Hemi rear end gear ratio?

I have a 53 Dodge with the Flathead six in it with the stock 4:10 gears. As most of you know these cars are screaming at anything above 65MPH. One of my rear leaf springs broke so a Hamber with a 53 Dodge with the 241 Hemi said I could take the springs and anything else that I may neeed. Did the hemi's have a taller gear ratio in the rear? My dad had a 55 with a 270 Poly that he said would cruise all day at 80-85MPH.

 

yes, different engine/trans combos had different standard gear ratios. The closest ratio I have seen for that rear is 3.54 to 1. Best bet is to leave the rear ratio and change to an overdrive trans.

 

Yeah an overdrive would be awsome, but they are rare and exspensive. (this is practicly free) Iv'e heard that 3:55 is a good ratio for the six's. Does it say what the ratio is anywere on the rear? If this car doesn't have the ratio I want I will just by a Jeep Cherokee/Comanchee rear and flip the spring mounts.

 

Tom, I have a 55 Plymouth with a 241 poly. Head, three speed overdrive, 3.73 rear end and rear tires are couple of inch’s taller than stock. First gear is a bit to high but in OD it will run in the high 70’s real easy, I have no tach. and don’t want to push the old motor to hard, but on the highway it will keep up with traffic easily.




In 55 standard rear end for either the six or the V-8 with the 3 speed, was 3.73 and optional 4.10, with the 3 speed with overdrive it was the 4.10 and with the powerflite it was 3.73 for the six and 3.54 for the V-8. I am pretty sure the 53 would be the same. Maybe, see if you can find a rear end out of a powerfite car and swap it in, but I think that first gear may not be low enough.

 

Well I guess I will have to ask him if it had the powerflight trans in it. Right now the first gear in my car is pretty much ussless. I reguarrly take off in second no problem. In the owners manual it says you shouldn't exceed 24Mph in first and 48MPH in second. I've read in a few other threads that 3:55 is a good gear to have when running the flathead with no OD. Thanks for the info 55 Savoy. Did you find the ratio's on the net somewere? Or did you just know them from working on your 55.

 

Tom, the info came out of the 55 service manual. Just keep in mind that your flathead likes to run under 3000 rpm and the V-8's will easily do 5000 rpm.

 

Even with 3.73s your 6 will be a bit wound out. My '55 Ply has a 230/3speed with 3.73s. 55 is comfortable, 65 seems high but still managable(although I don't like driving at extended periods at that speed)

 

Ok, He said the car has a manual trans with the 241 so I guess they are the 3:73 gears. I've always heard that most of the old Flathead sixes had the 4:10 gears in them. How do I tell if I don't have 3:73 already in my car? Is there any numbers that tell me what gears it has on the housing anywere? I raced my friends truck once and had up to 85 and it was still pulling! Probobly not to good on it though. I'm only 19 so I like to push evrything to it's limits.

 

Tom, The easyest way to find out which gear set you have is to jack up one side of the rear axle (one tire off the ground and one on the ground), now mark the drive shaft and the side of the tire that is off the ground. Then slowly rotate the tire ( parking brake off, trans. in neutral, other three tires chocked well) one revolution and count the revolutions of the drive shaft, its not perfect but it will get you close. A little over four revs. of the shaft= 4.10's, three and three quarters revs.=3.73's, three and a half=3.54's and so on.

 

I tried doing this today and driveshaft only spun 2 times when I rotaded the wheel one turn. This doesn't make sense! Are you sur you don,t count half tuns or something? This is how I always thought you did it too. hmmm.

 

With ONE wheel off the ground, the driveshaft will spin HALF it's normal speed because of the way a differential works. You will either have to double your driveshaft count, or spin the tire around twice.

 

Thanks a lot Bugman, I figured that that was how it worked but just thought I would ask.

 

Sorry about that , I know better

 

Glad I could help (55 Savoy, you sould see some of the stupid stuff I've posted over the years )

 

I have 2 - 54 dodges both are royals one is a 4 door and other is a indy pacecar. both powerflites ... I checked the rear end gear ratio on both and came up with 3.54's on both. Your system to check an open gear ratio works great . Thanks bugman !

 

...did anyone notice that the thread is 8 years old...hhmmm.....

.

 

Yes, but I looked anyway as you did! Gary

 

well ...I finally got under the 54 dodge royal to check the numbers on the rear end. here is a pic. I don't see any numbers relating to a 354 gear ration. unless they are in code.
these numbers were on the drv side side of case . NO numbers on the pass side of case .