3.25 rear

4

42merc/ma

Junior Member
Thinking of relocating to Florida. I own a 42 Merc with 3.78 rear, thinking of going to 3.25. What kind of a job is this and will I be able to get the right gear for the speedometer? Thanks.
 
It might use the same speedometer gear as '31 Model A. If so,try Berts (303) 293-3673 or Bratton's 301-253-1929.

Charlie Stephens
 
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19Fordy, I was thinking about getting the Getz gear set from Speedway. Maybe 3.54 would be better, I am not sure. Looking for better cruising speed.
 
I didn't know anything with a number lower than 3.54:1 was made in that time frame. 1942 probably had the two part rear drive with the coupling but the earlier Mercury cars had a one piece drive shaft pinion combo. It made those early ones a bear to work on.
 
42merc/ma said:
19Fordy, I was thinking about getting the Getz gear set from Speedway. Maybe 3.54 would be better, I am not sure. Looking for better cruising speed.
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Here is an earlier thread about this subject. Living in FL I can honestly say that a 3:54 ratio will be just fine. Very few hills. If you do decide to make the change keep us posted and take plenty of pictures. Where in FL are you moving?
http://www.fordbarn.com/forum/showthread.php?t=40039&highlight=getz+gear+set
and
http://www.jalopyjournal.com/forum/showthread.php?t=283472&showall=1

Type the words "how to install getz gears in a banjo rear end" into your Google box.. Lots of info pops up from guys who know what they are doing that you will enjoy reading.
 
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Have you actually checked the ratio on your '42 Merc? Most all '42 Mercs were equiped with 3:54 ring & pinion gears with a coupling for the driveshaft.
 
Hey 42merc/ma You never mentioned what body style Merc you have? I keep track of most of them out there, and I don't think I have you listed. Did you move to Fla? I could put you in touch with the 42 Merc owners down there. Would like to talk to you or email. servantofthelord9-13-09@hotmail.com Even if you don't have the car any more, I still would like to talk to you about 42 Mercs
 
The best ratio would be the 3.54. If you have the 28 tooth cluster gear in your trans you'd have to slip your clutch too much every time you started out from a stop. Even the 3.54:1 ring and pinion benefits from a 29 tooth cluster gear. We sell many 3.54 gearsets compared to the 3.25 set.
 
Yes, 3.54 with 750 x16 rears is plenty adequate. This will put you at around 2500 rpm at 60mph.

Will this be true of a 42 Ford 6 cylinder, 3 on the tree, 650 x 16s with 3.54 gears?
 
No you will be revving a bit higher by having 6.50s instead of 7.50s. I haven't checked the original figure, but all else equal, the tyres are different.

Mart.
 
edhd58 said:
Yes, 3.54 with 750 x16 rears is plenty adequate. This will put you at around 2500 rpm at 60mph.

Will this be true of a 42 Ford 6 cylinder, 3 on the tree, 650 x 16s with 3.54 gears?
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The engine doesn't matter as far a RPM numbers go. It is determined (in high gear) by the rear axle ratio and tire size, regardless of engine type. As Mart stated the tire size will make a difference. Off the top of my head I think I remember it being about 200 RPM difference, but I could be wrong!
 
Here is an RPM chart from Summit for 60 MPH. You can find the tire diameters by going to one of the online tire suppliers, many of them list the diameters in their specification tables. The formula is MPH X Axle Ratio X 336 all divided by the tire diameter.
 

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I was hoping someone reading this post would know the trans gear ratios to know if mine was close or the same as 42 Merc/Ma. Merc what trans do you have in yours so I can look up the final drive ratios. Thanks
 
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