Rear Axle: Top Cruise Speeds Question

[MikeK]

I am planning on driving my '55 E-12 from NJ to RI for the Meet in Warwick at end of June...I have only driven locally without getting on any hyways. I understand this truck may not be a speed demon so I am curious as to what the avg cruising speed is...I have the Original V8 224ci 2bbl carb , 3 speed trans w OD and Timken rear axle with a 4.857 ratio.

with the speed restrictions i need to plan my aprox 6hr route avoiding interstates.

TY Mike K

[Swifster]

So when you've been driving the truck, what speed are you at when the RPM's are at 3000-3500? May need to hook up a tach. Before interstates, the happy zone was around 45 MPH. If you are around 3500 RPM's and doing 50 MPH, or even 4000 RPM's at around 55 MPH, you should be good. If you can do 55, stay in the right lane. Most interstates have a minimum speed of 40 MPH (no, I'm not suggesting that). But running thru large urban areas (hello, New York?) the max speed limit is usually 50 or 55.

[StudeRich]

I am thinking that little short stroker is going to be really spinning at 55 MPH with probably 4.88 Gears even in Overdrive.

I have never seen a 4.857 listed in the Studebaker Truck Parts Catalog, but if you had your druthers, a 4.09 would be ideal.

[JoeHall]

Looking at your truck, tire size, OD, and rear end ratio, I'd think 55-65 MPH, all day long, no problem whatsoever. It will be interesting to hear your speed and MPG when you get home from the trip. Hope you'll keep us posted.

[PackardV8]

If your rear axle is in fact 4.85, then in overdrive it would be 3.50 and the engine would cruise all day at 65-70.

FWIW, I have a '55 E12 with 4.10 rear gear and after several miles at 60 MPH+ and 2800-3,000 RPMs, it would begin to experience the well-known Stude V8 problem at extended highway cruise, the oil system puts more oil in the rocker covers than can drain back down. Eventually, the oil level in the pan is so low, the oil pump begins to suck air.

Since yours will be turning considerably lower RPMs, just watch your oil pressure gauge and should it begin to drop, pull over for a rest break and let the oil drain back into the pan.

jack vines

[jclary]

I have never, in over forty years of driving it, looked to see the rear gear ratio of my E-5 six cylinder 1955 Truck. However, it originally did not have an overdrive. I added one in 1979. I never changed the rear end...so my truck has an overdrive with a non-overdrive rear end. I lose a good bit of speed on steep hills. In 1984, I drove the truck to the international meet in Florida. Once I got a few miles past Columbia, where the land really flattens out, I used my hand throttle almost like cruise control. My wife and daughter followed me in another car. My interstate cruising speed averaged between 65-70 most of the way.

I would be awfully disappointed if I had a V8 truck and it couldn't make better cruising speed than a flat six. Perhaps you could find another ready to bolt in rear end with a better road speed ratio. If you are like me, you would rather it roll freely down the road than chug pulling a load. Not that there is anything wrong with using a Studebaker truck to pull a load, but, our Studebakers have earned their rest. Rams, F150's, and other "upstarts," are there to pick-up the slack.

[greyben]

Some years back I owned a '52 Commander with 4.55 rear end and OD. It had no problem cruising at 75 on the highway. I'm sure you truck could do the same. The main concern with a pickup would be encountering a situation requiring sudden braking or evasive maneuvers at that speed. It can become very interesting.

[MikeK]

Swifster TY I am aware of all the restrictions which is why I have to look at this ...I dont have tach and speedo doesnt work since this truck was converted before I bought it to 12V ..i have a good app on phone and found I can do about 12 mph in 1st 25Mph in 2nd and the engine sounds like it is running hard at 50MPH in 3rd ...so it does look like 45 is max cruising comfort zone. prob goin to take Lincoln tunnel head up west side then choose a parkway or two (Henry Hudson , Cross island , Saw Mill to Merrick in Ct then rt 6 to RI)...I do Know my roads as I travel them all often on MC.

[MikeK]

The E12 3/4 ton came w/ either 4.11 or 4.857. the E5 and E7 came w/ 4.09 4.27 or 4.55

[MikeK]

John TY ...its a big learning curve...it runs fine around town and local roads ...and from traveling on MC Im used to stopping every 1.5 hours do to needing fuel ..so if it takes all day I'll be fine with it probably just tired when i arrive. I really plan on going so i can learn whats needed to do and its so much easier when the truck is right there. Also I will be down your way end of June, Looking to Retire to Greenville Area, need to check things out and see realtor.

[MikeK]

So you all know...My cable is broke for overdrive. I was told the cable only takes it out of OD. also there looks to be a switch that goes to a solenoid of some sort i believe is attached to trans. Not sure if this needs to be on or off.

[PackardV8]

So you all know...My cable is broke for overdrive. I was told the cable only takes it out of OD. also there looks to be a switch that goes to a solenoid of some sort i believe is attached to trans. Not sure if this needs to be on or off.

Getting the overdrive working will transform the truck. If it were mine, that would be the first priority. Even without the cable, if the selector is moved into OD, nothing else need be done to have it work automatically.

That's assuming the PO didn't do something to kill it. The OD is so important, difficult to imagine the PO not repairing the cable and keeping it functioning.

jack vines

[SScopelli]

If you want a cool calculator, I created one that takes transmission ratios, differential ratios and tire sizes, and calculates engine RPM per gear at a given MPH.

You can compare up to 4 rear differentials and 2 transmissions.

In this example, 215-60-15 tires with 4 different differential ratios.

At 75 MPH in 5th gear for T1, I can see engine RPM is 3046 with a 3.583 Diff..
Yes, I would never got to first gear at 75 MPH, but nice to know I can go to 4th or even 3rd if I needed to scoot and not blow the engine..

With a 4.54 ratio, and in 5th gear, engine RPM with T1 is 3860, 4th gear is a good downshift, but not 3rd..

The areas in Grey are values you can change.



(this is just a snap of the calculator..)

It requires MS Excel and PM me with email if you would like it.

[StudeRich]

That is a way cool calculator, but WHERE did you come up with those weird Axle Ratios?

Certainly not Studebaker, but also no other make I have ever heard of either! Good thing they are changeable because the only common one is 4.54!

[SScopelli]

That is a way cool calculator, but WHERE did you come up with those weird Axle Ratios?

Certainly not Studebaker, but also no other make I have ever heard of either! Good thing they are changeable because the only common one is 4.54!

Not Studebaker, but hopefully you have heard of Toyota.. Gears among the Rock Crawlers, and dare I say Drifters, hence going from 5th to 3rd!