1976 C10 - Trouble moving - Automatic transmission

[kcackler]

I have a 76 C10 that has been sitting for about 8 months due to being busy with life. Now that it's nice again, I'd like to start driving it some more, but I can't get it to move. I can start it and put it into gear no problem, but when I put on the gas, all it does is rev up. Once I get it to maybe 4-5K RPMs (No tachometer, just guessing), one of the rear wheels finally starts to spin, but the other one remains stuck and I go nowhere. I put it into neutral and was able to pull it into a new parking spot and both wheels turned while pulling.
I'm not sure where to begin troubleshooting.

Any advice would be appreciated. This is a project truck and it's entirely likely that something is seized, but with both wheels turning when I towed it, that seems less likely.

When it was parked, it drove beautifully. We're moving in a month, and I'd really like to drive it to the new place rather than tow it.

I'd like to start troubleshooting this weekend, so any tips / troubleshooting steps would be appreciated.

[mrolds88]

Check your trans fluid, sounds like it is low.

[kcackler]

Will do. Have to pull it up the hill to more level ground first though. Will report back.

Thanks

[kcackler]

Towed the truck up to level ground yesterday and started it up. Let it get warmed up and checked the fluid and it looked fine. Jumped in and put it into drive and it kicked into gear and moved. Was able to drive it around the block no problem, but it felt really stiff. So I went out today and started playing with it and it feels like a brake is seized on somewhere. I have to really punch it to get it to move and I can't get it to coast at all unless going downhill. On level ground, when I let off the gas, it stops moving pretty quickly. If I put it into park and pump the brakes a few times and then put it back into gear, it takes a little more effort to get it to move. When I put it into gear and let it idle, it groans a lot like it's trying to move but can't.

Any ideas? I don't want to drive it until I know it's running properly again. We'll be moving in a couple of months so I need to fast track the fix. I'm thinking maybe we need to disassemble both brakes, clean them up, and put them back together, but I want to make sure that's a logical next step before doing that.

[69chevytrucker]

sounds like brake hanging up if park brake was on for 8 months i would start there and see if it released maybe jack up rear and see if wheels move freely

[kcackler]

Parking brake shouldn't have been set at all but I just tried to push the pedal and it won't budge. Might need to just redo the rear brakes entirely.

I'll jack up the rear and see if the wheels will turn.

[kcackler]

Reporting back in. Jacked up the truck today and the right rear wheel was completely stuck. Left rear spun freely. I took the drum off and cleaned and lubed all the bits, put it back together and it drove fine but once I hit the brakes I was stuck again.

So what would cause this one brake to lock up? I'm thinking maybe wheel cylinder? Any other ideas?

[69chevytrucker]

sound like wheel cyl to me too

[kcackler]

OK - Mostly rebuilt the bad wheel and it's got the same symptoms as before. Can move it as long as the brakes aren't pumped to the floor. As soon as they are, it seizes up there and you can't move the truck. I put in a new wheel cylinder and new springs for all of the parts and also greased everything up. Put it back together and the drum spun freely. Hopped in, moved it. Hit the brakes hard, and now I'm stuck again.

Any other ideas?

[InitialBoss]

How is the brake fluid in the reservoir? How are brake lines to it. I'm assuming they aren't leaking near the wheel because you would see that but what about the whole line? Maybe an issue with the line as the brakes work after you rebuilt them. I'm just throwing out ideas. I'm not experienced with cars and trucks and am just speculating. I want to know what the resolution may be as well so I can learn from this too. Poor vacuum with brake booster or MC maybe? Again just throwing out ideas. I had to get my MC and brake booster replaced since the fluid rusted them out in my 78 C10. Of course my truck was sitting there for about 3 years with out it being driven.

[buddy_1]

Sounds like a collapsed line or hose. Jack up the rear and pump the pedal until the wheel locks up. Open the bleeder screw and see if the wheel frees up. If fluid comes out and it doesn't free up, you have a brake cable or mechanical spring or pivot problem. If it does free up you have a restriction in a line or hose. To figure out which line is the culprit tighten the bleeder, pump the pedal until it locks up again and loosen the line going into the wheel cylinder. See if it frees up. If it does the cylinder is good. Repeat process and loosen line at the T-block in the center of the differential. If it does the line is good. Repeat process and loosen the line going to the flexible hose for the T-block. Which ever fitting doesn't release tire would be the one to inspect more closely or replace.

[kcackler]

Thanks for the troubleshooting help. I just went out to do that and I couldn't get the back brake to seize up at all, no matter what I tried. I thought that was a little weird so I jacked up the front and sure enough, both front tires are seized up too. I definitely fixed the rear tire with the new wheel cylinder and parts, but now something is freezing the fronts.

I bled both the fronts and they spun freely immediately, so it's going to be the line, right? Is it possible it could be the master cylinder? It's definitely an older cylinder and I have a replacement, but I don't want to go to the trouble unless I have to. Whatever it is, it's affecting both front wheels so it's probably a main line, not one of the branches.

[buddy_1]

Did both sides free up by opening one bleeder? Or, did each one free up when you opened its individual bleeder? Yes it is possible to be a master cylinder problem. Pump the brake until the tires lock up then loosen the line at the master cylinder to see if they free up. These old trucks are notorious for hose concerns. Pump the brake until the tires lock up then loosen the line fitting going to the frame end of the caliper hose. See if it frees up, if not, the hose is collapsed internally.

[kcackler]

Each side freed up when its individual bleeder was cracked. I had to go double check this just now because I wasn't sure, but the I definitely had to bleed the drivers side to make the drivers side wheel spin and the same for passenger side.

I'm going to go test the other theories now.

[buddy_1]

Check those caliper hoses.

[kcackler]

That's what I'm working on now. I figure it's got to be that at this point.

Any tips on getting these *@(*#$ hoses off? I can't get a wrench inside the rail for the small nut on the inside and the big nut on the outside is rust-welded on. I just sprayed it down. Will try again in a few minutes.

[kcackler]

Just figured out that you don't turn the caliper side of the hose. You have to disconnect the hard line then pop it off. Guess I'll keep working at it.

[kcackler]

An hour in and not much luck. Mosquitoes started getting to me so I'll try again tomorrow.

I got the c washer off of the caliper side of the hose and was able to then slide it in toward the engine bay so I could get my line wrench on it, but that didn't work at all. Tomorrow I'm going to have to try again but with vise grips since the wrench wasn't working.

[bnoon]

I recently had the same issue. In the end it was easier and cheaper to replace the whole line from front to rear. Luckily I had another truck with a good hard line from the front to the rear section, then I snapped off the hard line at the rear T fitting and used a 6 point socket to remove the old fitting. Pulled out the good ol double flare tool and remade that connection (since the fitting on the other truck was rust frozen too). I had to remake the passenger's rear end housing line too (new line for about 6 bucks from auto parts store), then wheel cylinder on that side as well (about 8 bucks). Took about an hour to plumb the whole thing vs what I'm sure would be several hours trying to get old ones off. Good luck man!

[buddy_1]

You have any luck with those fittings?

[kcackler]

Not yet. Had to take a break to get some stuff done around the house. New brake lines should be in tomorrow and I'll take another crack at it.

[kcackler]

Still no luck. Does anyone know what size these fittings are? I can't get a 3/8 line wrench over them but 7/16 feels sloppy.

I'm about to step up to vise grips but I doubt I'll have much luck. I'd really like to avoid running new line just because I don't have a donor available and I'd be doing it from scratch...

[buddy_1]

Try a 10 mm

[donthekawguy]

Be careful with the large sheet metal looking nut that holds the line to the frame. I have been looking for new ones for the last week and can't seem to find anyone who makes or sells them. To get the fittings lose you could try some needle nose vice grips and heat from a torch right one the connection. Don't get it too hot but it will break loose.

[cadillac_al]

I have a set of flaring wrenches that I call nut rounders. They are only made for installing line fittings, not removal. I have always had to resort to vicegrips to remove rusted on brake fittings. Good luck.