Trans Question

85foxman · Dec 6, 2012

I pulled the engine and trans out of my 85 GT to freshen up gaskets/seals and clean everything up. Well after some inspection of the trans (speedo don't work) it has no speedo gear inside the trans. I've done some searching, and please let me know if I'm wrong, the speedo gear is dependant on the rear gear ratio? If so, that means I gotta find a 2.73 speedo gear or a T5 from a car with the same rear gear as mine? I'm really new to the mustangs technical info so I apologize if this seems like a stupid post. Any info or tips on how to go about fixing this issue would be great. Thanks in advance.

Boydster · Dec 6, 2012

Yes, you need a different speedo gear for different rear gears.

There's 2 gears... the drive gear that goes inside the trans on the tailshaft, and the driven gear that goes on the end of the cable. Here's a link to Latemodel Restoration. They'll have whatever you need for whatever trans and whatever gearing.

http://www.latemodelrestoration.com/Product/List?keyword=speedo gears&vehicle=Mustang&year=1985

Boydster · Dec 6, 2012

Also, here's the chart that shows which gear you need for what rear gears and trans. Note however that they do not list a 2.73 for a mid-80's 5 speed... the lowest they show is an 18 tooth for a 3.08. However there is a 17 tooth for an 83-95 manual 5 speed... I believe thats the one you'd want.

http://www.latemodelrestoration.com/item/LRS-17271I-K/83-95-Mustang-17-Tooth-Speedo-Gear-Kit-Manual
http://www.latemodelrestoration.com/page/Mustang-Speedometer-Gear-Application-Guide

85foxman · Dec 6, 2012

I'm looking for the gear in the trans. Is there a way to tell my rear gear? I was told 2.73 by previous owner who lied about almost everything with this car. I just wanna make sure of the rear gear before I order parts. Thanks for the info boydster.

Exile · Dec 6, 2012

85foxman said:
I'm looking for the gear in the trans. Is there a way to tell my rear gear? I was told 2.73 by previous owner who lied about almost everything with this car. I just wanna make sure of the rear gear before I order parts. Thanks for the info boydster.

Ive never herd of 2:73 gears, but 3:73 gears are pretty much the most popular gears out there. Whether the guy you got the car from might of been lying to you about it or not, are you sure he didnt tell you 3:73 gears instead of 2:73 gears?

85foxman · Dec 6, 2012

He told me 2.73. I thought the same thing. How can I check my ratio? Is there a way to check it without opening the diff?

Exile · Dec 6, 2012

85foxman said:
He told me 2.73. I thought the same thing. How can I check my ratio? Is there a way to check it without opening the diff?

Jack up the car, get under it to put a reference mark on the bottom of the drive shaft facing the ground, and have a friend spin one of the tires one complete rotation. While your friend is doing this watch the number of times the drive shaft spins, and that is your gear ratio. So if you have 2:73 gears your drive shaft should spin 2 3/4 complete rotations.

88LX5.Oh · Dec 6, 2012

Exile said:
Ive never herd of 2:73 gears, but 3:73 gears are pretty much the most popular gears out there. Whether the guy you got the car from might of been lying to you about it or not, are you sure he didnt tell you 3:73 gears instead of 2:73 gears?

You've never heard of THE most common factory installed gear set for fox bodies? Interesting...

Mustang5L5 · Dec 6, 2012

2.73s are the stock standard gear for fox Mustangs.

When you say there's no speedo gear in the trans, do you mean on the cable? Or inside the transmission?

If you don't see the one inside the trans, the clip holding it probably broke. The gear is probably inside the trans, but you'll need to remove the tail housing to install a $1 clip

85foxman · Dec 6, 2012

Thanks for the info! That's good to know. The gear on the cable seems fine, I can't see or feel a gear at all in the trans.

Mustang5L5 · Dec 6, 2012

If you shine a flashlight up the speedo gear hole, you should see a plastic worm gear. If you see the metal shaft, then most likely the clip broke and the gear walked down the shaft.

Tail housing needs to come off to fix it

Sent from my iPhone 4S using Tapatalk

85foxman · Dec 6, 2012

I seen a YouTube "how to" video on this, the guy makes it out to be somewhat of a chore to do. What kind of job is this to do? Is it difficult to do? How long should it take to do?

Gearbanger 101 · Dec 7, 2012

Before you buy anything, ask yourself.....do you ever plan on switching the rear end gears from the stock 2.73's, to a gear set higher than 3.73:1 (or anything higher than 3.27:1 for that matter)?

If so....I highly recommend you buy the 6-tooth drive gear, over the 7-tooth. The stock 7-tooth will allow you accurate speedometer readings up to a 3.73:1 gear ratio. If you go any higher (numerically) than that, you'll need to have a 6-tooth drive gear in there to remain accurate.

Mustang5L5 · Dec 7, 2012

85foxman said:
I seen a YouTube "how to" video on this, the guy makes it out to be somewhat of a chore to do. What kind of job is this to do? Is it difficult to do? How long should it take to do?

Well, someone who's experienced with T-5's can probably do it in the car. You'd need two people as well since there are some tasks that require driving a roll pin through the shifter block while pulling the tailhousing off.

First time? Take the trans out of the car and put it on a bench. Then it's pretty easy.

Page 14 is where you would need to begin reading

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