I may have access to an Eaton two speed from a mid '70s F600-700 truck. I have the '45-'52 vacuum shift two speed that I saved when I sold my '47 COE. Is it possible to install the electric shift motor from the later axle on my vacuum shift axle? Or, will the center member from the later axle fit my earlier axle housing? I probably won't do anything until I get my truck on the road, but I am thinking that I might need the two speed to be able to split my gears to keep the RPMs in the torque band of the diesel. I believe 1st and 2nd on the Brownie are too far apart in ratio to work well for splits. Besides, the little I've driven, I can see that I am not going to be very good at split shifting with two sticks. The Brownie will be great for the overdrive though. Any thoughts?
Thanks, Mark

 

Hi Mark,

I have an Eaton 1350 2-speed and I did remove the vacuum "arm" from it and installed the electric actuator and motor from a newer axle.

I am not sure about a MUCH newer F-700 axle though. The motor didn't change much in many years but the actuating mechanism did change a little.

You may have to get the parts side-by-side and compare.

Regards,


Rick

I probably should also add that the electric actuator was used over a wide selection of 2-speed axles. You do however need to have the correct "shift fork" that is actuated by the electric motor. I am not sure how much those differ over the models and years.

Mine looks like the following one on ebay
NOS EATON / SPICER 032678 SHIFT FORK ASSEMBLY S221 | eBay

 

Thanks for the reply, Rick. When I get a chance, I will go look at the mid '70s truck and check the axle out.
Mark

 

What axle ratio is in your F-4 now? Most F-4 seem to be equipped with the 5.14 gear set, while the two-speed axles are typically equipped with the 5.83 gear set.

Also, your aux should split the gears nicely using overdrive (1st, 1st over, 2nd, 2nd over, etc). Using the T-98 and 5531 gearing you get the following progressive ratios:
1st - 6.4
1st over - 4.61
2nd - 3.09
2nd over - 2.22
3rd - 1.69
3rd over - 1.22 (a nice "under" for when high gear is a bit too high)
4th - 1.00
4th over - 0.72

It all looks good on paper, I have no idea how hard it is to shift. This guy (start watching at 10:20) makes splitting gears with a 5531 look reasonably easy, but I know looks can be deceiving.

 

I am planning to use it with my automatic but I don't think I'll attempt to "split" gears. I don't think it's really possible with an automatic and probably not necessary anyway.

 

Thanks, Fred. I may be overthinking this. It may work fine as it is. My sticks are side by side, so they might be easier to split than his setup. I have the 5.83 axle now. The vacuum two speed I have has 5.83/8.11 ratio. Oddly enough, the difference in ratios on the two speed is .72, exactly the same as the difference between direct and overdrive on the Brownie. I just need to get it done and drive more.
Mark

 

Rick, The two speed will shift fine without a clutch. You will probably only use low range when starting a heavy load, and may not even need it then.
Mark

 

That's nice to know!!

I have never driven a truck with an Eaton 2 speed that I could shift "on the fly".... I thought I would have to have the clutch disengaged to shift the axle.

Now that I think about it, I seem to remember that, when UP-shifting, to a higher (axle) gear, you switch the axle, and then let off on the throttle momentarily (presumably to "unload" the planetaries) and the axle would just shift.

I'll just have to experiment!!

My automatic trans (E4OD) also has a 0.71:1 OD plus a locking torque convertor. I will have complete (electronic) control both!

With everything in "top" gear, and the 9.00-20 tires, I expect about 2100 RPM at 60 mph (flat ground, unloaded of course!!)

Cheers,

Rick