The Stovebolt Site Forums The Parking Lot Big Bolts Driving a 2 speed rear

I was wondering if someone could explain to me how to drive a 2 speed rear in a 41-46 truck. I know how to drive a non-syncro transmission but the 2 speed rear has me confused. Also, what is split shifting?

51 Ashton (Mike) has tried to teach me. If you are not carrying a heavy load, you might be able to leave it in high-speed range?

yes, as Tim says, unless you're quite heavily loaded the rear shift isn't useful, but with a load, start in low/low, shift rear to high, then to 2nd/low, then 2nd/high, etc - the rear gives a range change in each gear, so effectively you have 8 gears and can keep engine RPM in the 'sweet spot', most useful with a diesel

Bill

I have 2 speed rear ends on both my '50 COE and my '47 Diamond T. I find them very useful, as I drive my trucks in low mountain country. For example, to go to town I drop from 6250 feet to 5300 feet in about 7 miles. Going to town the rear is in high and coming home in low, whether I have a load or not. Of course, at the altitudes I drive I lose power anyway (my engineer friends tell me I lose about 3% horsepower for every 1000 feet. When you are underpowered to begin with, it really makes a difference).

The only time I need to split shift is with a heavy load uphill (such as July 4th when I picked up Lightholder and 26 of his friends at Whiskey Row at 2 am in the COE and brought them home). Now that was a load of loaded lads and ladies.

Kent

We never split shifted a 2 speed unless we had a heavy load. In fact, 2 speeds shift much easier with a load than when you are light. We simply started in low range, went through the gears and when we were tached out in high gear, we shifted the 2 speed into high range, let off the gas while holding the stick with 2 or 3 fingers. You can feel on the stick when the rear has completed the shift. Then gently give it gas and it should be in high range. If you hit a small incline, you can shift the axle into low, let off the gas momentarily and then gently give it gas and you should be in low range for increased pulling power. Once you have topped the incline, shift her back to high range like you did previously. The lower the gear you are in, the harder it is to shift the 2 speed properly. Learn how to shift in high gear first and then try it in a lower gear. Split shifting is shifting the transmission into a higher gear while shifting the two speed into low range at the same time. Or shifting the transmission into a lower gear at the same time you shift the 2 speed into high range. Master shifting the axle in high gear before you try anything else. In the real world, we always started an empty truck in low range and stayed in low range until we got into high gear. Back in those days we considered someone who shifted the 2 speed on an empty truck a kid who had just learned to drive, and this sold a lot of planetary gears for Eaton when they screwed up.

I use my 2 speed diff all the time even on flat ground and with no load. My 46 has the vac. control and you don't even touch the clutch to shift the diff.. It's great for going around corners, I just leave it in high and down shift the diff.. It shifts smoother than the trans.

This is going to be a "working" stovebolt because I plan to be hauling 2-ton of coal with her to heat my home in the winter and since I will have to cross over mountains she has to pull up some steep grades.

So are you guys saying when I'm driving I can shift LO-HI on the fly? If your doing a haul like what I described would you go 1L-2L-3L-4L---then shift 1H-2H-3H-4H OR 1L/1H-2L/2H-3L/3H-4L/4H??

Mongo"s garage has a cool factory sticker I got for $10. showing the speeds to shift at and even shows the exact vac. switch that the 46's have. It is 1st L-H 2nd L-H 3 rd L-H 4th L-H. Google Mongo's grarage I just found a picture of the sticker in their catalog,they have like 4 items total

That's awesome, I'll have to order one! Just curious what MPG would you think I'll be getting "empty" and "fully loaded" in this beast?

My owners manual says 45 MPH governed speed. That's about what I get with a new 62 235. My wrecker is always empty.

What kind if miles per gallon have you experienced with your truck?

I've never checked, but I'm sure it's way down in the single digits. If you don't have a owners manual for your truck you should get one. One 1940 manual has all the info. for all trucks, factory tire sizes, diff ratios, a lot of info. I've spent a lot of time paging through mine and there cheap through any vintage parts dealer.

My '56 weighs in at just under 10K with just me in it, tooling along at 55-60 it got a little over 9MPG on a fairly flat route. Add a load and some hills, it's hard to say what to expect. Best bet is to do some testing.

like ken says, master shifting to hi range first. that should take about 3-5 shifts at most its that simple. down shifting is just as simple however after all these years i still mess up on occasion but not to the point that i slam it into gear just slightly delayed. its like everything else its just timing and when your not paying attention you screw up the timing. on occasion i split because i have to. due to where i live and what i sometimes haul i have to shift the rear in lower gears. its funny how it sounds in the lower gears working then in the higher gears.

I have found that shifting up and down is way easier when the truck is under load, if it's free wheeling at all it's a pain in the neck to shift it right.

Like others have said I shift from a dead stop from 2L, 3L, 4L, 5L then 5H. For the most part, after I get in High Rear, I stay there until I stop again. Pulling a long grade going up hill I'll up and down shift the rear, but coming down hill I down shift the trans so I don't get the rear hung up between high and low letting me free wheel.

Mike B

I have found that shifting up and down is way easier when the truck is under load, if it's free wheeling at all it's a pain in the neck to shift it right.

Like others have said I shift from a dead stop from 2L, 3L, 4L, 5L then 5H. For the most part, after I get in High Rear, I stay there until I stop again. Pulling a long grade going up hill I'll up and down shift the rear, but coming down hill I down shift the trans so I don't get the rear hung up between high and low letting me free wheel.

Mike B