OKAY-- now some more questions (speedo gear)

[kbillan]

SO my new car-- i swear has 4.10 rear end. But now i am reading that for 3.55, 3.73, and up will use the 21 tooth gear.

SO-- because i clearly have a 21 tooth gear, my miles are reading wrong-- my speed is reading wrong.. etc...

I guess im wondering how wrong-- as I calculated the car having 4.10's based on an online gear chart... Maybe theyre 3.73? and the speedo is just off?

In you 1993 cobra, with 3.73's-- what does your speedo register at 60mph? Does your speedo bounce?

Keith

 

[red95gts]

First you need to find what the gear ratio is. Jack up the rear of the car and use a piece of tape to mark one of the tires at the 12 o'clock position. Crawl under the car and mark the driveshaft. Put the trans in Neutral and rotate the tire one full revolution exactly. Watch the driveshaft and count the number of turns to figure out the gear ratio.

Your trans has an 8-tooth drive (the one inside the trans) speedo gear. So, the formula would be:

Gear Ratio x 8 x Tire Revolutions Per Mile / 1000

For example (assuming 3.73s and a 245/45/ZR17):

3.73 x 8 x 811 / 1000 = 24.20

So, you'd need a 24 tooth driven gear, which doesn't exist.

You could pull the trans apart and put a 7-tooth drive in and then you'd need a 21 tooth gear, which does exist.

Tirerack.com is a good place to find revs per mile for each specific tire. Or, you could measure the distance your car rolls in one tire revolution and divide that into 5280, I guess. Might be slightly more accurate, but probably not necessary.

 

[kbillan]

Did this yesterday afternoon-- Counts out to 3.75 roughly.. so i am assuming this is a 3.73 rear end..

Wish the damn speedo didnt bounce. LOL. One of these days i am going to have my wife go out and pace the car with her car..

 

[red95gts]

If you have a portable GPS you can throw in the window, that works great for figuring actual speed.

 

[670 of 4993]

your speedo probably bounced because its missing some teeth. My car shreds speedo gears haha.

 

[kbillan]

your speedo probably bounced because its missing some teeth. My car shreds speedo gears haha.

thats great news!

The bouncing is quite annoying.. Ill tare into it today perhaps...

 

[kbillan]

at 60MPH or 65MPH... what does your tach read?

 

[Kevins89notch]

Did this yesterday afternoon-- Counts out to 3.75 roughly.. so i am assuming this is a 3.73 rear end..

Wish the damn speedo didnt bounce. LOL. One of these days i am going to have my wife go out and pace the car with her car..

Well if its 3.73s, I would keep them. 4.10s are a little too much, but I love 3.73s. When I bought my 89 from its original owner, the first mod was 3.73s. Sure woke up my 100% stock 5.0! I've had them ever since, even now with H/C/I and 14psi, and still love them.

When I someday drop some gears in my cobra, it will be 3.55s. I had them in a mostly stock calypso LX 5.0 a couple years ago the loved them. They had a nice amount of pull from the line, but you were still able to use 1st gear in parking lots and such.

 

[kbillan]

Oh yah-- i had 3.73 in my LX convertible...

but to be honest-- i really wanted a stock car. Im 30 now, and have a family.. I was looking for a daily driver-- not a drag car LOL. I know, i know- Gears hardly make it a drag car. But the point was-- I wanted a stock car. My buddy has a car with 3.55 in it, and we may swap rear ends... we will see. My issue is that his car is beat on.. it has rust... etc.. MINE-- does not. LOL. Might just leave it as "good enough".. Might swap in 3.08 or 3.27 over the winter. Nuthins for sure.



I have been bitten by this mustang bug again--- BIGTIME. I am now thinking I need one of these in each color. LMAO.


one thing that sucks--- i just turned my garage into a GYM... LMAO... I have no idea where this car will sit all winter..
Keith

 

[kbillan]

Update!

Okay-- I actually talked to the cars previous owner-- before the last guy! Told me quite a bit about the car! Nothing bad, either.. which was a relief. LOL.


the cars tranny was replaced at 98k-- which explains why it is so crisp on a 100k mile car. OH-- and its a brand new Tremmec!! bonus!

This owner also installed 3.73 gears. So that is put to rest.

NOW-- i am going to tear into this thing-- but because the tranny was replaced, its a crap shoot to know what driven gear is in it? right? Is there a way to tell?

also--
Mustang Speedometer Gear Guide - Latemodel Restoration Supply
has 23 tooth gears, wouldnt that be better than 21 If i need a 24?? LOL... I guess the best thing to do would be to go out with my wife today and pace the car.. see exactly where it is speed wise.. then come home and check out which gear is in there...

perhaps i should look on tremmecs site?

KB

 

[red95gts]

It would depend what the transmission was replaced with. If it was simply rebuilt, chances are it's still got the 8-tooth in it. If it was replaced, it could have a 7-tooth. Hopefully it was just rebuilt as the Cobras have an upgraded transmission as compared to the standard 5.0 cars. It's basically a T-5Z with a 3.35:1 first gear.

The 23 tooth would be closer, but is not a Ford gear. IIRC, it's a mopar gear and has very thin teeth, which often break. This leads to a bouncy speedo needle at lower speeds. I have that same gear in my 3.73-geared car and it's just crap. When I eventually pull the tranny out for a rebuild, I'll swap in a 7 tooth drive.

 

[kbillan]

Its a tremec t-45 according to

http://blacksautomotive.com/vehiclePrint_noBG.asp?id=188

the place the previous, previous owner bought the car from!

what does that mean for me and my speedo gear LMAO??

Keith

 

[red95gts]

Unless they swapped in a 4.6L modular motor there is no way it's a T-45. I love it when car dealers know their product well. LOL

It sounds like they put a new T-5 in it. There should be a metal tag on the rear of the trans with some numbers. That may help you to identify what it is, but chances are it's got an 8-tooth drive gear.

 

[kbillan]

AWE CRAP-- now your going to make me crawl under the car NOW...

Keith

 

[kbillan]

OKAY== stamped on the side of the tranny

BorgWarner
13 52 066 919

Speedo gear is roached-- its a 23 tooth..Pulled it out for now-- going to order a few more.. I wonder if i could cut one of these myself in a better material? I have a CNC mill.. might as well put it to good use..

 

[red95gts]

That's just a casting number on the side of the trans. That same tailhousing can be used on many different transmissions.

There should be a metal tag bolted to either the tailhousing or top cover with some info on it. When you find that, this is a good site to use:

Identifying and Assembling a T5 5 Speed

If there's no tag, there's no telling what it is without taking it apart or at least taking it out of the car.

Good Luck!

 

[kbillan]

thats awesome. Ill keep my eyes peeled when i crawl back under. Im trying to locate a speedo gear loacally ATM.. on the phone with
P and J Speed Shop

who have done work on my past cars-- they got em, out the door I go..

Keith

 

[670 of 4993]

I used a white steeda speedo gear for my 373's. Its not the best but gets the job done. I say invest in a handful lol

 

[kbillan]

No tag that I can see from the bottom. I can tell you the internal gear is a yellow'ie orange color..

The gear i just got from P&J has thicker teeth! I know someone mentioned thin teeth- which my old gear had.. these are noticibly thicker-- and he said they had good luck with them.. no brand name or anything.


The bad news is== the SOB still bounces== F Me. 2 hours wasted LMAO

Keith

 

[Red Turtle]

It took you 2 hours to change a speedo gear?