The Stovebolt Site Forums The Parking Lot Big Bolts 1964 C60 Questions

Afternoon All,

I picked up a 1964 C60 last week (292 4+2) and have been working on it ever since. I am new to this era, and have spent a lot of time here reading and digging up info. But, I didnt find answers to all my questions and wanted to post them up here.

Last weekend I got the old 292 tuned up a bit and the 2 speed axle shifting properly again mostly. I can hi-low split shift up until 4th, and she doesn’t like/wont shift into 4 low. Just grinds away until brought to a stop. She split shifts all other gears perfectly though, BUT, the axle wont drop into gear without the clutch.

So; Clutch in -> Shift to first -> actuate 1st low -> clutch out -> reach speed -> actuate 1st high -> clutch in -> count 2, clutch out. Repeat through all other gears. Without the clutch, rear axle wont drop into gear. Its my understanding that hi-lo shift shouldn’t require clutch. I’m wondering if I’m not pulling strong enough vacuum in the line. Or maybe the axle diaphragm is worn? Or maybe im just overzelous on the gas. Also, I cant downshift trans to 1st at all. She just grinds horribly Wont allow 1st gear trans shift unless stationary or <4mph. I’m assume thats a synchro problem in the trans however.

I am currently tracing electrical problems. Ignition works fine, but nothing else electrical works. There is a secondary power switch next to the PTO controls. A translucent red light up 'pull out push in' switch. I cannot for the life of me determine what it is/does but it looks to be factory and wired from the factory, but it isnt shown in the witinf diagrams of the shop manual. Any idea? I can get a picture to help.

Other than the PTO control wires being fused and inoperable, the PTO and rams still work beautifully with the manual control on the frame. I didn’t expect a dual piston setup and was very happy when I saw that. Question though, the rams are very loose on the pivot points on either end. Like, hot dog down a hallway loose. Is there supposed to be a bushing between the ram and the shaft it pushes against?

Also out of curiosity, the GVW on the door states 19,500 lbs and research shows me that dry the girl should weight around 9500 lbs, so technically is this truck then a 5 ton? I was under the assumption that the C60 family was all 2.5 ton trucks, but this GVW shows me at double that, on a single dual axle as well.

I have to bleed the brakes once the new line is in, but have never bled brakes on a vehicle this old with hydro-vac and no ABS. I purchased the 1964 shop manual only to find that it is an augmentation to the ‘63 manual which covers brakes. The '63 manual is on order but still a week or so out, so what is the process to bleed the system on these older trucks? I have heard it different from everywhere I've researched.

The only other thing I know I have to do is wheels. All 6 are widow makers, and part of the reason I talked the price down so low. I don’t even plan on adding air to these beasts and am hesitant to even remove them from the axles. Rubber looks good enough, so ill drive on them until I source some proper ring split wheels to replace with. I figure when I park her this coming summer for a proper rebuild is when I’ll do the wheels as well.

My goal is to run her all winter logging season this year and then park her in the late spring for a month or two and do a complete overhaul. Pull the cab and get down to bare frame and clean, grind, and recoat every surface with POR15, redo the kingpins, replace wheel bearings and carrier bearing, replace a multitude of other parts, and fully rewire, re-brake, as well as repaint and possibly repower (discussion for another time).

There is very little info on any of this on the net, so from personal experience, does anyone have any suggestions? Again, I want to thank everyone so far for all that I’ve learned in the past two weeks here just reading. Old Iron is beautiful and just not that common anymore, so I’d love for her to continue running the roads for a long time, thus I don’t mind a bit of investment. She’ll make me plenty of money so im willing to put some into her. Plus, its fun, I like wrenching, and the wife actually likes this project because "that truck is beautiful."

Thanks all.

Not totally sure on this, but I'm not sure the transmission is synchronized in first gear. You probably do need to be almost stopped for that.

The red push-pull switch could be any number of things. Four way flashers comes to mind.

On your two speed axle, if you're running empty I wouldn't bother split shifting it. Just leave it in high. Loaded, you could either split shift it or else just run it through the gears in low, then put it into high after you're in fourth. This would depend on how heavy your load is and how the truck handles it. You'll get the feel for it after you've driven it some.

I'm sure others with more knowledge than I will be along to answer your other questions.

as far as shifting the 2-speed rear, I am not an expert (there are guys on here that have been driving them way longer than I but, using your terminology, if you are in low, you activate high, then let off the gas a bit to allow it to shift into high. if shifting from hi to low, activate low, let off the gas a tad, then give it more gas.

I have a viking 60 (1958) and the tag on it says 16,000 pounds. Yours probably has a bit heavier axles and springs to make up the difference. Mine has a steel dump on it and also weighs about 9 empty. I don't shift the rear unless I am real loaded (pulling my 7,000 pound travel trailer) and even then, only if I am going up a hill and need to find the right gear.

As far as bleeding brakes, I made a power bleeder out of a cheap garden sprayer and an extra master cyl cap. Bleeding sequence should be pretty much the same as on my 58 with the hydra-vac. Hydravac unit has 2 bleeders on it, bleed the one farthest away from the output line first, then the one closest to the output line next. The link below is the sequence for the 55, which has the hydrovac unit on passenger side. My 58 is on driver side so, I swapped the order of rear wheels (per instructions in my 58 manual). Pay attention to the loosening of the upper shoes before bleeding! (if you have the same brake shoe setup) otherwise you won't get all the air out.

http://chevy.oldcarmanualproject.com/shop/1955truck2/55ctsm0507.htm

As far as your transmission, it is probably an SM420, and 1st is not synchronized so YES, it will gtind when going into 1st unless you are barely moving or double-clutch it.

The 2 soeed is a bit of an art takes a bit to find the groove of when to shift . It's always helped me to listen to the truck when shifting . Use the 2 speed button early like when your going from 2 high to 3 low , hit the button to low range then shift up to 3rd. 3low to high pull button up ease off or maybe touch the clutch to let everything get meshed. More you drive it you will get the feel for it and I'm with 69 cuda I only use the low side loaded for rhe most part on my 58 also.

If you dont have a bleeder trying to get going on an old system like that crack all 4 wheel bleeders top off the master let it sit and let gravity do the work for you check the master here and there topping it off let it sit like that all day or over night . Close it back off then strat bleeding it regularly. Will get you close rather then pumping it half the day.

I'll leave the rest of it for the experts, but just a quick note on this part:
It's common in the truck world to confuse "GVW" with "2-ton" versus "1/2-ton," etc). First off, go read our Tech Tip on this subject. But in a nut shell, the truck's GVW as listed on the data plate is the important one to know for loading the bed of the truck. Whether the truck is called a "half-Ton" or a "2-ton" or a "5-ton" is an archaic holdover from the early days and *only* refers to the weight/load rating of the *front* axle.

This becomes important when you start thinking about a repower. If you go with a heavy engine (like a V-8 or a diesel of some sort) and a heavier transmission, or anything that puts more weight on the front axle (including the rest of the front of the truck) than, say, "2 tons," you will want to replace your front axle, as well, or you may be dangerously overloading your front axle.

About the 2-speed -- Smooth 2-speed axle shifting comes with practice. And don't use the clutch! Do it in this order -- 1. Pull (or push) the knob in 2. let off on the accelerator and count to two/wait for the clunk, and 3. return to the accelerator. (Don't get steps one and two reversed or you will get a bad noise ) That's how it always worked for me on my '65 big truck. Upshifting is easier than down shifting. And keep in mind that shifting the 2-speed is much harder when the truck is empty/light. Try leaving the axle in low range until you get to the top and then shift the axle into high -- treat it like an overdrive. When it comes time to down shift, leave it in high until you get to the bottom (when you are stopped at the light, push in the knob and wait for the clunk). The purpose of the two-speed is to help the "little" engines start big loads and to keep speed up when shifting on hills. So when the truck is light/empty, you might not need to use low range at all. Of course, your application may be different from mine -- I had a GMC 4400 with the 305 v-6 (the torque monster). The 292 may be similar, though, so try it and see. When it comes time to drive the truck with an actual load on it, then you will want to use the 2-speed on every shift and you will find it behaves much better.

Now get rid of those RH-5's as soon as you can. Do *not* load that truck with much weight until you have safe wheels, and new, properly inflated tires! (and good brakes and steering, too!) We want you around for a long time now that you've found us.

Welcome aboard! Check out the rest of our Tech Tips, too.

John

Welcome to the Stove bolt

I agree with all of the above information.

As for you wheels, how many lugs do you have? If 6 -lug, they will be Budd wheels and you should be able to get replacement 22.5" tubeless wheels and tires. They came on lots of trucks and buses in the 60's and 70's. The RH-5's have been known to blow apart without warning, so take John's advise and replace them before putting the truck back in service. When you are ready to replace them, just let the air out and then they are safe to work around.

Mike B

Good to know about the transmission in 1st gear. I never knew they prevented 1st in the downshift. I assume this was to protect 1st since its so crucial in getting moving with a load?

I was of the understanding that shifting the axle shouldn't require the clutch. I assume I was just overzealous and didn't give it the time to engage before getting back on the gas. Ill play with it some more once I get the brake line in. That said, is it bad to use the clutch when shifting hi-lo? Also, I assume that to use axle low when downshifting and engine braking is just a reverse of the up shifting process. Any special considerations when downshifting through each gear? Seems complex and possibly damaging if not done perfectly.

Yeah the wheels are a large concern on my end. They are actually the 10 lug style on a 5 bolt front axle so replacement should be plentiful at the local truck yards. Ill start calling around tomorrow for a set in decent shape. I do a lot of "questionable" and borderline sketchy things on farm life, but center splits flat out terrify me and I give them wide berth. Surprisingly not illegal in this state, but not any reason to try and keep them. Any firsthand advice on style of tire? Research shows that tubeless radials seem to handle/ride better, and I'm all about that!

I appreciate the insight on the terminology, and it all makes sense. I'm from the world of M35A2 Deuce-and-a-Halfs and M813 5 ton and the terminology was confusing me. But good call on the front axle designation in conjunction with a repower. The goal would be to repower with a diesel so ill have to look into front axle weight to see what is possible or what may need swapped.

Does anyone by chance have any advice on literature for this series truck? I'd love to find all I can to learn everything about the line to know what options there are out there. Barring shop manuals, I havent really found any good spec sheets.

And Great point on the bleeding process with gravity. I like that idea a lot! Im going to give it a shot if I can.

Thanks for all the replies and input, I greatly appreciate it all.

The 22.5" one piece rims with the 5/10 lug and the 5.25" center hole are getting hard to find. That lug pattern is available in the 19.5" rims, but they will look small in your wheel openings.

The 22.5 tubeless rim is the direct replacement for the 20" tube type rim. To keep the same tire diameter you go UP one tire size number when going from 20 to 22.5.

7.50x20 = 8.25x22.5
8.25x20 = 9.00x22.5
9.00x20 = 10.00x22.5
10.00x20 = 11.00x22.5


Mike B

"That said, is it bad to use the clutch when shifting hi-lo? Also, I assume that to use axle low when downshifting and engine braking is just a reverse of the up shifting process. Any special considerations when downshifting through each gear? Seems complex and possibly damaging if not done perfectly"

Shouldn't really need the clutch , I always just pop the button down to low then give it an easy rev on the motor. Listen and feel when it shifts range you will get more use to hearing the right rpm for the shifts. 4 low to 3 high pull up to high then shift to 3rd and so on going down or up. If you are using the 2 spd the 2 speed button first then shift . Little practice you will get it figured out..

As far as literature is concerned, I would check Ebay. You never know what will pop up there.

Don't use the clutch when shifting hi/lo, but must be going slow enough and speed up engine to be pulling to engage, otherwise if engine isn't going fast enough for the lower gear, it won't engage and just ratchet.

Ed

Appreciate the info Mike. From what I have determined via research and comparison with other pictures is that I have 10 lug 8.75" bolt circle wheels that are hub piloted. Not sure on center bore yet, likely need to get back to the shop at the other farm and physically measure them. My guess is that its either the 5.25 or 6 inch center bore. I assume that rear wheels should be the same as fronts for the trucks? As in they wouldn't have made different lug bolt pattern/center bore/lug piloted on the rear axle from the front axle on the same truck? I don't care about single piece wheels, im fine with 2/3 piece lock ring style so long as they are rated for my loads.

I don't know of any 20" rims with the 5/10 lug and 8.75" bolt pattern that aren't the RH-5's...

You need to be under load (going up hill) to be able to down shift from hi range to low range. You can't practice on flat ground, it will grind. As others have said, start in 2nd low rear and stay there until your in 4th gear and then switch it into hi rear. The only time I don't do it this way is if I have a heavy loaded.

Mike B

I seriously appreciate all the advice. Thank you all. I think I have the axle down, and am currently looking for wheels.

After another late night work session all my lights finally work. It was mostly all original, but had "new" wires spliced in and run every which way. It was a nightmare but thank goodness for my shop manual with wiring diagrams.

I discovered the original primary power wire thru the fire wall was unfused. At one point it shorted and melted and how there wasn't a fire is beyond me. It roasted electrical though. The previous owners band-aid fixed it and ran it with no electrical beyond the ignition. Needless to say, everything is functioning proper now with a fuse before the firewall. Was it normal to not fuse the main wire thru the firewall back in the day? If so, man we have come a long way.

https://imgur.com/a/jZSWCjS
https://imgur.com/a/e4hpEjW

I had to cut out every connector from the firewall forward barring headlights. Any advice on where to locate new connectors of the same style? It appears that the original generator is long gone and in its a place is a standard 1 wire alternator. With this setup, I assume the original voltage regulator needed at all anymore?

Still working on brake lines. Inevitably with each new piece I add, another old piece breaks. Coupled with odd ball thread sizes and pitch and its been slow going. Next round of parts on Tuesday, ill give her another shot on Thursday. All the steel for the bed is ordered and I should be fabricating next weekend (fingers crossed).

I finally got to the gas tank, and boy is that sucker small. Something like 15 gal? I cant imagine a very big range on that puppy once loaded. Is it advisable to run a secondary, or just all new and larger fuel tank, nested in the frame? Driving with my back resting on the gas tank seems....well yeah. That and I can smell gas anytime im near the tank filler neck. Are these old gas caps supposed to vent and allow pressure bleed-off (thus, smell) or should it seal proper?

My 1963 shop manual shows no fuse protection to the ignition switch so I am gonna say that if there was any in 1964 it was the first year. My 1969 manual shows the fuse link between the battery and the terminal block, leaving the big cable to the starter as the only one unfused. I believe the terminal block on the C series was mounted high on the firewall, my T50 was near the battery, down low near the front bumper. Since the fire engine wiring was much modified by the body builder, I replaced the terminal block and moved it to the radiator support for access and protection.

The original voltage regulator should not be needed except for the wiring to the idiot light on the dash. I gutted my regulator and jumpered the connections from the alternator to the light so it still works and the "regulator" looks stock. I used a 3 wire alternator to preserve the dash light and get better regulation as mine is a fire truck with heavy electrical loads and now has a 105 amp alternator. I will install a voltmeter in the spot where the added gas gage is once I reconnect the stock gage. The fire truck builder wanted to use a standard sender which has now become unreliable and is obsolete. I have a currently standard sender to make the original gage (which is still in the dash) work as the factory intended.

I do not like the long, usually unfused, wires that are needed to install an ammeter in the dash, the voltmeter tells me more anyway.

Your truck looks great!

Going against the grain here on some of the replies, I always use the Clutch when shifting a 2-Speed Rear. Not only is it recommended by the factory, it will shift smoother with using the Clutch. And I drove trucks with 2-Speed Rears for over 23 years, lol. But all of mine were Electric Shifts.

HF Farms, I read your first post on your shifting procedure and everything sounded fine to me. Although I have no experience with Vacuum, in my opinion it sounds like you losing something and not getting full Vacuum to the Rear.

Just to add a little extra, when Split Shifting Hi to Lo, shift the trans first, then hit the button down just before letting the Clutch back out.

Right on the Transmission, 4-Speeds, back then anyway, are not Synchronized 1st.

My 1957 Owners Manual says to "release the accelerator" to shift...nothing about using the clutch...did that change in the 60's?

I've been driving electric and vacuum shift for 20 years and I never use the clutch...

Mike B

The '62 GMC 6500 that I used to drive starting back in '71, had the 2-Speed Shifting Instructions as well as the Shifting Sequence attached to the Visor by the Factory, which stated to always use the Clutch. Since that truck, I drove many more that also had the same type instructions. I learned that way and never changed. Not sure about anything in the 50's. I never drove anything that old with a 2-Speed, lol.

I know it's possible to shift one without the Clutch and I sure have, but always like how it shifted by using the Clutch, especially in the lower gears. I also believe that it is not as hard on the drivetrain as well.

Your 100% Correct Bill

While I've done it both ways, it's always smoother with the clutch.

The whole key is matching anticipated RPM with Road speed, and Practice.

Tom Petroff

See, and that's what I was wondering. The "official" Eaton instructional video doesn't indicate the need for clutch nor does the shift pattern up by the visor in the truck, BUT I know a number of farmers in the area that say to always clutched it since its easier on the rear and can prevent damage and wear. Really, I guess its six of one half dozen of another? Operator choice I guess? The shift pattern seemed to drop in easier with the clutch though vice release of the accelerator. But, in reality, I know nothing and need to get her back on the road and play around a bit more with it all.

The one warning I continually see is that the axle must be in high prior to any shift of the transmission. But, I know of trucks and others in the thread above who advise to just run through all the gears in low and then pop into high once up in fourth. I definitely "accidentally" shifted the trans while in lo once while on the road last week, but saw no ill effects. It seems like each model year of style truck of the era had different shifting patterns though. Heck, ever drive a deuce-and-a-half? The shift pattern on that is just weird compared to everything else.

I do need to check vacuum lines from the hydro-vac forward though to ensure I am pulling good vacuum. Maybe that's the cause of the hesitation to shift the axle.



Good to know. Amazing what times does to designs and standards. I cant imagine running un-fused wires these days. Than again trucks these days have a lot more flammable capability than trucks of old. Not much on a 64 to catch fire a burn.

And thanks! I lucked into the body which is in great shape, and Im happy that I can focus more on drive train and such to make her a workhorse.

Alright, stupid question time!

I found the original "protection plan" book and in it are the numbers for the trans, engine, axle, etc. How can I identify what these are in modern english?

For instance, axle no. is P61011. What does this translate into? I am trying to determine axle ratios at the moment and figured this would contain it. Internet research shows nothing thus far.

You can go to GM Heritagecenter.com
under archives drop down menu
Look up your year and model and download RPO codes brochures, manuals


https://www.gmheritagecenter.com/

See if that will help.
Lot of archived info there

Tom