I'm looking to purchase some 3.73 gears. I went to jegs website and now I'm confused about what I'm supposed to buy. I have 2.73 gears right now. Do I need a Ring & Pinon Set? Is this different than just gears alone? Also, I'm not sure if I have 10/12 bolt or if its 7.5, 8.2, 8.5. I didn't know I had to know all this, I just want some 3.73 gears. Maybe I'm making this more difficult than it appears. Could yall gimme a hand as to what I need to buy? Whats involved to change to 3.73s? And where you reccomend to buy them. I'd like to save some money if I can but I want good quality too. Thanks for any help.

1992 Z28 a/t 305 (stock)

 

Forgive my ignorance....but what is all this stuff about carriers?..2-seriers, 3-series? Should I know this? I feel kinda dumb right now but I need some education. I just bought my first Z last month. Thanks again.

1992 Z28 a/t 305 (stock)

 

I wouldn't get 3.73 gears. Especilly on a stock TPI motor. This is because the will get you out of your powerband faster. They make you rev faster and in a sense make your gears shorter. TPI motors especially your stock auto 305 breath really good till about 4500 rpm then they just fall flat(I know I have one). When you have 3.73 gears all your driving is spend at high rpms and this motor is not effecient up high. Go with some 3.42 and you will get better gas mileage and your 1/4 mile times will probably be the same if not better. My 305 with 3.42 can beat a friend of mines car with 3.73 and they are the same car but his is a 90. You need to gut your airboxes and your MAF.

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TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph

"Speed kills, wanna live forever, drive a Ford."

 

Forget the MAF thing you don't have one you are a Speed Density car. Sorry!!!

------------------
TPI 305,
Gutted airboxes,
gutted MAF,
K&N filters,
Corvette Servo.
14.9@93mph

"Speed kills, wanna live forever, drive a Ford."

 

What was involved when you got your gears changed out? I'm still not sure what I need to do.

 

Well..if you have to ask whats involved....you can't do it. it's pretty intricate. What you'd have to do is get the gears, an install kit, and take it to a shop. The install kit is $100 I believe...and shops vary, call around.

I agree 3.73's are prolly over kill for you. 3.23-3.42's are what you want.

You can also try to find a used, complete rear. It'll be much cheaper.

 

Thanks for the advice about getting 3.42s. I'll keep that in mind. I was reading this forum and read about 2-series/3-series posi's. How do I know which one I have? It seems like this makes a difference when buying gears.

 

You should have a 2 series.
IF you have under 3.27 gears, you have a 2 series. 3.27 or higher is a 3 series.

 

I'm assuming I have a 10-Bolt since its seems to be more common. I guess I'll have to get under the car and count the bolts myself. How can I know if its a 7.5, 8.2, 8.5? Also, if I get 3.42s, I need to get the ones that fix for 3.08 ratio and numerically lower numbers? (I have 2.73s now). Is this right?
What if I want to upgrade to 3.73s in the future? Will I have to buy the 3.73s for the low number or high number?

 

I have some of the same questions, and i also wanted to know what involved with installing my headers but did them myself (my first completed mod) with a total of zero problems. I realize headers are a lot different than gears and gears require much more precision, but at least give us an idea. Ring and pinion, just gears, new carrier??

thanks

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1986 Trans Am
305 TPI
"If it's not one thing, it's another!"
http://www2.hanover.edu/hierlmeier

 

Yes you need the gears for the 2 series if your factory gears are 2.73 now and later if you swap gears again. BTW are either carrier 2 or 3 stronger than the other? I just had 3.73's installed by a shop and am very pleased with them. Car really launches now compared to the stockers. Why go with the 3.42's if you are skeptical about maybe putting 3.73's in later. Look at some of the faster cars and their mod list. Usually they put 3.42's in and then upgrade to 3.73's. Why go through it 2, there can't be too much difference between 3.42 and 3.73. Good luck

 

Thanks for clearing that up. Yes, I wanted to go with 3.73s but some have said that it wouldn't be good with my stock 305 TPI. Is this true? I wanna get my gears now, but now I'm not sure which one to get. Anyone have a 305 TPI w/3.73s, any problems? And is there really much difference between 3.42 and 3.73? Thanks.

 

One more thing...If my stock 305 is restricting me, then what mod(s) should I do?

 

With my old 2.73's it seemed like I could keep up with alot of guys in 1st gear. But when I hit 2nd my rpm's would drop so much that I would fall behind and could hang there but could never catch up. Now I bet when I hit 2nd I'll have a better chance because of the less loss of engine speed. I also have a 305 tpi and yes it is not a high revving engine but neither is the 350 stock for that matter. Earlier this summer I was at the Back to the 50's car show at the MN state fairgrounds and talked to the guys at the TPIS trailer and they recommended 3.73's for my car.

 

You've got a 2-series 7.65" rearend which is the 7.5" for all practical purposes. You have a 92 Z28 so you should already have a posi unit back there. I think that 3.42s are good for your purposes - but if you ever intend to mod the car you should take that into consideration because where 3.42s might be cool now, you might want 3.73s or even 4.10s in the future if you choose to make your car that extreme. 3.42s are a great gear in my opinion - a good low end acceleration but plenty of top end as well. I am putting 4.10s in my RS, but I have an LT1 that is being built to take 6500+ rpms so 4.10s will work great for me. Especially since I don't care worth a wit if I have to cruise at 80 while pulling down 3000rpm.

If you're looking to get more performance out of your car and that is what's motivating you to get gears you might consider some other alternatives.

Headers give you a good boost in power. In fact I would suggest a full aftermarket exhaust. 1 5/8" headers and y-pipe, 3" in/out cat, 3" exhaust all the way back to whatever muffler you prefer. When you figure the cost of gears plus install kit can run as high as 300 or 350 and then you have to find a shop to install it for anywhere from 200 - 300 then you're looking at a total investment of 500 to 650 dollars. You can get, for example, Edelbrock headers and y-pipe for 300, and then go to a local shop and get a 3" cat for ~50, and a Dynomax aluminum 3" pipe back to a Dynomax muffler for about 200 to 250 depending on the shop. That's priced as installed. You'll end up with more power, better looks to the exhaust, and a MUCH cooler sound to the car.

With TPI there are lots of other things to do. If you're looking for ways to hop up the car post something in the General Engine page and you'll get all the info you could want.



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1991 RS LT1
every imaginable bolt-on, and an all-forged 355 on the way with an ATI following in '01

2000 C5 Coupe
black/black 6-spd, optional polished rims, 'mostly' stock....

"So what DOES the back of a Mustang look like?"

 

I have a 305 TBI. I recently put 3.73's in mine and I am VERY pleased with it. I could not even begin to tell you the difference it made. A "seat of the pants" difference. I didn't even notice a difference (other than time slips) when I did the headers and exhaust. It does sound GREAT now though!!. Get the 3.73's for the 2 series carrier, get the instalation kit and go to a shop for instalation. You will love it.

Eric

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Teal 1991 Camaro R.S., T-Tops,
Leather, Re-worked 700r4 also w/kit,
MSD ignition, MSD 8.5 mm. superconductor wires,
MSD Coil, ADS superchip, Open element air cleaner,
K-n-N filter, Gutted cat, Flowmaster cat-back system,
Edelbrock TES headers, March 3piece billet underdrive pulleys
3.73 gears
http://www.geocities.com/gitarz2/camaro.html
I was shocked to see that companies sold a taillight
set for a rustang! Since when do they have taillights????

 

Thanks. As far as how extreme I wanna build my car...I'm looking for performance in the mid-to-high 12s. I don't plan to use NOS, just raw Horsepower. So I know I will wanna drop a 350 (maybe 400+) engine later on. And I wanna be able to drive every day and take trips every once in a while to Atlanta. So I think 3.73s seem to fit good. I'm gonna run on this 305 till I can save up for a new engine. But this 305 needs a lil more beef but I don't plan to do much serious mods to it. Now that I know what to get, can someone reccomend where to buy the gears? I've heard a lot about Richmond and Auburn. They seem to be the way to go. Are there others with the same quality or will just about any manufacturer be okay? Thanks again.