I have heard so many positive things regarding putting 3:73 gears in my automatic Mustang. I was going to by some and have my garage install them. This is the description of the ones I was looking at. Are these what I should buy? Is $159. a good price? Here's the description:

3.73 Genuine Ford Racing Mustang 8.8" Rear End Gears Ford Racing # M-4209-F373N

Replaces M-4209-F373. New manufacturing technology utilizing a Face Hob Process which features a single pass pinion tooth machining operation compared to a conventional three pass process for machining. CNC cut and lapped gear teeth. Higher strength and better quality gears are produced with the Face Hob Process. Note: These new gears look a little different, the gear teeth are cut on a different angle and the ring gear has a bevel on the back of the gear.

This kit comes complete with the Following:

- 3.73 Ring & Pinion Gears M-4209-F373N
- Ford Pinion Shim Kit
- Ford Pinion Nut
- Ford Crush Sleeve

These will fit any Ford Vehicle with a 8.8" Rear end.

These Are brand New and in the Box!!!

Thanks

 

Sounds like a good price for Ford parts. Let us know how they work out.

 

I'm just not sure how much difference you're going to get going from 3.55s to 3.73s. It's a decent amount of work for a .18 ratio difference. I'm thinking a gear change needs to go to 4.10s and since this motor has torque everywhere, I'm inclined to just leave the 3.55s where they are.

 

ah hem 4.10's

 

Typo...fixed it

 

Automatic rear ratio is 3:31. He will see & feel a big difference.

 

Ugg...it's late, I missed the auto part. You're right, that's worth the switch.

 

OK but is this the item that is for my car and is the price good? What should I expect to pay to have them installed?

 

Upgrading 3.31 to 3.73 would be similar to upgrading 3.55 to 4.10. Taking an automatic all the way to 4:10 would be a big jump but I think I've seen someone else on here whose already put 4:10's in an automatic. Might be worth tracking him down and getting an opinion. If I had gotten the automatic I was going to go to 3.73's myself.

 

Bill....you'll be rockin and rollin REAL FAST with that gear change, are you sure you want to do that? I like mine just how it is, and like the top end on the highway......no shorter gears for me. :notnice: I may slip a shift kit in the tranny though.....

 

I need some clarification. The 05 manual GT has 3.55s and the auto GT has 3.31. How would someone correct the speedo if the software is not available. I had this problem with my auto until saleen flashed my PCM.

 

I had 3.73 gears put in my 95gt vert. purchased gears through buyfordmotorsport.com (I think, or it may have been gefracing.com) gears and install kit was about 130 (2 years ago). make sure you get the special ford gear install lube. Install cost, was about 200. made a big difference in my 95 gt 5spd. my installer did order an install kit from summit racing for insurance because the car was older and he didnt know how the shims and other small parts would be. with your car basically new, you likely will only need the parts you ordered.

Sam

 

Well, that's a pretty good price for the gears. I paid $189 for the same part # in '99. Think about it like this, though.... how much are you paying for those gears to be installed? My gear swap for my '98 was free, 'cause the diff had to be rebuilt anyways and I knew the parts guy (thus the gear swap), but had I not had the work done under warranty, it would have cost me an easy grand to do it through the dealer. I went up a full bean too, from 2.73 to 3.73... my point is, if you're going to be shelling out a lot of cash for a gear swap, why don't you make a significant change.... a change that you'll feel was worth the cash. It won't cost anymore to go up to 4.10s. ..... 'sept maye $20 for the gear set. I wuld be affraid of swapping to the 3.73s then being disappointed with the results.

 

The software IS available from any of the SCT dealers.

 

I think 4.10 should be the gear of choice in these cars, regardless of transmission type. The car has taller tires than the 99-04 models, so a 4.10 will equate to about a 3.99 gearing in the older cars.

The auto has that nice deep OD fifth gear; I would think the 4.10 would still be very comfortable for cruising on the highway. I had 4.10s in my 2001 GT and loved them...I would either go 4.10 or higher or leave the stock gears alone.

 

I recently had my 4.10 gears installed for my auto GT. You will love them if you like: Quick 1st-3rd runs and lots of Power and Torque.

Pop over hear and read about my 4.10's:

My Cat Domain Webpage

Io hope this helps. If you have more direct q/a - PM me.

 

Sorry for straying off the subject, but I am not too familiar with the differences in acceleration and top end the gears would make, based on the 3.55's (stock, manual) compared to the 4.10's. Could someone break this down for me please?

Thanks in advance.

 

Related item: I recall hearing (prior to the release of the 05) that the 05 measured speed by rotations of the rear wheels, NOT by rotations of the drive shaft. This meant that you could swap gears and not affect the speedo.

Can anyone confirm this? Where is the speedo pickup on the 05? It sure makes sense to move it to the axle instead of the drive shaft, that way only tire height changes would affect it.

 

armyguy,
Welcome to the forum. Books have been writen on the subject of gearing, but I will try to do it in a couple of sentances. The rear-end ratio is a reduction ratio. This means the high the number, the more turns the driveshaft must make to make the tires turn over one time. The result is, if you raise the ratio number (i.e. go from stock 3.55 to 4.10), you get more torque (power) and more acceleration but lower top speed. If you lower the number (i.e. go from stock 3.55 to a 3.31) you will raise your top speed but you will have slower acceleration.
Lots of other factors are involved but that should give you an idea.
Stay safe!

The Boss Hog

 

How much would the top end be reduced if you go from 3:55 to 4:10?