Jeep Speedo Gear? Really?

'88Cobra

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Oct 21, 2004

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Jul 14, 2008

#1

• Jul 14, 2008

• #1

So my car has 3.55 gears in the rearend, and my speedo is out. After doing a search I found that I need the 23 tooth white speedo gear that is apparently a jeep speedo gear in my tranny. But the info I didn't find is what jeep speedo gear do I need? Meaning what year of jeep? What model? And what tranny did it come out of? Any help please?

 

jrichker

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Jul 15, 2008

#2

• Jul 15, 2008

• #2

See Speedometer Chart for the proper gear. A 23 tooth gear isn't correct for 3.55 rear axle.

 

TRWXXA

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Jan 18, 2003

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Jul 15, 2008

#3

• Jul 15, 2008

• #3

Jrichker is right (as usual).

You probably need a 19-tooth (pink) or 20-tooth (black) gear for the 3.55s. You're leaving out info. You need to know your tire size, the number of drive gear teeth (we're assuming it's a 7-tooth (yellow) gear in your '88 T-5), in addition to the rear end ratio.

 

'88Cobra

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Jul 15, 2008

#4

• Jul 15, 2008

• #4

Oh, sorry. I am totally leaving info out. The T5 is for a '90 GT, not an '88. So it should have an 8 tooth drive gear. And the rear gears are 3.55's, and the rear tires are about 26.5" tall. So a 23 tooth gear should be right, shouldn't it?

 

TRWXXA

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Jul 16, 2008

#5

• Jul 16, 2008

• #5

'88Cobra said:

Oh, sorry. I am totally leaving info out. The T5 is for a '90 GT, not an '88. So it should have an 8 tooth drive gear. And the rear gears are 3.55's, and the rear tires are about 26.5" tall. So a 23 tooth gear should be right, shouldn't it?

Click to expand...

A 1990 tranny does change things.

# Driven Gear Teeth = 20.168114 / Tire Height (in.) * Axle Ratio * # Drive Gear Teeth

20.186114 / 26.5 * 3.55 * 8 = 21.6

A 21-tooth gear should get you to within a 3% speedometer error (discounting other factors), which is pretty good.

 

'88Cobra

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Jul 17, 2008

#6

• Jul 17, 2008

• #6

Okay, sounds good to me. Thanks for the help.

 

Mustang5L5

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Jul 17, 2008

#7

• Jul 17, 2008

• #7

Visually confirm your drive gear though. Being a 1990 t-5, it's had 18 years of history and someone could have changed the gear. A lot of guys tend to swap to the 7-tooth gear

Take the speedo and look inside. If it's yellow, it's the 7-tooth

if it's green----8 tooth

If it's black....6 tooth