1989 Peterbilt 379

Rear ends...Drain fluids and remove pumpkin and inspect teeth. Check the rear end filter also (if it has one).
fFifth wheel stretch test? You will need a special tool to check that. Napa has one. But if you don't know how to inspect them, pay someone. You don't wanna lose a trailer.
Trans? drain and inspect fluid. Is it sloppy?
Electrical wire inspection for the harness? Check for chaffing on wires that cause shorts? USually a 1500$ job for a new one installed.
Cooling system? Water pump? Water lines dry and cracked? Clamps old and rusty? You'll need all new ones.
in-frame include all the engine accessories? Ac compressor, alternator, Fan hub, turbo, air to air system ..
Then how is the suspension? Springs bent or cracked?
Air bags leak?
Shocks leak or weak and completely out of fluid?
Rubber bushings on suspension cracked or missing?
Cracks in the frame due to rust? Hows the rust on the frame???
Start with First draining and analyzing every fluid and go from there...
Do a COMPLETE and major maintenance...
Do a dyno test on it??
Front end king pins and bearings weak and lose?
Steering components weak or lose?


Go thru all those and then we can start on the heating system inside the truck, go thru all the buttons and switches inside and that should keep you busy awhile.


PS dont forget the brakes, tires and seals all over the place....

 

To answer your question quickly:
Your truck has exceeded its mechanical limits according to the engineers who built it.
Which means it could and will need a complete over haul. Does that mean they are right? NO. It all depends on its history.

Its hard to say.

With all that bad news, here is some good news.

Your truck has no EGR.
Your truck runs now and is reasonable to repair and turn into a great otr truck.
Interior is all cleanable and replaceable for cheap.
Paint is a one week job if you have a shop and do all the prep yourself and hire someone to shoot it with new signal stage paint. It will look like a new truck. Then paint the frame after you have it blasted of old rust.

You can make this into a great truck for a low cost and good news is you can get your money back from it when your done. hose trucks hold value.

Unlike My freightliner. I have dumped endless amounts of money to go over all the above listed items and it runs like new and handles like new...yet its still only worth so much cause its a columbia.

 

minimal, if htey are leaking id replace them

 

the bags them self should not leak at all. but if its a fitting then as long as your not out of air in 24 hours then your fine.
thats the rule i use. if i hear it and can find it right away, i fix it right away. if i cant, i let it go for awhile till i lose all air in a night. then i get anoid and you will see a guy with a large tool box of tools on the ground and him in a mech jump suit climbing under, over and in the truck trying to find it and fix it lol that be ME.

 

I would need to know how long it has been sitting, or has it been in constant use, the absolute worst thing you can do to a truck is let it sit. If it sat 6 months or more I would say you will have seal issues, the more you work it the more it will tell you.

 

I have an 84 359 with 950,000 mi. It was sitting in a barn for 12 yrs. Has only had bearings rolled in. Drives like a dream and will go 5-7 days without losing air. Everything works but I did replace a couple air bags and a spring hanger and pins.