Need help with gears

1991blacksc

Registered User
Hey everyone, I am trying to squeeze some better times out of my 94 auto, I was thinkin next I should go with new gears. I drive it daily and race at the track for fun about twice a month. I was thinkin 4.10 or I heard 3.55 would be good. Also how hard is it to change them out? I am in college for auto mechanics right now so I have a good idea on what im doing so throw some guesses at what would be best:D
Also I am in need of down tubes and I was really lookin at the texas thunderbirds drag pipes, has anyone tried and do they boost performance at all? Thanks everyone, Matt.
 
well 3.55 or 3.73 would be best for your 94. You should also install a ford trac-lok in the rear since right now you have an open diff which only throws power to one tire. If you install a trac-lok it will make it limited slip and power both tires in a straight line.

Pull the axle shafts out, unhook the d-shaft, and lower the rear end pumpking down, the rest is standard if you know how to install and setup a ring and pinion set. I also recommend a set of polyurethane differential bushings that you can easily install while putting the pumpkin back in the car.
 
Kurt K had a post on installing or rebuilding the trac-loc.
I could not find the post. If you do a serch under Kurt K.
name you may find it.I think it had pictures with post.

RANDY
 
Gears

As far as which gears to choose it is totally up to you but I wouldn't waste my time or money installing 3.55's in a car that already has 3.27 or 3.31's. I think if the car is mostly stock I would go with the 4.10's but if you are making big power then the 3.73's would be the better choice. Whenever you install a trac loc in your car you don't need to do anything to the traction control just use it like you always have while driving the car around and turn it off at the track. I have been running the 4.10's in my car for the past year or so and have put around 20,000 miles on the car since installing them, it still gets around 22 MPG on the highway and runs much better than stock.

Charles
 
Charles
What would be the best height/width dragslick tire to use for 1/4 mile
drag racing. If using a 4:10 gear.with stock motor, AOD trans,
nonloc converter 2400 stall.I have big bakes on the rear so I
need to use 16 inch wheel or 17 inch.

Randy
 
Last edited:
Randy N Connie said:
Charles
What would be the best height/width dragslick tire to use for 1/4 mile
drag racing. If using a 4:10 gear.with stock motor, AOD trans,
nonloc converter 2400 stall.I have big bakes on the rear so I
need to use 16 inch wheel or 17 inch.

Randy

Randy I am using the Cobra rear brakes on my car and don't have any issue with a 15 inch wheel clearing everything. Of course I did the hub swap so I use wheel from a 99 up v6 Mustang and run 26X10 inch M/T slicks.
 
Charles
I was thinking of buying 27 to 28 inch high tires.
Because of the 4:10 being to low a gear for my set-up.
Do you think the 26 would be better?

Have you ever takin notice of your RPMs when
crossing the 1/4 mile finish line?

Thanks Randy
 
Randy N Connie said:
Charles
I was thinking of buying 27 to 28 inch high tires.
Because of the 4:10 being to low a gear for my set-up.
Do you think the 26 would be better?

Have you ever takin notice of your RPMs when
crossing the 1/4 mile finish line?

Thanks Randy

Randy if you think the 4.10's will be to low just install 3.73's instead. I don't think the 26 inch tire is better I just don't think a 27 or 28 inch tire is needed, at least not in my case as I don't have enough power to pull them. I usually shift around 5600-5700 rpm and go through the traps at 5400-5500 rpm and as you know that was with stock heads and cam.

Charles
 
Charles I have not done the math. To know what would
be the best size tire.I misplaced my notes during a move
into a different home. So I do not have the formula handy
to compute needed tire size.

I need to order tires for my car this week. To make sure
I have them for the shootout.

Thanks I didnt think 15" wheels would fit my car with cobra
size brakes on the rear.

RANDY
 
Randy N Connie said:
Charles I have not done the math. To know what would
be the best size tire.I misplaced my notes during a move
into a different home. So I do not have the formula handy
to compute needed tire size.

I need to order tires for my car this week. To make sure
I have them for the shootout.

Thanks I didnt think 15" wheels would fit my car with cobra
size brakes on the rear.

RANDY

Randy I can only tell you what works on mine, but unless there is something different about the offset on a T-Bird versus the Mustang wheel I don't see why a 15 inch wouldn't work on yours. Good luck at the Shootout, it doesn't look as though I am going to make so Connie will have to beat up on someone else in the final round this year. I have my hotel reservations and days scheduled for vacation but one of our supervisors at work just quite so that leaves two other guys and myself having to cover for his 12 hour shifts until we get another guy hired and trained.:mad:

Charles
 
Okay I am still really confused, Does my rear end already have trac loc and its not working or am I supposed to buy a trac loc diff or am I supposed to put the entire trac loc rebuild kit into my open diff and it will all work fine??? After reading alot I really understand how to rebuild the trac loc units but I found nothing on 94/95 open diffs. I think
Later, Matt
 
1991blacksc said:
Okay I am still really confused, Does my rear end already have trac loc and its not working or am I supposed to buy a trac loc diff or am I supposed to put the entire trac loc rebuild kit into my open diff and it will all work fine??? After reading alot I really understand how to rebuild the trac loc units but I found nothing on 94/95 open diffs. I think
Later, Matt


No your 94 auto doesn't have a trac loc, you will need to buy a trac loc diff and install it in your pumpkin along with new gears. Don't worry about the trac control as it will still work as it always has just a little better.
 
Now its startin to make sense:cool: would it be cheaper to buy an entire trac loc pumpkin with my desired gears? I have seen a couple people selling them on here for under 200 and I thought I saw them selling in catalogs for around 300-400. I think im gonna go with 3.73's. But will a trac loc pumpkin bolt right in and I will be able to use my same axles, driveshaft, etc?
Thanks, Matt.
 
Randy it seems to me that unless you are going to turn a lot more rpms a 4:10 gear is too much. With a 2200 stall converter I was at 5400 rpms at the end of the 1/4 mile. Would you want to go more rpms with a stock cam? You have a lot lighter converter then the one I was running at the time so wouldnt the engine wind up a lot quicker? Plus a mag3 ? Maybe if you had a tall enough tire? My guess is that you would be knocking at 6000 rpms at the lights. If you were having problems hooking up before you will blow the tires off with a 4:10.
 
That what I did, Just buy a complete built rear housing
with trac-loc & gears.

It was used with 4:10 gear new clutchs,spring.etc.
I was told it had 1000 miles on it. I payed $325.00
to my door.

The guy I got it from just used it to see, & try to
get the best time he could get from his bird.Then
removed them. I bought the 4:10 gear for one race.
Then I will be removing it and selling after the 06 shootout.

I plan to use the stock rearend housing and some parts.
To install in a MK-VIII aluminum housing with 3:73 gear.
Get this finished while using the 4:10 gear.

And yes the older style trac-loc will work just fine in
your ride.

Randy
 
Randy,

The 4.10 gears with 26" tires made my car quicker at the track and I think they are the best gear for racing an AOD until you start going quicker than low 11s or faster than 120 mph. At that point you need to switch to a 28" tire or 3.73s and keep the 26" tires.

David
 
Cool, now I think I got everything figured out. Now I gotta hunt for the perfect pumpkin:) . Thanks for all the help everyone, Matt Cool.
 
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