3.73 gears

[lincoln log]

I'm thinking of puting 3.73 gears in my mark VII and I was woundering what I could do about the speedometer speed difference that will occur. I've heard that I need to replace a gear on the speedometer cable but, I know nothing about it. Where do I get one of these gears and how do I install it. Also, do 3.73 gears perform well with the mark VII or not?

[KULTULZ]

There is a Speedometer Gear Usage Chart in the FORD RACING PARTS CATALOG that will give you the needed application along with a formula if you use odd size tires, etc.

The driven gear choice also depends on the drive gear (trans output shaft) you have-either 7 or 8 teeth. Seven teeth is the more common in which case you would need D0OZ 17271-B (21Teeth and color coded purple) available from your FORD dealer.

[Lscman]

Gears install easily on the speedo sensor. I know there's a limitation to the matching due to the gear installed on your AOD trans tailshaft. I believe 3.73 is the maximum possible ratio you can correct with a huge 23 tooth driven gear. Steeper gears require a tailshaft gear replacement (trans removal). Sorry, not sure due to brain fade.

[lincoln log]

so, should i get a 21 tooth or a 23 tooth?

[pro-five-oh]

For the 3.73s you'll need the white 23 tooth unit. This will clear it up: http://www.steeda.com/store/-catalog/speedometer.htm


Losing the 3.08s/3.27s in your Mark will kill your highway mileage and crusing ability. If you are prepaired for that, then you might want the 4.10s for maximum kick. Where's Stinkin Lincoln (Forrest) when you need him to prove a point???

[ November 14, 2001: Message edited by: pro-five-oh ]

[Lscman]

The number of speedo teeth required = (new axle ratio/old axle ratio) x # teeth on old speedo gear.

[ November 14, 2001: Message edited by: Lscman ]

[lincoln log]

Thanks lscman, for clearing that up. With 3.73 gears, how bad can I expect my gas mileage to be?

[ZGR8MK8]

Lincoln Log-
I have a brand new set of 3:73's I never used. Email me at mtx12@optonline.net if you are interested.

[lincoln log]

I may be interested lscx. Does anyone know aprox. how many mpg i would loose by going from a 3.27 rear to a 3.73 rear?

[RODDMOD]

A friend just had the 3.73 gears put in he wishes he had done the 4.10 setup. ;)

[Calvert92LSC]

Just some "heads-up" info. Motive Gear is offering a 3.90 gear for the 8.8 now. I can't beleive it took someone this long to manufacture this.

[Lscman]

Your highway mileage will drop from about 23 to 18 or 19. City mileage won't change much.

[Charlie]

Will he really lose 4 MPG going from a 3.27 to a 3.73??? Wow, I wanted to change my 3.08 to a 3.27 but, maybe I won't. I get about 23 Highway now.