The Stovebolt Site Forums The Parking Lot Big Bolts Help with eaton electric 2 speed rear end?

Hey yall, I just bought a 79 Chevy C60 Wrecker. 366 BBC, 5 speed, 2 speed rear, dual winches, dual swivel booms, etc. I know this site mainly focuses on pre 73 stuff, but I figure the good folks in the Big Bolts section will know a bit about the later big trucks as well. I'm a bit new to the 2 ton stuff, myself. My 1 ton is getting too beat down pulling heavy so I needed a bigger truck.

One odd thing about it is the rear end looks like it was possibly swapped. For one it's a 6 lug instead of the usual 10 lug or spoke wheel hubs I usually see on them. The 2 speed wires either weren't ever hooked up when the new rear end was put in or something went wrong with it and they snipped them. An IH Loadstar 1600 that a briefly had a couple years back had the same 2 speed box so I'm guessing it came in quite a few different trucks.

So which wire hooks up to what? There's 2 coming from the box and 3 coming from the frame, so I'm guessing one is a ground? I've tried having a touching the wires together while my friend flips the switch to see if I can hear it shift. But I guess I need to figure out which is the ground before that does any good.

Also, right now, I'm not sure which gear the rear is in right now. It currently tops out at an honest 60 mph give or take a few so I'm guessing high. That sound about right?

Onto some photos of it.

Red Wrecker front

Red wrecker rear. Holmes 500 bed

20's. 9.00R20 fronts with the normal 10 bolt wheel on 5 lug hubs like every other MD chevy I see.

22.5's. 11-22.5's. 6 lug

2 speed box. Looks like the typical eaton 2 speed box to me?

Diff. Does that rear end look factory?

Other Misc pics of the truck.

Interior

Shifter

Engine bay

366

I guess that about covers it. Any help would be appreciated.

I dont remember that electric 2 speed drive in GM's but we used a world of them in IHC's. I always liked them better then the vacuum shift. You are right it probably is in high. I will look at some books tomorrow & see if I can find a scematic on it.

Eaton 2 speed on the IH.

Here's the 2 speed from the 70 IH Loadstar I had. It's most definitely the same 2 speed box but the axle itself seems to be different. For one it has a bolt on inspection cover intead of the solid pumpkin on the Chevy. The picture is all I have of it and it appears to have a loom dropping down so I can't tell what wire goes where from it.

IH Loadstar diff

Here are some pages from an International service manual that covers the Eaton 2 speed shifter. It is for 1950-53 years...but I believe that the information should be the same anyway.

http://i299.photobucket.com/albums/mm311/jungerfrosch/linked/Eaton2speedshifterpage1.jpg
http://i299.photobucket.com/albums/mm311/jungerfrosch/linked/Eaton2speedshifterpage2.jpg
http://i299.photobucket.com/albums/mm311/jungerfrosch/linked/Eaton2speedshifterpage3.jpg
http://i299.photobucket.com/albums/mm311/jungerfrosch/linked/Eaton2speedshifterpage4.jpg
http://i299.photobucket.com/albums/mm311/jungerfrosch/linked/Eaton2speedshifterpage5.jpg
http://i299.photobucket.com/albums/mm311/jungerfrosch/linked/Eaton2speedshifterpage6.jpg
http://i299.photobucket.com/albums/mm311/jungerfrosch/linked/Eaton2speedshifterpage7.jpg
http://i299.photobucket.com/albums/mm311/jungerfrosch/linked/Eaton2speedshifterpage8.jpg

Hope this helps....I know some of the pictures are hard to see, but they should be good enough I hope.

Tad

Eaton used the same electric shift box on all trucks that used an electric shift until they went to an electronic switch. A 366

Eaton used the same electric shift box on all trucks tThe black is low, red hi, and green is ground. A 366 should run faster than 60 in 5th in hi axle unless it was governed for that because the speed limit in 79 was 55 all across the US. It looks like you have New Process which is a close ratio between 4th and 5th.

It might go faster than that. The speedometer is all over the place over 55 so I don't know how fast it actually goes.

Anyways, thanks for all the help guys. Much appreciated.

Edit - really got to wind the truck out today and according to my friend following behind me, I got it up around 75 or so running against the governor in 5th. The speedometer was reading 65...

That's with 42" tall 11-22.5 tires and whatever odd rear end is in the truck.

I would like to thank jungerfrosch for posting the books for the eaton. I searched all kinds of sites look and trying different things! This was the one that worked and made the most sense!!! THANKS AGIAN

i know this is a perfect example of thread necrophilia but i have a 70 c60 that until last week was gutted of a shift switch and wring harness i built my own harness and found a switch in a junkyard i wired it up thanks to information found here and it works beautifully with one minnor flaw the shift motor does not shut off is this normal or am i missing a relay somewere any help is greatly apreciated

Take the shift box apart. They had a bad habit of accumulating water. There is a good chance that the limiting switch is stuck or the ajax screw is galled. The old style Eaton Box was the same from the 50's until about 1985 and parts are still available.

i believe its my limit switch i am a little confused as to what flips and retracts the switch my sitch is in good shape just a little sticky

Here is a picture of the shift box and photo 2 is a wiring diagram.

https://plus.google.com/u/0/1126369...6836972546&oid=112636930370126476644

In this illustration the limiting switch is called the automatic switch. The part they call the drive screw is what shifts the axle. The electric motor is reversible and when the block reaches a certain point it breaks connection in both directions. The shifters were bad about collecting moisture which damaged the thread on the drive screw and the often the bearing at the bottom got rusty. Eaton used this same electric shift assembly until about 1985. I have my best luck finding NOS electric Eaton parts that were originally sold by Ford. There were a lot of Fords around and they didn't fool around with the vacuum shift that GM used for so many years. International is also a good source because they also used electric and a lot of little towns had an IH dealer.

i think for some reason it is not tripping the switch in the shift assembly i took it apart and cleaned it of all crud and replaced it with fresh oil it shifts beautifully but i think the problem is in the switch what exactly is suposed to trip that thing

Anyone know whether the Eaton electric shifter would fit the old vacuum shift 2-speed rear end?

Hello Day !, Check out your post on the Old GMC website.

Like Spanky said, read what we posted on the Old GMC site. Your code S-7544. These two pages are the information I cited on the GMC site.

https://plus.google.com/u/0/1126369...3451166626&oid=112636930370126476644

You will have to find a shift fork for an electric box in order to change from either air or vacuum on an Eaton 17500.