I just ordered the Zexel-Torsen diff. and a set of 3.73's from SLP!

Im finally going to ditch the factory 2.73 one-legger. Ive had this car for almost 4 years now and it's slowly getting the way I want it.
My daughter HAD cancer so, I didnt have the extra money to put into it like I wanted. But now it getting there.

But anyway to make this thread a tech question, What gains should I get or feel.....

Thanks...........this board is great, Ive been here for a long time just don't post much, but you guys have HELPED me with all my 3td gen needs...

 

Way to go!! You should feel much improved acceleration and some have even reported BETTER fuel economy. Good things come to those who wait.

 

I did pretty much the exact same thing. I assume that you have a 700r4 tranny like I do. I cant giving you any quarter mile times becuase I did alot of other things at the same time (like intake, ignition, headers, gears drives, carb, etc.) What I found was that I had my acceleration really improve. Rolling starts are a lot better too. My biggest problem was that when I switched from 2.73 too 3.73 that my speedo was way off. I haven't been able to switch my speedo gears yet but I did learn to start driving of the tach. If you want I have made out a spreadsheet to put in my car for reference to speeds in each gear with a given rpm, I can send that to you if you want me too. I found that If I wasn't driving to college all the time I would have put in 4.10s with out any hesistation, and looking back I kinda wish I did. Think about what you want your quarter mile trap speeds to be to make sure that the 4.10's arent to low.

 

I take it she made through the ordeal ? VERY GLAD to hear it !

Of course we all look forward to hearing about the 2.73 swap as well. It will make a world of diff to the car most people don't believe how much -- until they try it.

good luck,
RP.

 

Palric, she's in remesion now and is pulling through it better than I ever could!! ...thanks for asking

Pwood, I ordered the speedo gear set also, Im gonna change those when we do the gears.

Thanks for all the reply's, BTW heres a pic of my Formula!

Thanks again

 

Keith, happy to hear about your daughter. I am going to change to 3.73 on my trans am I am about to purchase. Please do post how much of a difference you get. Thank you

 

i loved the car much more after the gear change. no times, but a posi will make smoking the tires WAY more fun

 

I have the 3.73's with the 700R4 and originally had 2.77's. Needless to say, the speedo is way off I have checked with Dal Slabaugh at Van Devere about getting the correct speedo gear set for the tranny and he couldn't come up with anything above a set for about a 3.50 rear. Would some of you that have been there/done that please clue me into how to get my speedo reading correctly:hail:
Thanks in advance:rockon:

 

It depends on exactly what car and rear end but here's what I did. I have an '88 Trans Am with electric speedo and 10 bolt 2.73 rear (originally) and 245/50/16 tries. I switched to 3.73 gears. I had to install a 15 tooth drive gear and a 44 tooth driven gear and now the speedo is right on. They tried to tell me that I needed a new speedo sensor but all it is is just the original with the plastic tabs cut a little and then rotated 180* to accomodate the different driven gear diameter. IIRC I had to order the driven gear for an '86 because it was no longer avail in '88 for some reason.

Maybe this will help some. Good luck.

http://www.700r4.com/SpeedOCalc/

 

Well I got bad news today.... The Zexel-Torsen diff. is on back-order

Does anybody know where I can get a carrier somewhere else at a good price like SLP?

 

mines on backorder too. they said somthing about shipping it without some part or somthing...


Im also doing the swap, 2.73 to 3.73 with a 700R4.
I have 3.73's in my blower car. let me tell you, i can spin em at any speed at any time. it fishtail doing 80 MPH on the highway when i gun it. scary, actually.

 

Thanks Corey for the link you gave me:
http://www.700r4.com/SpeedOCalc/
I was able to determine that I needed a 15 T drive gear and a 44 T driven gear and ordered the gears from the same company (Bowtie Overdrives). I'm about half way through the installation and will have to wait now until my ruptured achilles tendon heals before I can get under the car again

 

How long did they say that the backorder was for on the SLP unit? Thanks!

 

anybody know how long?

 

criSSes - I actually just used that as a calculator. I tried calling them to order mine but they said they only carry the gears for a cable driven speedo. I just went to a dealer and knowing the info found the part numbers for what I needed and ordered it from them.

I had so many mix-ups to deal with by the time I got the right ones I'm not sure but these should be the part numbers for a 15 tooth drive gear and a 44 tooth driven gear for an electric speedo 700-r4. If you want to check at the dealer tell them you have an 86 T/A with a 700-r4.
008642620
025513051

When you get ready for the install you'll want to buy an extra one of the clips that holds the drive gear on too, it will probably break and it only costs like a dollar and some change. And get a wrench big enough to go around the output shaft to push the old gear off with.

I actually have the sensor that the dealer wouldn't take back new in box if anybody wants to buy it cheap, since I wound up not even needing it.

 

Corey - I have a cable driven speedo on my 89 IROC. Thanks for the info on the clip and how to get the old gear off.

 

I just purchased an eaton posi unit from http://www.gearsareus.com/ for 349.00 plus 18.00 shipping. Shipped same day. Seems like the best price around. he also carries other brands. check it out. Will let you know how car feels when i get it back hopefully today or tomorrow. Cant wait.

 

Dude!...Screw the car and the upgrades.
Take her to Disneyland.

 

Also doing the 2.73 to 3.73 swap. Try the classifieds on this site, I just saw a Auburn and Eaton unit for sale. Did you guys rebuild your original rear, or buy a used rear, rebuild it, and then put it in??? I want to buy a used one and rebuild it so that I can drive my car whild I'm working on the new rear. Problem I'm having is finding a new rear! Never thought it'd be this hard! I also don't know how to tell if a 10 bolt has a 26 or 28 spline axles without taking it apart. If someone could please help me figure out how to tell what is inside a 10 bolt I'd really appreciatate it. I'm buying a Zexel posi unit for 28 spline, but need a rear with the correct axles. Thanks in advance. Good luck on the buildups, and congratulations to you, Keith27, and your daughter!!!