What gears and diff is everyone running?

FineLineMtrSprt

Registered User
Just wondeirng what gears some of you guys are running. I know i used to always see the IRS 8.8 center section in the Ford Racing catalogs and they would say dont go over 3.27's or the case may warp or something. Also what type of locker are you guys running. Stock Traction Lok's or Auburns,powertrax?..Just let me know.
 
Never heard of not going over 3.27's.. Maybe they mean that for the aluminum diff?

I just ordered a set of 3.31 gears for my 5 speed SC. Here's what I am going with:

Starting out with a spare supercoupe cast-iron pumpkin
Motive Performance 3.31:1 AX series lightweight gearset
Ford Motorsport rebuild kit
Ford Motorsport IRS seal and stub bearing kit
Ratec solid pinion spacer (upgraded alternative to crush sleeve)
Trickflow carrier cap stud kit (replaces carrier cap bolts, much stronger)
Ford Motorsport track lock rebuild kit, using alternate clutch stacking method
F-150 S-spring for more preload.

I'm setting the gears and doing everything myself. Shouldn't be too hard, and I already have a press. This should be a nearly bullitproof differential, with quality parts and it will cost me less than $400

Jeramie
 
If it was recommended not to go over 3.27's in the aluminum case, why did FRPP sell them equipped with 3.73's? I have two of the 3.73/Trac-Loc/aluminum case FRPP centersections, and I haven't had any problems with them.

3.73's are a good gear for the auto SC's, and 3.27's are a popular choice for the 5-speed SC's. I'm currently running one of the FRPP 3.73 centersections in my 94 Splitport LX, and a 4.10/Trac-Loc setup in my DOHC 90 XR7.

-Rod
 
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I dotn know..i just remember it saying something to that affect. I was just wondering. Ive heard of some guys running 4.30 gears in the V8 MN12's...so i was just wondering what the popular set-up was on sc's
 
I always wondered about that caveat. I just assumed it was because of the increased driveshaft speed given the issues these cars have with driveshafts and even stock gears.
 
For the Supercoupe, I think most 5 speed guys will go with 3.27:1 rear gears, which is an upgrade from the stock 2.73:1 The dragstrip guys seem to like 3.08 because they can come out of the quarter mile in 3rd gear. Late model 5 speed transmissions had a bit taller gears, and those people can use 3.55's without being overly aggressive.

Most 89-93 Supercoupe Automatic cars upgrade to 3.73:1, as they usually have 3.27 standard.

Most 94-95 Supercoupe Automatic cars upgrade to 3.55, as they have the wide ratio transmission. They come standard with 3.27 or 3.31 depending on production date.

Hope this helps,

Jeramie
 
I've got 3.73s in both my cars. The 91 has the stock trac loc that was rebuilt when installing the gears and the 93 has an Auburn Pro. I tried 4.10s in the 91 when it was running mid 12s and picked up a couple tenths on the track, but I didn't like them on the street and quickly switched back to 3.73s.

David
 
I plan on running 3.55's when I get my center section rebuilt. Granted I don't drive a SC, I drive "one of those V8 cars". :D Most of the V8 guys recommend the 3.73's. I've been told that if I use 3.55's the only thing it'll do is make me wish I had 3.73's. But I do a lot more highway driving than I do drag strip driving, so I'll settle on the 3.55's.

Can't wait for the warmer weather so I can get them in. (I hate having to work outside.)
 
I am having a rear section built with 3.73s and a trac-loc carrier, it should be all done by this monday. I don't like having a open diff in a vehicle with a lot of torqe.
 
I will be going with 3.73 as well in a 92 auto. You need them to get these cars moving. Also, a really good seat of the pants feel too.
 
Well, my 95 has 3.08's which I find work well both at the track and on the street.

The 94, which doesnt' see the track, has 3.31's and I find that sometimes it seems like too much gear for the street. Both are 5 speeds. Seems like this comes down in many respects to personal preference and how you drive. Tire size too. I am runing 16" wheels on the 95 but 18"s on the 94.

Ira
 
I'm debating between 3.73 and 4.10 for my auto SC. I would gladly give up the gas mileage for a faster 1/4 mile so I'm probably going to get 4.10.

In my 5-speed I have 3.27 and I like them on the street.
 
I would never run a spool on the street....again. Ive done ti before in stangs and in street cars back home in Chicago..but in a daily driver..."I" wouldnt.
 
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