JoeH

Having trouble seeing exactly what's going on with the bolts... One sheared off and the other walked out?... They're supposed to have locktite on them I think, so they can't walk loose.... if they walk loose they're subject to all sorts of fatigue as the engine/trans flex under power. It's not "normal wear and tear", I'd suspect it wasn't put together properly when the trans was replaced. We're getting ready to retire our 1979 mack, it has a trans bracket that keeps coming loose on the aluminum bell housing. 1 bolt hole is stripped out and the other 3 keep walking out.

Google Street View of the intersection doesn't show any low ground clearance signage, I'd be harping after the municipality and CSX that they should have had signs up with minimum ground clearance requirement signs. I've never driven a low boy, but I have seen ground clearance signs for exactly this type of thing...

The gal in the car summed it up about right: "oooohhh noooo....."

He probably has big brakes. Our 1980 dm686sx has 18"? Brakes instead of the standard 16"? Brakes. Truck always had great stopping power. I wish more trucks had them.

Anyone else cringing that the company mechanic tightened down on that one valve not once, but twice?... @Joey Mack is beyond edumacated on these engines, it's crossed my mind to try to convince him to drive to PA if I ever have H ring issues on my 2003 ETECH.

The same gasket is used on the E7 motors as well as some ETECH motors. Bolt pattern is identical, you should have no problem getting one for it from your dealer. However I can confirm they're $2k, we put a new one on our '95 E7 a couple years ago. Note the PoS will have pin holes in it that require a newer style rubber gasket with tips on it that pole through to aid with gasket alignment. Some of these holes will leak oil if you try to assemble them with the old cork gaskets.

We also had a valve seat crack and drop into a piston on the same engine, where it chunked to bits and got lodged in the piston head. Damaged the head, ruining the core. It's time consuming, but if you don't find anything obvious with valve lash then pull the heads. Just don't set them face down on the table, the injector tips stick down into the piston bore.

Does it have Jake brake? If so, inspect the top of every exhaust valve for the disc spacer that rests on top for the Jake pistons to push down on. Our '79 endt676 has a weak valve spring on one valve, that disc kept popping out. We deleted the Jake brake after the second time it did it. I'd walk the engine round again slowly and feel for excessive valve lash. Carbide face may be missing off one lifter tappet, starting to wipe a lobe off the cam.

Did you lubricate the fuel filter o rings on assembly? Dry filter o rings could have bunched up, allowing it to suck air.

1979 R686ST This guy is likely getting retired in June while there's still something left to restore. Where do we get cab repair panels for it? Roof, sections around rear window, gutters.... Undecided if it'll get a 5th wheel or a coat of paint inside & out on the mixer body. My dad bought the mixer in 1976 on a different horse, and the truck in 1987 when the old horse died. Both truck and mixer are good talking pieces, & you'll be hard pressed to find an older volumetric mixer than this one. (It's a 1968 Daffin. Volumetric Mixers were invented around 1962)

If it does it again, wiggle the fuse for the EECU. My 2003 ETech had that problem, yielded a code 9-1? Or 9-4. I forget which code number. It's "engine power loss without key"

Serial number will matter too, different years have different modifications. Could be different gear ratios used in same model trans.

Any shop you hire will need tranny model and serial # so they can order the right stuff. "5 speed maxitorque" is like saying "I have a car, what oil filter do I need?"

I wonder if you're going to run into issues with the front spring brackets. The crossmember bolts to the inside of it, may be different. Your picture looks like the crossmember is between the damper and timing cover, whereas my '95's crossmember is in front of the damper. The engine rests on a shelf welded to the backside of my crossmember. This swap might require different front spring brackets.

We had to delete the engine brake on our 283 however, because one cylinder has a weak valve spring and the spacer that rests on top of the exhaust valve kept popping loose. After the second time we pulled the Jake off. If you have 50-80,000 hours on your engine like we suspect our has, then you may want to replace valve springs if you add a Jake brake.

Having driven a tandem axle with the same setup for some years, I would steer you away from a trans swap and into a Jake brake for faster shifts. Your engine makes 90%+ torque across an 800+ rpm powerband. Extra gears are wasted on this engine. The 8LL is designed for engines with a 4-500 rpm powerband. Faster shifts, however, help you catch the next gear while you're still in your 90%+ powerband. You'll also be giving up your multi speed reverse, which let's you crawl up a mountain or fly across soggy ground. But at the end of the day, you know your workload conditions and needs better than me. It should be a doable conversion if you have access to a good Mack junk yard.

You have to stick to an E7, you cannot use an ETech "E7". However if you had all the right components plus the know how, there's no reason you couldn't transplant a running ETech engine into the truck... But I wouldn't. What failed, the head gasket? If that's all, then I'd just be pulling that head and replacing gasket. Better to stick with an engine you know is good (albeit with a lot of use) than trade for one you don't know...

@Keith SS report to the managers office...

Change the bulb in your lightning bolt.... You could have engine codes that we can diagnose through that light if you can get it to work.... Key on, if the lightning bolt is in, you press and hold the cruise set/decel button until it goes out. Then count the flashes to get a 2 digit blink code. Press the set/decel again, if there's another code it'll spit it out too. Keep doing that til it starts repeating itself. Note that you perform this procedure with the cruise control "off". Engine can be running, or not. Tell us the blink code and we can stop guessing.

You probably have a fuel return line leak. The plastic lines on top of the head that go from injector to injector are prone to leaking. Any dampness up at the injectors is likely caused by the plastic lines failing. Also if any of the hard metal fuel injector lines have dampness at the ends then you can lose prime and have hard starting.

State trucks (In northeast USA) are all overpriced junk with so much rust from salt work. Not worth looking at. Truck Paper is a great app to scout what you're looking for. R(D)6xx"P" would be a single axle, R(or RD)6xxS(or ST) will be tandem axle from factory, but may have a liftaxle as well. xx is in place of either 85, 86, 88 or 90, which tells what engine/fuel characteristics the truck has.

Look for a truck with a good cab and good frame. Everything else can be rebuilt.

Truck is working well; concrete season is over, now we have to keep our heads low to pay off the mixer over the next 4 years. This is our current project we've been working on. Hopefully we can get this mixer rebuild completed sometime in the first half of 2023. Less Mack related stuff on this build, so it probably won't find it's way onto the forum. The horse is a 1988 RD690S with an EM6-300L.

Probably torque rating.

Pretty sure they "crush" a little to seal. So you get one "crush" out of them.