The Stovebolt Site Forums The Shop Area Engine Shop 2 speed axle problem??

Greetings folks,

Yesterday I took a '64 C60 (that I am thinking of buying for a restoration project) for a test drive. The truck can be seen here:
1964 Chevy C60

It has a 327 CID motor, a 5 speed tranny and a 2 speed rear axle. Suspension is rated at 22,000 GVWR. VIN is 4C623J156631.

OK...so I'm going down the road and everything is fine when the rear is in "low". I shift the rear to "high" and it felt/sounded like the truck was constantly popping out of gear...almost like the "high" side of the rear axle wasn't working or engaging. :confused: :confused: :confused: I shifted back to "low" and all was OK.

Now, while I have used 2 speed rear vehicles often, I've never had an issue with them and, as such, don't really know how to troubleshoot them. Is this a huge problem? Perhaps it is a vacuum issue? I don't suspect the tranny because it shifted fine and seemed to work fine. It really seemed like an issue whereas the axle was not "engaging" when I shifted to "high"?

Is there a way to better determine what the problem is? I can't do much other than visual inspections cause it is not my truck. However, I would like to know if this is a severe problem that will be costly to repair during the restoration process?

Any insight would be greatly appreciated

Burgy
Is this a vacuum shift? Or an electric. Seems kind of new for vacuum. Could be leek if vacuum, at axel/ diaframe. or if elect check shift box on axel, Little moter moves sun gear in and out, but also operates a knif blade switch that sometimes after a time does not let moter compleat the move of the sun gear,the switch also reverses the polarity of the moter to pull the sun gear out back to low gear. OR BAD ELEC SHIFTER SWITCH AT SHIFTER. First things first electric/ OR VACUUM ?

Burgie, it must be not shifting all the way into high. But you know that already. Has the truck set for an extended time? It shouldn't be a big deal if the rest of the truck is in decent shape. Mike

Thanks for responding so promptly

The truck is a couple miles down the road...so I'll go check it out and report back!!!

Thanks again

Hi folks,

OK, I checked the rear axle and it is definitely a vacuum based 2 speed. That is, there is a diaphragm on the axle pumpkin with 2 rubber tubes going to it. Those attach to 2 metal tubes that originate at the front of the truck. So, should I decide to buy the truck...what is the process of troubleshooting? I'll trace the lines to ensure they are in a good state of repair...but is there anything specific I should look for? Is there any way to disconnect the lines at the diaphragm and test the axle?

Any ideas would be appreciated!!!

Thanks, in advance!!!

I'm suprised it's vaccumm. Even my 56 Phord was electric. Think you need a manual to study. I may have one for late 60's or early 70's big truck, have to look. Heck, even the 55-1 GMC I had only had one vac line to it and big spring to return. If gears are worn or shot, big deal and $ to fix. If just a control problem, shouldn't be that bad. Checking all the rubber hoses would be start. Should be reinforced hose, not just heater hose or such on those. Also, the steel tubes will rust where they are clamped or pushed against frame spots. It's more a PIA problem really, Have Fun!

Hi GLPerry,

Well, I may be wrong as I've been wrong before :rolleyes: :rolleyes: :rolleyes: . However, there are 2 hoses that go to a diaphragm assembly...so I can only assume that is a vacuum controlled split rear. Although I saw the tubes inside the frame channel leading to the front of the firewall area, I did not visually trace it more than that. After all, it is not my truck and I don't want to make it look like I'm doing mechanic work on something that isn't mine. I'm just being courteous. I gotta believe it's something easy. The truck bed gives me the impression that it was well cared for and not "beat to snot". In addition, those rear axles are almost indestructible.

I would welcome the opportunity to borrow or receive a photocopy of any manuals that may apply to this particular vehicle. I can send you a PM with all my contact information if necessary.

Thanks for the info, in advance!!!

Burgie

Burgie, looks like a nice truck! Garwood bed too, I have a 52 4400 with the same dump setup and two speed rear that is vacuum operated. Works well and has two hoses like yours. If the engine is idling and you shift from high to low and back to high again, you should note that the engine revs will go up a little due to leaning out of fuel mixture and you should be able to hear the vacuum "whoosh" sound for just a second and then it stops. (This of course assumes you got a good mufler and valves are in good adjustment so you can hear over the engine noise)

If you hear a constant sucking sound in high range, but not low, you have a leak on the high range side of the diaphram.

Good luck!

Ken...and everyone,

I just got off the phone with the seller and we arrived at a mutually acceptable price. I'll be picking up the truck this Friday or Saturday. I also will use this project to hone my web skills as I will be setting up a website with pics, story line, C60 data, and anything else I can find. :rolleyes: :rolleyes: I browse other sites and gleen useful information from them...so I want to return the favor.

Now that she's mine, I'll be able to better look into the rear axle issue !!!

Thanks again and I'll be posting a URL in my signature once I get things setup.

Take care for now!!!

Yep vacuum shift was the standard way of doing it on these trucks, I'll bet it Looked like this, right? Check the lines for leaks and the vacuum valve uder the cab, also there will be some vacuum lines under the hood that feed to this setup. You may want to see if it is making vacuum. My guess would be in the line from the switch valve to the diafram in the hight side, it pul;led back into low Ok.

To test the high gear in the axle, remove the vacuum diafram from the rear axle and shift it manualy, if it still jumps in high gear, then the gear set is bad.

Or I just though of this, switch the hoses at the axle and see if high gear works now, and low is messed up.

Burgie, Did you decide to buy this '64 C60 instead of the '65 C60. The Chevy rear axles were vacuum shift where as the heavier Eaton rear axles used by Chevrolet were electric shift. The Chevy rear axles were rated at 15,000, 16,000 , & 17,000lb., the Eaton rear axles were 17,500, 18,500, & 23,000lb. ratings.

If the swapping the sides of the vacuum hoses doesn't change the high range problem, the clutch plate teeth and sliding gear teeth are worn off and kicking it back out of gear. If someone has driven it a lot and not shifted the 2 speed without letting it grind into gear, that problem happens. That sun tach on the dash, is a dead giveaway to the previous driver.

HEY! 46CHEV. What part of N.C. are you from.

Folks,

Thanks for the continued responses. I appreciate everyones inputs and knowledge. I will be getting the truck tomorrow afternoon...then it's mine . I have a long journey ahead of me and I'll be documenting everything I do on a website...so stand by :rolleyes: :rolleyes: .

OK, back to the possible axle issue. A few questions:

1. How do I identify who makes the axle? Is the a serial number? Casting? etc. that clues me into the manufacturer?

2. Is there a site anywhere on the web that details the inner workings of this type of axle? That is, something that shows me how a 2 speed axle works?

It is my sincere hope that this problem is something simple like a bad vacuum hose or a disconnected line :confused: ...but we'll have to wait and see.

Well, that's it for now. I'll be posting the URL to my new site once I get things up and running...

Thanks again, folks!!!

Burgie

Spanky, I'm from Lizard Lick. I know, never heard of it, it's near Raleigh,lol.

Burgie, There should be a I.D. plate located on the left kick panal below the dash. It will have the diff. type ,along with the gear ratio.

If you do end up needing any parts for that rear axle I know of a couple places to get them...
Trucks in Central Oregon

The yellow 62 GMC is in a steel salvage yard and due to be crushed soon but parts are cheap if I pull them myself.

The 60/61 and 64-66 Chevy's are at Bend Auto Recyclers in Bend, OR and priced decent for parts rigs ($300 & 400 each).

There is also a wrecking yard called Ira's in Madras, OR that has a lot of 60-66 Trucks above 1-1/2 tons.

I also know of a rancher that offered me a 1962 or 63 Chevy 2 ton for free with a rebuilt 2 spd rear axle in it. Body was shot and no bed but I had no where to put it at the time.

IT'S MINE

Just took delivery of the 1964 Chevy C60 mentioned above in my first post of this thread!!!

Now I can't wait for the weekend to start!!!

Look for a posting with my "soon to be created" restoration website in the near future!!!

Thanks and have a great evening!!!

Burgie

Kenny W,

Thanks for the tip on the used vehicles in your neck of the woods!!! I'll send you a PM this weekend...

Thanks again!!!

Update...

This weekend I did some more checking and here's what I found...

1. I took the truck for a ride. Again, when in Low, the truck shifted and drove fine ...yet when I shifted to High, it felt like the tranny was gonna drop out :mad: .

2. With truck running and stopped, I shifted from Low to High and observed a slight and momentary increase in engine RPM, then it went back to normal idle. Same thing happened when shifting from High to Low .

3. With the truck running, in neutral, rear axle in Low and e-brake applied, I crawled underneath and disconnected the Low side vacuum tube at the diaphragm. Yup, I got vacuum . High side line was dead (no vacuum). Also noted a corresponding slight increase in engine RPM with the line disconnected. Reconnected everything, went to the cab and shifted to High, and then disconnected the High side. Yup, I got vacuum . Low side was dead (no vacuum). Again noted a corresponding slight increase in engine RPM with the line disconnected.

At this point I felt confident that all vacuum lines/tubes were OK and that the switching mechanism was fine because I had vacuum and that vacuum did switch between the High and Low lines just prior to the diaphragm. I looked at the diaphragm and it looked suspicious. Perhaps it’s me but rather than a sealed assembly, it is an upper and lower housing with a rubber seal or gasket. Click here Diaphragm to see an image of the diaphragm. (Camera tilted to get best shot of unit). Perhaps it is OK? Don’t know yet… :confused:

No on to the real puzzling issue…when I shift into high (w/ normal connections everywhere), any problems and noises I hear are coming from directly beneath the cab…not the rear-end. While I am still trying to figure out the vacuum system and how everything is interconnected and dependent on each other, I gotta trust my ears . Sounds and feels like the clutch or perhaps a throw-out bearing? The grinding/clunking noises (like it’s jumping out of gear) are coming directly below me.

So, that’s what I have for the update. Next check is to do as Jolly mentioned, which is to remove the diaphragm and see if I can manually shift from Low to High. That will also give me an opportunity to more closely inspect the diaphragm assembly on the bench.

Thanks folks and please reply with any feedback or addition ideas/comments!!!

Take care and I’ll post again soon…

There is also a small shifter for your speedo cable mounted between the tranny and frame just underneath your cab. It may be what is causing the noises when shifting. Or it could be noise traveling up the driveshaft from the rear axle.

Try disconnecting the speedo cable from the tranny and see if the noise goes away when shifting from low to high maybe?

Burgie,

Lots of goods idea foregoing; I'd try the suggestion of disconnecting the vaccum servo and manually putting the axle in "high" and seeing how the truck drives, if for no other reason to see if the axle itself is ok.

Related story regarding noises vs. point of origin: about 15 years ago, I was working my way through college, and had a summer job as a laborer for a mason. I got to drive a '75 or '76 Chevy C-60 flat-bed w/ a four speed tranny & 2 speed rear. The axle was shifted by a knob and cable which came up through the floor bewteen the driver's door and the seat (possibly an aftermarket jury-rig); when changing axle speeds, if it didn't completely engage, there would be a horrific clashing/grinding noise from under the truck. It seemed like it was "under the cab", but that didn't make sense to me, as the gears that weren't meshing were way back in the diff (it was a 12' wb truck or longer). I finally figured out that the gear grinding was being "telegraphed" up through the drive shaft and through sloppy u-joints and splines, there was a lot of stuff along the way to make noise.
This truck was pretty beat though.

Hope your case is something simple ( and inexpensive !).

Good afternoon,

Well, I actually had some free time to do a little more investigation into this issue .

I took the diaphragm off and, with the truck running, had my wife switched from high to low and visa-versa a few times. With every shift, the actuator rod in the diaphragm assembly extended or retracted.

I then moved the lever manually and it appeared to move freely...though the "swing" of the lever was only about 1" or so...guess it doesn't take that much?

Anyhow, since tomorrow is a holiday, I'll have a free day to screw off and and do some more investigating. I'll take some more pics and let ya'll know what I find out.

For those interested, I scanned a cross section diagram of the Chevy 2 speed from my Shop Manual...

Thanks, in advance...

Whats the trick to getting the diaphragm off? I took the 3 bolts out and it slides of about an inch and won't come any farther.

Burgie,

Your picture links don't work...

Mike B

Mike, this is a 2003 thread. However, according to his profile he is still around. His links probably went away during one of the site updates.

LOL...I didn't see that ...good catch Martin!

Mike B

Mike, are you having the same problem? I can't get my vacuum diaphragm to come off the axle.

Good morning all.
This is my first post. I am in Maryland, where I understand Stovebolt originated.
I currently have a 1960 GMC 3500 Flatbed, and I just bought a 1964 Chevy 60 LCF (heavy duty), both of which I get to spend more time with this spring.
So, I just wanted to how or where I can see the photos of older posts, where the original link is broken.
I would also like to get in contact with "Burgie" to get information on the rear axle for the 64' C60.
TIA!

There is a splined drive plate in the ring gear carrier that is engaged by a sliding gear to select high range. That plate and gear are notorious for getting worn in such a way that the rear end will shift into high but as soon as a load is applied it disengages and goes in to a "false neutral". As soon as the driver backs off the power, it shifts back into high range. The only fix is to replace both items- - - -they wear pretty much equally. It isn't a terribly expensive fix, but it does require a full disassembly of the differential.
Jerry

Don’t know if these will help but here you go.
https://www.flickr.com/photos/advance-design_parts_co/albums/72157632724599711

Thanks guys.