Swapping Rear Gears....what speedo gear?

[Spdrcer34]

I can't find a website that has the info I need...

I am swapping rear ends, from a 3.27 Open (code 41), to a 3.73 Limited Slip (code D4). I have the Mazda 5spd transmission, and I am running 285/50-18 (29.27" tall) tires in the rear.

What gear should I have in there NOW, and what gear do I NEED to get?

Thanks in advance,

Ryan

 

[boominXplorer]

4:10 i think

 

[Robb]

4:10 i think

I don't think that is a speedo gear option.

You need to pull your current gear and see what you have, then work from there.

 

[boominXplorer]

ah i thought he was asking opinion on what gears like everyone else and their brother

 

[Creager]

you should have a 16 tooth speedo gear. it should be offwhite/greyish in color

you will need either a 17 or an 18.

you will have to get a couple sizes to figure it out exacly what works. im gonna say you need 18.

 

[Spdrcer34]

Thank you guys!

Ryan

 

[Spdrcer34]

.....okay, ASSuming I do have a 16T gear (I honestly haven't had time to check for sure)

I checked my speed via someone pacing me, AND via my tach....

Both ways, my speedo says I'm doing 75-76mph, but I'm REALLY doing 65.

Using the equation on TRS, New Teeth = (Current Teeth x Speedo Reading)/Actual Speed

(16x75)/65 = 18.46
----OR----
(16x76)/65 = 18.70

Should I get a 18T gear, and show a little MORE mph? Or get a 19T, and be a little slow?

Ryan

 

[Creager]

.....okay, ASSuming I do have a 16T gear (I honestly haven't had time to check for sure)

I checked my speed via someone pacing me, AND via my tach....

Both ways, my speedo says I'm doing 75-76mph, but I'm REALLY doing 65.

Using the equation on TRS, New Teeth = (Current Teeth x Speedo Reading)/Actual Speed

(16x75)/65 = 18.46
----OR----
(16x76)/65 = 18.70

Should I get a 18T gear, and show a little MORE mph? Or get a 19T, and be a little slow?

Ryan

get them both and see which works best. i think they are like 3 bucks a peice.

 

[Spdrcer34]

.....nope, they are 8.50/ea. Sold in a 2pk! How ridiculous is that.....so that's 17.00/pk......that's why I wanna know which one I should get, if it were $3/ea. i wouldn't care, and buy both.....but doing it YOUR way, I'd be paying $34.00!

Ryan

 

[Maniak]

Find another dealer.. They don't have to be sold in 2 paks.. I've bought them two different times (once for a tire size change, once for gear changes).. I can't remember how much they were (they were pretty cheap) and I bought just one. Both Ford Dealers in town were willing to sell me just one.. (I chose the dealer closer to home).

~Mark

 

[Creager]

Jesus man! 8.50 EACH!?

I paid less then 8 bucks for two, and i got a 19 tooth gear and a 21 tooth gear haha.

Some of them are reverse cut. The guy at the dealership wasnt sure which one i needed, i bought the wrong one at first.

 

[Spdrcer34]

Alright, I'll try the 2 other dealers in the area.

I know one of them uses the same 'network', and the other one doesn't.

Ryan

 

[Spdrcer34]

...okay....so I procrastinate a bit too much....

But I finally got the speedo gear out of the X, and found that it is an 18 tooth gear.

Here's the set-up again,

STOCK________________NOW
28" tire (235/70-15)_____29.22" tire (285/50-18)
3.27 Open Rear Gear_____3.73 Posi Rear Gear
M5OD R1 trans__________M5OD R1 trans
18T Speedo Gear________xx Speedo Gear

I have tried to figure this all out....but I can't seem to come up with the right answer to what speedo gear I now need.

Ryan

 

[ma96782]

Read this:

http://www.explorerforum.com/forums/showthread.php?t=154152

Aloha, Mark

Here are some sites you might like for tire and gear calculators:

http://www.4lo.com/4LoCalc.htm

http://4wheelparts.com/4wp/assets/!..._gear-ratio.htm

http://www.1010tires.com/TireSizeCa...p?action=submit