The Stovebolt Site Forums The Parking Lot Big Bolts NOOB Needs a Hand With a 6400

Greetings, all. I bought a '57 Chevrolet 6400 grain truck at the beginning of the year and I've been working on beating it back into some sort of safe, reliable, useful condition. The truck runs OK, but the brakes were shot and the maintenance schedule has been ignored for, um, probably decades. Until now, most of the work I've needed to do has been pretty much self explanatory, but I'm to the point now where I could use a little advice with some of the finer points. I recently stumbled across these forums and am very glad I did. Maybe you guys can give me a hand so I can get this 'ole dude back on the road.

Brakes: They were totally hosed. Leaking from all the cylinders and the master, booster, and lines were shot. Master and booster are rebuilt, all steel and rubber lines replaced, front cyls. rebuilt and shoes relined. Now I'm working on the rear. This setup has two wheel cyls. and two adjusters per side.

Two questions: There is some minor corrosion inside the cylinders. No massive pits, but there are some small ones visible. I've honed the snot out of them, but I'll never get it all out. I've already tied up a bundle in this brake job and can't really afford $80 a piece for four new cyls. When rebuilding wheel cyls., is there any percentage of bore damage that is acceptable? I've never rebuilt them before and don't know what I can get away with. I'm trying to walk that fine line between doing enough to get it functional and safe without spending stupid money to get it there. I could live with them weeping a bit over time, but I don't want any gushers. Also, what is the correct adjustment procedure with two adjusters?

Rear axle: This is a two-speed rearend with full floating axles. The rear wheel seals have been leaking and I'm replacing them. I didn't have any trouble getting it apart, but I'm not exactly sure what the procedure is for adjusting the bearings when I reassemble. It has an adjusting nut, a lock ring, and a lock nut. Is it similar to the front? It looks like the outer bearing has spun on the spindle at some point. Was this from misadjustment and is it fatal to either part? No grooving or detectable wear - just a little polished. Not severe damage, but I want to make sure it doesn't continue and get worse!

Also, the gear oil in the rear axle looks like it has been there since '57. Ick. How can I drain it? I don't see a drain plug. Will it drain if I pull out the bottom differential carrier bolt or is there another method?

Lastly, where the heck can I get a shop manual for this thing?!?

Sorry about the length of my post, but I wanted to give as much info as I could. Any and all help and advice is much appreciated!

Hy 1herrick1, Firstly welcome, now to your questions the pits/holes in your wheel cylinder bores will accelerate the wear on your new wheel cylinder cups, if the cups must travel over them, if there in the center it's not a problem, cylinders can be rebuilt by boring oversize and sleeving with stainless steel, rather than buying new ones, so what price safety. You can drain the diff. oil by removing a few bolts from the bottom of the cover on the back side of the diff. Many suppliers have manuals for sale, rather than try and detail the rear wheel bearing adjustment here I would say purchase a manual and follow the procedure detailed in it, try American Classic Truck parts for the manual [they sponsor this sight], hope that helps.

About the brakes.
Don't take any shortcuts. Your "what I can get away with" mentality should not be applied to brakes for the sake of safety.
If you have spent money on new shoes/linings then you don't want any pits at all in the cylinders, as any leak and the shoes are no good. If it was used around the farm, and still had the old, probably wet, shoes then some very minor pits may be OK if you check the fluid level in the master very regularly.

Personally I would either have your old cylinders stainless steel sleeved and pretty much forget about them forever, or buy new cylinders. If you have them sleeved then I like the work that "Mark the Machinist" does, search the forum for more info on him, and his contact info.

Unless your service manual (available from most all the restoration parts places) says otherwise I would adjust the rear wheel bearings as you do the fronts.
If the spindle is not damaged, and the bearings are still good then probably nothing more needs to be done.

Grigg

I found the manual for my '56 beast on Ebay, look around on there from time to time and you'll find one I'm sure. All of the questions you have asked are in the books and it is really better to follow proceedures for your specific year & model.
The axle you have may be listed in this 1956 GMC 100-500 series truck manual, the brakes should be pretty much the same, the adjustment proccedures are in there.

The rear end oil sounds like what was in mine, looked an awfull lot like moldy hersheys syrup with some spoiled milk in it, smelled as bad too. If you take a wire brush to the bottom of the pumkin there should be a drain plug under there, but if not I'd reccomend taking the cover off and having a good look around the rear end anyway. I found a load of pitting on the teeth of my ring gear and some of the PO's Mickey Mouse engineering that needed some attention. it's also a good way to get any residual gunk out of the rear.

edit-
In reply to a post with some good questions that now seems to have disapeered.... it read:
"what's the cost difference between the labor to pull, have the sleeve work done and reinstall, down time, bleed
vs.
just buying - new wheel cylinders? down time is your time and cost. certainly new ones will last another dozen years...plus
or maybe I'm missing something here??"

And my answer,
Depending on the cost of new wheel cylinders having the old ones sleeved can be cheaper. It is longer lasting for sure.

Your/the mechanics labor to replace or have sleeved and reuse is the same.

If you plan to keep the truck long enough for a second brake job down the road the stainless sleeves should pay for themselves in saved cost at that time (no new wheel cylinders to buy) if they need kits you can often install them on the truck, no need to remove the cylinders, Just clean in place, so saved time too.

I was so excited to see a question I could actually answer, only to see that it was already answered!

I also used ebay to get my service and owners manuals...although reading into the service manual I realized that 1. I don't even own one tenth of the tools required and 2. I don't understand the english they speak in.

Maybe some day....

You will have a differential fill hole on the back cover. Make sure that you can take the plug out of the fill hole, and refill the axle, before you drain it.

Take the bottom bolt out of the "pumpkin" where it connects to the axle to drain the "goop" out of the axle.

If it's really goopy it may not come out the bolt hole.
I vote for removing the cover, flushing, and inspecting before resealing the cover and refilling. Even if it does have a drain on the bottom, I would still want to take a look inside.

Grigg

My experience with new wheel cylinders has been disappointing. I would recommend having the old ones sleeved, regardless of the cost.

You will need a manual to bleed those brakes because they are different. All your adjustment question should be answered by a shop manual.

Thanks for the replies. They are much appreciated. I've got a manual ordered.

As far as the wheel cylinders go, well, I don't have a choice right now. Legitimately, they probably should be replaced or sleeved. I had the master cylinder sleeved when I rebuilt it because it was in really rough shape. I checked with the outfit that did the master for me and it would cost as much to get the wheel cylinders sleeved as it would for new ones. Either way, it would cost well over $300 to do all the rear cylinders. I've got $600 in parts tied up in this stupid brake job already and I've still got to go pick up $60 worth of rear wheel seals today. The kids come before this old truck. I'm not dumping another $300 in it two weeks before Christmas, but I've got to get it back together and out of the middle of the barn. I'm just going to rebuild them as-is for now. They were losing a little fluid past the piston into the boots before I tore it down, but none of them were puking into the rest of the brakes. They've GOT to be better now after having all the gook and corrosion cleaned out and getting honed and resealed. The bores don't look great, but they are 100% better than what they were. I'll go back in one wheel at a time and replace them this summer. It's not going to stray far from the farm before them anyway. The crusty steel lines, ratty hoses, worn out master, and leaky HydroVac are all replaced or rebuilt, so at least I can count on it generating and holding pressure. It should stop now.

I'm going to get the rear hubs and bearings cleaned up and back on with the new seals this weekend. I'm going to go ahead and adjust them just like I did the fronts. It the manual says different when it shows up, I can readjust them without tearing it all back apart. There definitely isn't a drain plug on the axle. I'll go ahead and try pulling a couple bolts out of the bottom of the carrier to drain it. The oil isn't like molasses. It's just old and dark. If I can find a way to let it out, it'll drain. There's no "cover" on this axle and tain't no way I'm tearing the carrier out of it to do an oil change right now. Too cold to start any more major surgery!

Three bolts on the bottom of the differential will do the drain job. I think I can get some new cly for the rear OES 35.00 each You may need the adjuster pinnions also I think I can still get those too.
I have a 1946 Chevrolet 2T that looks better that the day it rolledout of show room. As for other information you may need drop me a note and I can copy any service information you may need. I am an retired Chev dealer. During the 40's and 50's worked in Service Alwayys willing to help. Going sout for the winter so can't help much after Jan 1st

On the rear adjusters, if you haven't already, remove them and clean the gunk out of the threads. I had a horrible time trying to adjust a couple of them because they were gummed up pretty bad. Makes a lot of difference!

I might be a lil wierd, but when I was adjusting the shoes out, I would slowly rotate the drum till it had a firm drag, then I'd rap the drum with a big rubber mallet about where the adjuster screw was while turning the drum. It will loosen up a couple times and need to be adjusted again before it stays firm, then I backed it off a bit and moved to the next shoe.
Just allows the shoes to center themselves properly as I turned out the adusters, minimizes how much you need to adjust them after you've driven it and tested the brakes a time or two to center the shoes properly. Since the shoes aren't connected together on the rear you can effectively do one shoe at a time.
Just what I did anyway,...

Don't be shocked if your wheel cylinders leak worse after honing and putting new kits in them after you get them back together. I've tried to cut corners on wheel cylinders in the past and found once you get the yuck and grime out and hone them that they are worse than they were.

Well, you'll all be happy to know that I changed my mind. The last two wheel cylinders were making me nervous. They were really pitted. 10 times worst than the rest. In between work and dinking with this truck, I've been cleaning out the shop and got a ridiculous amount of money on eBay for a couple items that I almost threw in the scrap tub. I figured that I might as well reinvest my little windfall in some peace of mind. I pulled the other two cyls. off the rear, packed all 4 of them up, and sent them off to CA to get sleeved. Better now before I've used and ruined the new kits than have to do it all over again this summer when I'd rather be using it than wrenching on it. His prices were going to go up at the first of the year anyway. Best of all, now I won't have to think about it anymore. I'll let y'all know how it comes out. Thanks again for the advice and answers!

Good choice.
Stainless sleeves right?

Grigg