51 merc needs a little speed up

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oldsman41

Senior Member
getting tired of the cussing and the one finger salutes im getting from the a holes im on the road with. im sure they think im doing 60 in a 70 mph zone just to peeve them off but the merc is stock motor and 3 speed od. 60 seems where it wants to be,about 2050 rpm. what i like to know from the gurus here is can i go to a different rear gear and not tear the clutch out of it when starting out in 1st.its got the 4.11 in it now. or am i baby it to much at the lower rpms. she seems very content at the 2050 rpm. tires are 235 75 15s thanks in advance.
 
I dont think 2050 is any problem at all. 2500 isnt an issue either. Stick to two lane roads or put your foot in it....... Mark
 
You won't hurt it. Those engines are made to run. I'm older and gentler now but used to run my '50 75 - 80 mph all the time on the open highways of Nevada. Still run my F1 70 on the interstate. (T5 trans with 20% overdrive and a 3.78 axle.)
 
oldsman41 said:
getting tired of the cussing and the one finger salutes im getting from the a holes im on the road with. im sure they think im doing 60 in a 70 mph zone just to peeve them off but the merc is stock motor and 3 speed od. 60 seems where it wants to be,about 2050 rpm. what i like to know from the gurus here is can i go to a different rear gear and not tear the clutch out of it when starting out in 1st.its got the 4.11 in it now. or am i baby it to much at the lower rpms. she seems very content at the 2050 rpm. tires are 235 75 15s thanks in advance.
Click to expand...

I have a 49 Merc O/D transmission with 4.11 gears and 30.5" light truck tires on the Tonner and usually cruise at 65 MPH in O/D turning about 2200 RPM. As near as I can tell I'm right on or very close to the engines torque curve in O/D at that speed which is where you want to be. IMO you could easily push your Merc to 65 or 70 MPH without stressing the engine. The engine isn't the limitation for driving at that speed - it's the brakes... Drive the Merc where you feel comfortable and if the freeway saluters don't like that, they can use their passing gear.
 
Run it on up to 70. If the car handles fine and there are no warning signals from the engine you won't hurt it. We would like to see a picture of your Mercury.
 
My stock '47 with an 59AB, BW OD and 15" Merc wheels loves doing 60 or 65 but doesn't mind 70 or +. It just has that sound and torque feeling at its sweet spot.
 
Even though that Merc is a bigger and heavier car, I can't see a problem at running 23-2400 rpm. Flatties love a challenge! I do not think your od is much different than my avatar with a 5 speed. At 2500 I am doing 75. 23-2400 should put you right at 70 and hopefully getting more thumbs up vs the middle finger pointing skyward!
 
Most stock 1951 Mercs that had overdrive transmissions, came with the Dana 44 rear axle with the 3.91:1 gears. The next lower ratio was the 4.27:1 and it was for hill or mountain country. If a person wanted to pull the long long trailer then they would need the 4.55:1 ratio. The number on the little metal tag back on the rear case cover will tell the story as to the ratio installed when new.

The standard gearing would easily do 70 mph all day long. It may be that the car has the hill country gearing.
 
I feel like you're floating a golden raft in a sea of turds. If you got your car up to 70 then someone doing 80 would be pissed. People trying to cut 5 minutes off a twenty minute trip will never be satisfied, and will always arrive only 30 second sooner than if they did the limit anyway. Folks keep moving to my little town for the scenery and peace and quiet and then rush all over the place running stopsigns, and giving me dirty looks for going 30 in a 30! Thanks, legal weed and Google! Best thing to do in my opinion is to feel sorry for those that cant afford the extra time in their lives, drive your fully taxed and registered car however you want to within the laws and then give them a big smile and an emphatic "thumbs up". Angry drivers seem to really, really, hate that lately, it's been quite fun.
- Chris, Driving slow in Boulder
 
thanks guys. i couldnt find a tag on the rear end so last night i jacked it up and turned the rear wheels yeah its probably a 4.27 it goes 4 and a quarter turns on the drive shaft. i think i will look for a 3.91 or just kick it up a little on rpm.
 
You might call Randy at Randy's Gear Supply. I think new R&P sets are available for the older Dana 44 axles in more than a few ratios. They would be the same basic axle as the F1 pickups had in the 50 through 52 years and on into the early F100 series. The Dana 44 had the 6 5/8" ring gear bolt circle in the 1951 model year with 19 spline axle shafts. If you use any ratio smaller than 3.92:1, you will have to change the carrier to a smaller bolt circle design. The overdrive Mercs like that ratio. Smaller ratio will get the rpms down but might make it lug in low gear. The smaller ratios were for the Merc-O-Matic drive. I wouldn't go any lower than 3.78:1 myself but then I'm perfectly happy with the OEM 3.91:1 ratio. If you find an early Dana 44 out of an F1 pickup, it would likely have the 3.78:1 ratio but may have a 3.91:1 too.
 
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