The Ford Barn

len47merc · 07-15-2014, 07:45 PM

Another vote for the 3.78 over the 3.54. My stock '47 Merc has 3.78 gears and is peppy around town and 'torquey' enough over 45 mph to climb the hills, foothills and mountains here in central and western NC, not only to hold speed but accelerate up most hills when necessary. Were the (vast) bulk of the driving done on midwestern flat lands or the flat Piedmont and coastal areas here in NC the 3.54 might be preferred. Ideal set-up is 3.78 with a Columbia overdrive unit to be able to comfortably set interstate paces (if needed) while keeping rpms around 2,200 in OD. In the meantime, while capability currently exists to run 70 mph with this stock set-up, am comfortable running 60 mph max to preserve the car and keep motor compartment noise associated with higher rpms minimized.

GEOFFNZ · 07-16-2014, 03:14 AM

If you look at vehicle weight the post war Fords were considerably heavier than pre war versions.Combine that with a high diff and the extra power of the bigger motor was more than sucked up.We had a '46 Mercury with a 3.54 diff and although a good cruising car it just didn't have it on the hills compared to a '37 or '38 on 3.78 gears.I always felt it would have been better on 3.78.Cheers

07-15-2014, 07:45 PM	#21
len47merc Junior Member Join Date: Dec 2013 Location: North Carolina, USA Posts: 21	Re: 3.54 rear gear in 46 to 48 convertible Another vote for the 3.78 over the 3.54. My stock '47 Merc has 3.78 gears and is peppy around town and 'torquey' enough over 45 mph to climb the hills, foothills and mountains here in central and western NC, not only to hold speed but accelerate up most hills when necessary. Were the (vast) bulk of the driving done on midwestern flat lands or the flat Piedmont and coastal areas here in NC the 3.54 might be preferred. Ideal set-up is 3.78 with a Columbia overdrive unit to be able to comfortably set interstate paces (if needed) while keeping rpms around 2,200 in OD. In the meantime, while capability currently exists to run 70 mph with this stock set-up, am comfortable running 60 mph max to preserve the car and keep motor compartment noise associated with higher rpms minimized.

07-16-2014, 03:14 AM	#22
GEOFFNZ Senior Member Join Date: Jun 2010 Location: Oxford New Zealand Posts: 177	Re: 3.54 rear gear in 46 to 48 convertible If you look at vehicle weight the post war Fords were considerably heavier than pre war versions.Combine that with a high diff and the extra power of the bigger motor was more than sucked up.We had a '46 Mercury with a 3.54 diff and although a good cruising car it just didn't have it on the hills compared to a '37 or '38 on 3.78 gears.I always felt it would have been better on 3.78.Cheers