a 2.73 open?

Thanks

http://www.slponline.com/view_produc...TNUMBER=64501T
Here is ur SLP Zexel-Torsen (Take-off) posi. You have to make
sure u get carrier 3 gears when u have this posi installed with them. And shops charge u for labor and replacing ur bearings and shims. Cause they will have to do that in order to install it. Usually costs from anywhere between 250-500 I got mine done for 240.00 at this one place. You can get gears cheap at this website.
http://www.gearsareus.com
They have GM Motive and Strange gears. There both real good.

i have a 91 bird l03 and plan on an open 3.42 swap to slp posi

can i use my axles from the rear currently in the car

assuming they r in decent shape...? :lala:

I know according to my rpo codes that I have a 3.08 rear but if your know for sure that yours is 3.42 let me know.

Yes by 91 all F-bodies and S10's had the 28 spline axles. Cheapest way to get 28 spline axles that I have found is www.car-part.com search and you can get them for around $100. If you have a U-pull it yard around then I am sure you can get them cheaper than that. As far as installation, I asked around and got a mechanic to come by the house and set the pinion depth and backlash for $50. I did all the work pulling everything out and he just set the gears and then I put it all back together again. 12k miles so far and one set of tires

LOL

should i just get a 4th gen rear with 3.42 gears or should i get the SLP carrier and new gears? id have to have a different rear to anyways right? could i always switch the gears in the 4th gen rear if i wanted?

"and we have no limited slips stock"

Mine does Still works great even after 129,500 miles. But my 2.73s gotta go!

ya I found an article to confirm that it was an option.

If u have stock 2.73s u would need 3 series carrier right so im looking in summit magazine at richmond gears they would be the *3.08 and lower carrier right?

Are all the SLP take-off posi's the same? I ordered mine and the guy on the line (Don) asked me what kind of gears I had in my car now and I told him 2.73s, but I forgot to tell him I was changing over to 3.73s. Should this cause a problem or am I ok?

mine has posi too stock

I have an 88 sport coupe with an auto. trans. and 2.73's in the rear...I am not sure if it's a 10 bolt 7.5" or 10 bolt7.625"....or are they the same? I want to know because the powertrax no-slip locker list both and that is what I am looing into getting.

IM looking at using a rear from a 6cyl 4th gen

#1is there anything i need to do to adapt this to my car

#2r the flanges on the brake lines the same?

#3can i use my old e brake cables?

it is a disk rear im looking at... yes its 6cyl with disc brakes(5sp at that)they started this in 97?

#4 is thier any difference in width of axel between the disc and drum rear end(4th gen)???

pretty sure that they are the same but i am not 100% sure

Ok gentleman, i tried asking this in an earlier post but i got no responses. Im going to swap 3.73's, posi, and a 5-speed into my 91 RS. its now an 2.73, auto, no posi setup. What #$%# gear do i need for my speedometer to get it working correctly? Does it being an electric speedometer matter? BTW, about how many rpm's would this swap leave me at around 70 mph.

Berlinetta, I don't think that it matters if the speedo is electric or cable driven when it comes to the gears. As far as I know the difference is that instead of having to pull out a cable you've got to unplug the connector from the sensor. After that you pull out the unit that is held in with a half circle piece of metal which I think is held in with a metric 10. When you pull that off then you have to remove the tailhousing which is held on with 4 15m bolts. Don't forget to remove the Torque arm and the exhaust hanger also. When you do that there is another gear that needs to be removed by pushing down on a clip and then sliding the gear off.

Put on the new gears (part numbers: 25513052; 8642620 for 3.73's) and reassemble.

Here's a link to the SE thirdgen site that shows how to do it... http://www.sethirdgen.org/vss.htm

Of course, all of this is for the auto, I don't know about the manual...

edit -- just found it, here's for the T5 http://www.sethirdgen.org/t5speedo.htm --

The worse part about the whole deal is getting the T/A back on.

Later man,
Mike

This thread hasn't helped me out at all, unfortunately. It has left me with more questions than answers.
I have the 2.73 open carrier on my car. 10 bolt.
I DO want to get the GM Motive 3.42's and posi unit for my car. The question I have is about the speedo setup on my 91 bird.
Can this all be done in one shot? Or is it replace the gears, then go to another shop to have the speedo gears done? Do they have to go inside the transmission to replace the gear too? How much will this end up costing to have it done correctly?
I am confused.

you should be able to have the same shop do it.

Doing the speedo gears yourself is pretty easy if you have an auto, with a manual it looks a little more difficult. Check out the links that I gave above to see whats involved. I did everything myself including the rearend gear and posi swap, so my cost only involved parts. If you've never swapped a rear end before then I would say to either take it to a shop or have someone experienced help you.

If you do a search though you can find prices for gear swaps...

-=-Mike

How does the Powertrax Locker compare to a posi?

Isn't that the one that you can change the pins in? Or can they all do that? I was reading up on that one, and it seems to be a very spohisticated posi unit. I was thinking about getting that one too, but was wondering if it is worth the difference!

no no no. replacing the speedo gears is easy. if the posi unit you want is the SLP on then get that one, some gm motive 3.42s make sure they are 3 series carrier. i got the speedo gears from SPL when i got the posi from them. for an electric speedo with 3.42s the part number is not on the website but they have a bunch of stuff that isnt on the website call them to find out. read the tech article it explains it perfectly

Will a 3 series carrier fit in my 2.73 rear end?
If I get 3-series motive gears, what all needs to be done?
I read the thing on the speedo gears. Seems like it will work out, but I am still a tad mixed up.

I just put one in my car. I left the gearing alone for now. I'm in a trade union near Chicago so it's not unlikely that in 6 months I may have a job that puts 120 miles a day on my car.

Anyway, the PowerTrax is what I would say to be "serious sh!t" I never took into consideration that it's not a 'limited slip' rear end. It's kinda like a Detroit locker, without the air. The teeth are always locked, except when going through a turn. The difference in torque being applied to each wheel throught a turn is what unlocks the posi. But give it a little too much throttle and the inside tire chirps. It does this because it's trying to spin as fast as the outside wheel.

I've only had it in about 2 days now and I am slowly learning how to throttle out of turns to help avoid that. I'm sure I'll get the hang of it.

And I have tested it out. It takes a lot to get the tires to spin at all now with the 2.73, but I did get it to. It was weird riding out a 150' fishtail in my LO3, auto trans RS

AJ

Cool! That sounds like fun! I want to get one soon, but I'll probably change the gear ratio as well.

Everybody is talking about 3.4X's gears.....what about 3.27's??? I'm looking for a good pick me up, but I'm very concerned about daily drivablity.

I was thinking something like this:

SLP posi
3.27 gears

Now someone mentioned something about getting "carrier 3 gears," what are they and what do they do??

P.S.-How's the quality of the SLP unit?? Or should I just anty up the money for an Auburn or Strange unit??

Oh yeah,....and what exactly does the SLP Zexel-Torsen Diff do?? And why is it sooooo much cheaper than the heavy duty one?? Is it actually a posi/limited slip unit, or just a better built original type diff????

No such thing as a 2.73 rear end.
You have a 10-Bolt 7.5 inch rear end with 2.73 gears.

You need a 3 series posi carrier to use 3 series posi gears (3.42, 3.73 etc) so yes it does fit.

The rear end needs to be removed, dissassembled and rebuilt with the new ring gear, pinion, bearings, carrier and 28 spline axles.

When it's done and you start making some real power with the motor you WILL blow this rearend apart... for a stock motor the 10 bolt is OK... Otherwise it is junk and will live a short life in a car that is raced. I already ruined one ring gear.

For a little more money you can get a 12 Bolt from Strange Engineering, or even better a 9" From Currie. Both are great upgrades from the OEM POS and will live long healthy lives...