1969 gmc

[jnavar]

Just purchased this truck
This is my first vehicle with drum brakes all around. Is it normal for it to take 4-5 car lengths to slow down? I am also a shorter guy so would like to know if its possible to make the clutch a shorter distance (instead if having to press it down to the floor board) to fully disengage the clutch?

[special-K]

Welcome to the board! Nice looking GMC. Is it an 8-lug 4wd (K2500)? It's hard to reply to what you are describing, but you will definitely notice the brakes don't grab like disc brakes. What do you mean by slow down? Slow down at all or slow down significantly? I've always driven these trucks, both drum and disc, and used to not even notice a difference. I'm sure there is a decent difference, but I never paid much attention to it. I haven't had one with drum brakes for a very long time. I guess it matters all the more these days with other vehicles able to stop much shorter than years past, as well as the knucklehead way people drive ahead of their thoughts these days. You really need to be on your toes.

[jmlloar]

The only difference I could ever tell was between power and manual. And even with disk the manual brakes sucked.

[Ol' Drippy]

Having all four drums properly adjusted is really important. You want it so that they drag just a little when the wheels are turning.

[Caddylackn]

All 4 drum brakes should have close to the same stopping distance as disc/drums. The big difference between disc and drums is the amount of pedal force required and an increased stopping distance when the drums are wet or very hot (long steep grades). If everything is working correctly, you should not see a decrease in stopping ability in normal conditions.

What commonly happens is old cars that have been sitting awhile with moisture in the brake fluid and both pistons of each wheel cylinder are not moving (one gets frozen) so only one brake shoe is moving and not both. Pretty soon the one shoe starts to wear very quickly and there isn't enough travel left in the linkage to take up for the worn brake shoe. Or the drums have been turned too many times and there isn't enough travel in the brake linkage to engage the drums when the shoes are half worn.

[jnavar]

Originally Posted by special-K

Welcome to the board! Nice looking GMC. Is it an 8-lug 4wd (K2500)?.... I guess it matters all the more these days with other vehicles able to stop much shorter than years past, as well as the knucklehead way people drive ahead of their thoughts these days. You really need to be on your toes.

Yes she is an 8 lug 4x4... So far I am pretty happy with her, but people out here seem to drive as if someone is chasing them, thus brakes are a high priority. When pressing the brakes it takes about 4-5 car lengths to slow down.. If someone jumps in front of me atm I would more than likely not be able to stop.. The PO(my uncle) assumed it was normal behavior, but it doesn't seem quite right to me..

Originally Posted by Caddylackn

All 4 drum brakes should have close to the same stopping distance as disc/drums. The big difference between disc and drums is the amount of pedal force required and an increased stopping distance when the drums are wet or very hot (long steep grades). If everything is working correctly, you should not see a decrease in stopping ability in normal conditions.

What commonly happens is old cars that have been sitting awhile with moisture in the brake fluid and both pistons of each wheel cylinder are not moving (one gets frozen) so only one brake shoe is moving and not both. Pretty soon the one shoe starts to wear very quickly and there isn't enough travel left in the linkage to take up for the worn brake shoe. Or the drums have been turned too many times and there isn't enough travel in the brake linkage to engage the drums when the shoes are half worn.

Thank you for this.. It does seem as if pistons are frozen.. Is there a way to unfreeze them or am I better off purchasing new ones?

[jmlloar]

new wheel cyl and hardware kits are reasonable.
If I don't know when they were last serviced I just replace it all. Shoes can actually harden up and be less effective.

Don't scrimp on safety. Its to late after an accident to say "maybe I should have repaced that".

[HO455]

I would pull each drum off and inspect the brakes. You may have more than one issue.

Look for anything broken or bent, uneven wear on the shoes, oil on the shoes, glazed drums, grooved drums, drums that are exceeded the stated wear diameter or rusted drums. You should be able to move the slave cylinder pistons into the cylinder slightly by prying with a screwdriver to check for a frozen piston.

It may be that new shoes and having the drums turned followed by a proper bedding in of the new shoes may solve your issue.

[special-K]

When I rebuilt the '70 C/30 I used for my business I never considered converting to discs like you see people do today. I located all new parts and rebuilt the whole system. This was a 157" wheelbase truck with an 11' service body with 15' ladder racks, always loaded up, too. That thing stopped just fine. I went all out because I was building a daily work truck rather than buy new. You could get the same results without going to that extent. Drum brakes are very serviceable.

[jnavar]

Thank you to everyone! I ordered all new wheel cylinders and brake pads..hopefully I can get those in working order soon... Also has anyone seen this before? It isn't a twin stick since the lever to the left of the gears is not attached to the transfer case.. The lever is attached to something in front of the sm465..

[Steeveedee]

Need pics, but maybe a PTO lever?