seyser

That's good advice! Pretty much confirmed my plan to start with new. I have a number of weeks until harvest so shouldn't be an issue to get it done.

Correct yes the front drive axle. I would have to follow the other lines but I know one or two go back to another relay for the brakes on the rear drive axle. After first applying the service brakes there is air coming out of this plugged port regardless if the pedal is pressed or not. I assume it should only be pressurized when the pedal is pressed as to activate the brake cans.

I have what I believe to be a faulty front relay valve. When I first air the truck up and release the parking brake I can move the truck as normal until I first press the service brake then the brakes are locked on. We removed and capped the air line that goes from the relay and feeds the front axle and then the brakes act as normal. Does this sound like a bad relay valve? I found the same one on ebay and it should be here today. Haldex 28071. When I remove the nylon air lines can I reuse them as is or do they need to be cut shorter with a new ferrule added? They are already as short as can be so that would involve making a junction on all lines or replacing the whole length which I hope I don't have to do.

I appreciate all of the good information. Although I agree having spring brakes on both axles would be ideal, I will probably run it as is. I filled a couple of hubs with oil and will have to monitor those. I imagine they will need a new seal. I didn't actually measure the brake pads but I see the drums have quite a lip on the outer edge and plenty of groves where the pads run. My thought was to just install new pads, drums, and replace leaking seals and it would probably be good for my lifetime. This trailer will easily see less then a thousand miles annually.

Thanks for the reply and all good information. Here are a few pics of the axles.

I recently picked up a hopper bottom grain trailer and was wondering how to identify what axle(s) it has? Its a 1995 model year but the builder sourced used cutoff running gears at the time. This one is spring suspension with budd wheels and no ABS. I looked briefly for a tag but didn't see anything affixed to the axles. I will post a couple pics later today when I'm near the trailer. I don't have much experience with commercial trucks and trailers so trying to learn what I can. What is the proper way to find the correct pads and drums it uses? Do I have to remove the drums and measure them to confirm the correct parts? How about pads? Also I see I might have an axle seal or two leaking so would like to possibly get those on order as well but want to make sure I get the correct part. Can anyone recommend a quality pad and drum brand? Prefer USA! Iv read Gunite, Webb, and Stemco Centrifuse as a couple drum manufacturers. Thanks in advance! Jeremy

Larry - I think you are on the right track. A cable setup might be your best option. It sounds like you have already shimmed the current linkage and still not seeing positive results. The cab and engine will always move independent of each other and I wonder if that gets amplified as motor and cab mounts get worn out?

The trailer is a HART brand and was built in Webb IA. This one is a 34' and will mainly be a field to farm trailer. I'm not against keeping tube type tires on the steers. My only reason for wanting to change these out is because they show some cracking and I cannot read the date code so I would rather be safe then sorry. I have a pile of 22.5 rims so it wouldn't be a huge deal to blast and paint a couple and update to 22.5 tires. I'll have to look into prices and compare 10.00x20 vs 11r22.5 and decide from there.

Thanks everyone! I would eventually like to paint the centers black and the wheels either white or silver. I mostly plan to keep it original. The truck is a legit low mile truck with 118k miles and 4400 hrs. I purchased it from the original owners widow. It was a one owner, one operator truck that was used to pull a lowboy. The white paint is original and the blue accent was painted at Kansas City Mack before the owner picked it up in late 79.

I purchased this 79 R model about 5 years ago to use on our small farm. I had planned to find a hopper at the time but unfortunately that never happened and the truck was tucked away in the shed. Fast forward 5 years later and I finally purchased a trailer. I pulled the Mack out last night and hooked it up in the yard to see what it would look like. This simple setup should be a nice asset to our farm. The Mack needs a few things including a brake relay, fluid changes, and probably update the front steers to tubless 22.5's. Anyways here are a couple pics:

Thanks for posting. I looked on his profile and it looks like he hasn’t visited since late 2023.

I have been browsing ebay but no luck yet. I'm not very active on facebook but will have to see if I can get on there and track something down.

The driver seat bottom in my 79 R has seen better days. It looks like the seat is a Bostrom Level Air. Was wondering if anyone would have recommendations on a replacement cushion/foam? I would like to keep it pretty original looking if possible. The seat back and pass seat are all excellent as its an original low mile truck. I know most people will recommend an upholstery shop but just looking for any replacements if possible. Thanks -Jeremy

Looks great!

Keep up the good work!

Seems like a pretty fair price for a V8 Mack.

Bidding closed. $11,250.00 high bid.

Ah yes, that makes sense. I was always curious why the different setups. Didn’t event think about the cab being hinged and constantly moving.

https://minneapolis.craigslist.org/dak/hvo/d/jordan-66-model-mack-wrecker/7051842320.html Saw posted on Craigslist

They must have used different setups over the years. My 79 R has flat metal plates on the cab side and round rubber hockey pucks on the hood side.

Good work

I suspect the block heater plug was dealer installed on most if not all trucks and was placed in the location at the discretion of the dealer.

Pretty ironic to run across this post. I also just stumbled upon his channel a few days ago. The R video caught my attention.

1979 R686ST

Keep up the good work!