recommended speed

Unknown

There is a lot of talk about axle ratios etc, What is the maximum recommended cruising speed for a stock 47 Commodore 6? I usually drive between 50 and 60. 48,000 miles on engine, no rebuild to my knowledge. I've never been faster, I hate to open her up to see how fast she'll go and tear something up major in the engine, when I never go that fast anyway.

Unknown

I don't know the axle ratio. It doesn't have overdrive. It's dark now so I can't see, but how do I determine the ratio? Are there numbers somewhere?

Unknown

Oh yeah, the tires are 6.50 16.

Jon B

The high speed rearend ratios were rare so you probably have the 4.11 rearend. I'd keep it at 50-55. If you want to drive long distances at a higher speed, I'd invest in an overdrive transmission, which will give you better mileage and lower RPM's at speed. With an overdrive I think you can safely cruise at 60 with little spurts at higher speeds. I have retro-fitted an overdrive to my '37 (which has the same engine you do) and that's the speed at which I drive on long trips.

Unknown

I wonder where one would find an overdrive? I look on E-Bay daily and can't recall seeing one. They are probably pricey however and with the poor economy I probably can't afford one.

Uncle Josh

Jack up one rear wheel. Mark it and rotate 2 turns and count the revs of the drive shaft. Should either be 4.56 or 4.11

Unknown

I believe the ratio for the 46/47 cars without overdrive was 4.11 and with O.D. was 4.56. The pickups were 4.56. I put a single lever trans with O.D. in my 47 pickup and changed to the 4.11 pumpkin from a car. The trans was from a 51 or early 52 stepdown as the transmission case had a casting date on it of nov-- 51 The transmission bolted right to the 47 bell houseing. The drive shaft has to be shorter and the stepdown trans & o.d. is longer than the 46/47 you have to pull the engine to get the transmission. But it sure did slow that engine down at 60/65 mph

[Deleted User]

coreywalker wrote:

I don't know the axle ratio. It doesn't have overdrive. It's dark now so I can't see, but how do I determine the ratio? Are there numbers somewhere?

To find your rear ratio, do it the old fashion way, takes 2 people. Jack up one rear wheel and install a safety jack stand under that axle housing but make sure the other wheel in still on the ground. Now have someone slide under the car with a white chalk and put a line on the drive shaft and a matching line on the housing, then you put a line on the floor and a matching line on the tire. Now the person under the car will count the number of drive shaft turns while you slowly turn you tire 2 full turns and stop at your chalk marks. Now have him tell you how many turns the drive shaft made right to the fraction. If you have 4:10 ratio it will be 4 turn and 1 tenth of a full turn. 4 turns and a little over a half more then you have 4:5/9 ratio. Walt.

[Deleted User]

Why not just clean the diff housing and read the ratio that is stamped on the carrier housing?

Park_W

Why not tell the fellow where the ratio is stamped, so he doesn't have to clean the whole thing! LOL. I agree it's almost certain to have the 4.11, which means he's turning about 3,000 RPM at a true 60 mph. I like Jon's recommendation to cruise at no higher than 55 mph until he gets an OD in there. Look in WTN classifieds and post a wanted note on this forum ... those ODs are out there, and typically can be bought for $150-200 max. Wire it like the '50 and later cars to keep things simpler and eliminate the need for the special relay originally used from '41-'49.

Lee ODell

The formula to determine engine speed (RPM) is: MPH X GEAR RATIO X 336 DEVIDED BY TIRE HEIGHT = RPM with overdrive multiply RPM BY .70 60 x 4.11 x 336 devided by 29 = 2857 RPM, with o/d 2857 X .70 = 2000 RPM

Hudsonrules

:)Hi Jon, I also have a '37 Terraplane, once belonged to Kelly Hindgardner{Terraplane Kelly}, It needs the clutch replaced and the opening in the floor is to short to remove the transmission as it has overdrive. I cut a peice of the floor out and am still short about an inch. Is it posible to move the engine forward about an inch to have the transmission clear? I really do not want to have to pull the grille and radiator, as I just do not have the strength to do that work any more. Any Idea's, Thanks in advance. Arnie In NevadaJon B wrote:

The high speed rearend ratios were rare so you probably have the 4.11 rearend. I'd keep it at 50-55. If you want to drive long distances at a higher speed, I'd invest in an overdrive transmission, which will give you better mileage and lower RPM's at speed. With an overdrive I think you can safely cruise at 60 with little spurts at higher speeds. I have retro-fitted an overdrive to my '37 (which has the same engine you do) and that's the speed at which I drive on long trips.

RL Chilton

Arnie-



I know you referred this question to Jon, but let me chime in here.



There's no reason you can't slide the engine forward to gain your much-needed inch. However, since you do not want to remove the radiator, typical unshrouded fan-to-radiator clearance should be 3/4". You'd most likely need to remove at least the fan to gain the clearance and then be darn careful to don't run the water pump into the core of the radiator when shifting the engine.

Hudsonrules

:)Thanks Russell, I will be extra careful. Arnie

Unknown

Now, isn't it true that top gear on both a non-od and OD trans is 1:1. My assumption is that if you reratio your rear end, you might get back some low end torque with an OD. I've been looking at this myself for my 48 Super Six. My engine runs too fast at 60.



I have a 308, so I am told that all I really need is to re-ratio the rear end. The engine is powerful enough to get off the mark in 1st without an OD.



I'll have to see what my ratio really is, but I'm assuming the drive train is stock.



Anyone know of conversion kits for rear ends?



-Chris

nick s

usgrant7 wrote:

Now, isn't it true that top gear on both a non-od and OD trans is 1:1. My assumption is that if you reratio your rear end, you might get back some low end torque with an OD. I've been looking at this myself for my 48 Super Six. My engine runs too fast at 60.

I have a 308, so I am told that all I really need is to re-ratio the rear end. The engine is powerful enough to get off the mark in 1st without an OD.

I'll have to see what my ratio really is, but I'm assuming the drive train is stock.

Anyone know of conversion kits for rear ends?

-Chris

Chris, I think you don't understand the function of overdrive. 3rd in both transmissions is 1:1. OD drops the output .7 on the highway it would be the same effect as having a higher rearend say around a 2.87 assuming you have a 4.11 rear end (typ for non od car) now but you maintain the low end torque by being able to revert to the 1:1 output.
As far as converting your rearend, higher ratios for the hudson are hard to come by but if you have the spicer from a later car you can get dana 44 gearsets in say 2.72 but you will suffer under load. a later 3.07 rear out of a hydro car would be a better option and actually a little higher final drive than a od and 4.56 (as typical from the factory)
for perspective with a hydro 1:1 in 4th and the 3.07 rear i'd like another gear on the highway so at some point i'll build a 2.72 for it

Jon B

Arnie, I don't recall what Kelly had as a setup in that '37 but I suspect it was the 1940 overdrive, like mine. It is theoretically possible to remove the transmission with the engine in place but I was told that it was such a bear to get the shaft all lined up (it's soooo tight in there with that OD!) that it would be MUCH easier to just pull the whole thing out. Which is what I did.



Yup, it's a bit of a pain to remove the radiator shell (bigger pain to get it back on!) and the radiator, but once you do (and you disconnect all of the regular stuff) the whole thing comes out like a charm: engine, clutch and transmission. I did it myself using an old fashioned hand-operated hydraulic portable hoist that I rented for a day. Once the engine is out of there you can also do a lot of cleanup and even detail the engine compartment. And get in to make various adjustments on linkages, etc. etc.



Well, that's my two cents!

Clutchguy

The water pump on these cars-47 and earlier- are replaced after removing the housing in which they are mounted. Drain the rad., Loosen the clamps on the rubber hose for the water jacket and slide it back onto the water jacket,remove the lower hose,remove the 2 bolts located under the water pump housing and remove the complete assembly,fan and all. There is a small gasket that is used to mount this housing and the 2 bolts must be resealed also. The fuel hose/line,most of the coolant and the exhaust must be removed to move the engine forward only an inch??,might as well remove the grille assembly, pull the engine and slip just the engine out and leave the trans. You will have to support the back of the trans and leave the trans.mount bolted to the cross-member. I know this can be done with its standard trans but not sure with the '40 O/d on it?. Good luck



I wanted to add that the clutch disc has to be aligned perfect to accomplish this-preferably with a good input shaft.It should be aligned almost perfect anyway and/or it increases the chances of doing damage to the disc.

Rocket

Hi,

I have been watching this thread and I would like to know at what speed I could drive my car without hurting the motor an rear end. I have a 1936 Hudson coupe with 8cyl. with the electric hand. I'm hanging a overdrive unti with free-wheel on my carrier housing, am I taking a chance at possibly burning out my motor or rear end driving at today's highway speed.

Clutchguy

Rocket wrote:

Hi,

I have been watching this thread and I would like to know at what speed I could drive my car without hurting the motor an rear end. I have a 1936 Hudson coupe with 8cyl. with the electric hand. I'm hanging a overdrive unti with free-wheel on my carrier housing, am I taking a chance at possibly burning out my motor or rear end driving at today's highway speed.

Eight cyl.engine runs with alot less effort at 60-65 than the 6 cyl.. Adding an O/Dr.will make it much easier on the engine,and cause less wear for sure! Faster speeds in these cars are hard on brakes though. Make sure to keep them service and adjusted correctly. My dad has a '37 H-8 and it doesn't mind running at 60-65, seems effortless? Std.trans and 4:10 axle. Just my opinion.:cool: