K3500 with nv4500 bucking when going into 1st gear

[GreenMonkey]

Probably the wrecking yard is your best bet on backing plates. One of the bad things about owning and repairing the big trucks (8 lug 2500/3500s) is there weren't as many of them made as the half tons, so parts are more scarce to begin with. Then factor in that these were, and still are, work trucks and so got the snot run out of them on a regular basis. So a lot of the parts we now need are worn out, or close to it, and the supply of replacement parts has been depleted too....
My one ton is in very good shape, being a South Texas truck all its life and having low mileage. But I do see it as an investment and plan to upgrade a few things, and be sure it's properly maintained. We're having a rainy streak for the next several days, so an oil change is in the plans once it's dry again (I have to work on my trucks in the driveway).

Took your advice and stopped by the local wrecking yard. Found one 3500 and pulled a backing plate off. Here’s a pic of the contact pads. How do you think these contact pads look?

 

[HotWheelsBurban]

Took your advice and stopped by the local wrecking yard. Found one 3500 and pulled a backing plate off. Here’s a pic of the contact pads. How do you think these contact pads look?

A little better than the ones on your truck, all of them will have some wear after all these years. I recommend once you have everything clean and are reassembling the brake shoes and linkage/springs, to apply high temperature brake grease to all the contact points. The stuff I use is Bendix brand, looks like caramel icing. Most good parts stores should have some brand of this in stock. I use a wood popsicle stick(clean of course) to put it on.

 

[GoToGuy]

Bucking in 1st gear is pretty normal for a manual transmission. Holding a constant speed at lower rpm in 1st and sometimes 2nd is going to buck some.

Does it go away if you just throttle through it? If so, I would say it's normal.

No, it's not normal, a smooth start is " two step dance and balance between throttle and clutch" . Yes thier might be the rare, occasional " slip up". A buck and stall the engine. If you think that is normal you need to re- evaluate your technique.
When I rode with nephews in there Japan hot rods they would not bring the throttle in soon enough when up shifting, resulting in a clunk . Releasing the clutch with engine rpm not close to transmission rpm, then adding throttle. "Hey, give it a little more throttle when releasing the clutch try match or get engine rpm closer to transmission rpm ."
Hardest vehicle to ever make smooth start from stop to moving? Three axle tractor with a V12 Detroit? Nope.
A 1963 Corvette roadster. 327,. 365 hp. So featherlight, and so much POWER. Bawaa ha ha!
Good luck!

 

[0xDEADBEEF]

No, it's not normal, a smooth start is " two step dance and balance between throttle and clutch" . Yes thier might be the rare, occasional " slip up". A buck and stall the engine. If you think that is normal you need to re- evaluate your technique.
When I rode with nephews in there Japan hot rods they would not bring the throttle in soon enough when up shifting, resulting in a clunk . Releasing the clutch with engine rpm not close to transmission rpm, then adding throttle. "Hey, give it a little more throttle when releasing the clutch try match or get engine rpm closer to transmission rpm ."
Hardest vehicle to ever make smooth start from stop to moving? Three axle tractor with a V12 Detroit? Nope.
A 1963 Corvette roadster. 327,. 365 hp. So featherlight, and so much POWER. Bawaa ha ha!
Good luck!

When I say normal, I don't mean it's going to happen every time. I mean if you do something wrong, like let the clutch out too quickly, bucking is what happens.

I've been driving stick for 35+ years, and by the far the hardest to launch smoothly was my Firechicken with an aluminum flywheel and a cam that didn't really make power until 4500 rpm.

 

[GreenMonkey]

After doing some research, I’m going to take my backing plates by a shop tomorrow and have them weld a bead in the grooves on the pads. I’ll then grind it smooth and put my brakes back together. It’ll probably be next weekend before I can get it all done since I don’t have a garage and it’s supposed to be raining all week. But I’ll get back to y’all with the results and see if this fixes the locked up wheel problem.

 

[Schurkey]

Most folks seem to weld-up the grooves rather than replace the backing plates.

Worst car I ever drove for smooth starts in 1st Gear was a '67 Camaro with a stock but healthy 454 transplanted into it, a 4-speed Muncie, stock rear gears (3.08?) and the GMPP 13-lb nodular iron flywheel.

There were two ways to leave a stop sign: Bog, almost stalling the engine, or rear tires smoking. There was no in-between. Bog, or burn.

 

[454cid]

The back plates seem to be NLA from GM, and I haven't seen any from Dorman either. For awhile GM backing plates were on Amazon, but went "unavailable" after a while of having them in my cart. They were expensive too.... about $100 each.

 

[GreenMonkey]

Just wanted to update the thread. I ended up having a bead welded in the grooves on the backing plates, grinded down to flat, and rebuilt the drums while I was in there. Truck is operating just as it should now. So I’m assuming the backing plates were the problem. Thank you to the person who suggested the backing plate issue. Wasn’t something I had ever encountered before and wouldn’t have thought of. And thanks to everyone for the guidance and suggestions. Glad to have it back on the road and hope this can help someone else down the line.

 

[fancyTBI]

Great looking truck. Glad you had some success with the repair.

 

[GreenMonkey]

Great looking truck. Glad you had some success with the repair.

Thanks. And it does have a maroon interior