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What speedo gear do I need?

thcscubajohn

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M5od r1 non HD ratios. 3.73 final drive. 35" tires. Is there some sort of chart or something that'll tell me which gear I need?
 


RonD

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Yes, you can go here: https://www.tciauto.com/speedometer-gear-calculator

Gear on the output shaft has 7 teeth, this is the DRIVE gear
ratio 3.73
Tire 35

Comes up with 15 tooth driven gear
Not sure they make them but someone might, Fords only go down to 16 tooth

I think you can get replacement DRIVE gears for the M5R1, an 8 tooth drive gear would put you up to a 17 tooth driven gear.

Sorry, you have a transfer case, so DRIVE gear is on the transfer case output shaft, and yes you can get 8 tooth drive gears for those
You need to remove the drive line and flange from transfer case and remove seal, then slide the old 7 tooth gear out and slide the new 8 tooth gear in
Then a new seal and replace flange and drive line

The flange NUT can be a bear, 150+ ft/lb torque spec, and not all sockets fit it, 30mm thin wall
 
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Shran

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I'm pretty sure they do not make 15 tooth driven gears. I just ran into this with one of mine... the speedo reads 5mph slow after swapping a manual t-case in and it has a 16 tooth driven gear. Curious if maybe my old t-case had a higher tooth count drive gear than the new one perhaps. Anyway I looked and looked and never could find a 15t driven gear.

3.73's and 35" tires sounds awful, I bet your clutch is very unhappy with that combo.
 

thcscubajohn

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31x10.50r15
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Yes, you can go here: https://www.tciauto.com/speedometer-gear-calculator

Gear on the output shaft has 7 teeth, this is the DRIVE gear
ratio 3.73
Tire 35

Comes up with 15 tooth driven gear
Not sure they make them but someone might, Fords only go down to 16 tooth

I think you can get replacement DRIVE gears for the M5R1, an 8 tooth drive gear would put you up to a 17 tooth driven gear.

Sorry, you have a transfer case, so DRIVE gear is on the transfer case output shaft, and yes you can get 8 tooth drive gears for those
You need to remove the drive line and flange from transfer case and remove seal, then slide the old 7 tooth gear out and slide the new 8 tooth gear in
Then a new seal and replace flange and drive line

The flange NUT can be a bear, 150+ ft/lb torque spec, and not all sockets fit it, 30mm thin wall
Ok. So to confirm, I need a 8 tooth drive gear and a stock driven gear? Is the drive gear a BW part or ford?
 

thcscubajohn

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31x10.50r15
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Smog is for pussies.
I'm pretty sure they do not make 15 tooth driven gears. I just ran into this with one of mine... the speedo reads 5mph slow after swapping a manual t-case in and it has a 16 tooth driven gear. Curious if maybe my old t-case had a higher tooth count drive gear than the new one perhaps. Anyway I looked and looked and never could find a 15t driven gear.

3.73's and 35" tires sounds awful, I bet your clutch is very unhappy with that combo.
Its got a spec unsprung hub and ~ 330lb ft at the crank. I wanted 80mph@2000rpm for mpg purposes. The clutch is just gonna have to live with it.
 

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80mph at 2k?! Good god...
 

thcscubajohn

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31x10.50r15
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Smog is for pussies.

RonD

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Yes, 8 tooth drive gear and 17 tooth driven gear, not sure what your stock driven gear is

Might need to call around I didn't see any BW1354 or 1350 8 tooth gears come up
1345 and 1356 did but I am pretty sure they had larger output shafts
 

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Its got a spec unsprung hub and ~ 330lb ft at the crank. I wanted 80mph@2000rpm for mpg purposes. The clutch is just gonna have to live with it.
:headbang: So what engine mods you got goin on there???
 

RonD

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35" tires and MPG?????
 

thcscubajohn

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FORD
Engine Type
4.0 V6
Engine Size
247ci
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4WD
Total Lift
4"
Tire Size
31x10.50r15
My credo
Smog is for pussies.
:headbang: So what engine mods you got goin on there???
 

thcscubajohn

Active Member
Joined
Nov 23, 2014
Messages
147
Reaction score
31
Points
28
Location
Antarctica
Vehicle Year
1994
Make / Model
FORD
Engine Type
4.0 V6
Engine Size
247ci
Transmission
Manual
2WD / 4WD
4WD
Total Lift
4"
Tire Size
31x10.50r15
My credo
Smog is for pussies.

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