Rob

Exactly. Seat of the pants feel usually means nothing if not backed up with analytical data resolve. Can't do that without test equipment properly calibrated and the output information interpreted correctly. Testing diesel fuel pressure at low idle or no load at high idle will prove nothing as the fuel loading/draw in minimal. Best to throw 20K load onto a truck and drive it hard while watching test equipment for interpretation. Lots can be revealed this way.

always did like the look of most R models due to their classic stance, along with the later "RD", and "RB" series. I still prefer round headlamps but that's just me I'm certain.

What Glenn stated. You need to cut to the chase and get this project sorted. Was the radiator destroyed in the impact? If so you have a real strong possibility of the crank snout being bent. That in itself would wear a damper out very quickly as it tries to qwell the harmonics set up through the rotating assembly. Any glancing, or direct blow, (impact) to a crankshaft is reason for strong suspicion to it's usability as they are very ductile in construction and bend easily. However that being stated, I don't see heavy damage to the front centerline of the truck from your photo. If the end loader did not hit the truck square pushing the radiator into the fan and crankshaft pulley/damper, there may not be any damage there. Easy enough to pull the damper, mount up an indicator and measure runout of the crank snout as the shaft is rotated through 360 degrees.

PMG rather than series wound motor also. The permanent magnets help set up the field to pull the armature around lessening the electrical draw so smaller components can be fitted. Seen some hold up well, some not so well. A good starting engine that is maintained well with let a 39MT live a good life. A hard starting engine will not, as will the severe duty of extreme cold temperatures. I don't have any 39MT so can't speak from direct experience but around here the 40MT is still more popular than the 39MT.

Ohh man is that true. If reciprocating parts are not weight matched during overhaul, all kinds of vibration problems come forth. Is the same shop you are attempting to use the one that did the inframe or overhaul? If so, there may be a hidden story there.

don't think you'll have a 1/2 hour of your time wrapped in this before finding something positive in reference to a solution. Block can be align honed back to new condition if not destroyed. Crankshaft if bent or suffering from fatiigue will need replaced. I don't favor inframe overhauls on off road trucks citing the damage, (twisting usually) a crankshaft can suffer from the severe duty they endure. Kind of difficult to thoroughly evaluate a crankshaft if it remains in the block during engine overhaul.

Get under the truck and remove the dust cover on the bottom of the flywheel housing. Pry the crankshaft with a bar or large screwdriver to the rear. Mount an indicator on the crankshaft pulley/dampner/ balancer and block, then zero the indicator. Pry the crankshaft forward in the block till it seats and note the deflection of the indicator. If this is out of tolerance for crankshaft "walk", you could have either a worn out thrust bearing, or a worn thust surface on the crankshaft. Any shop that would tell me they don't have time would not get any of my business.

The truck is set up perfect for it's dump truck life as is. I don't see where the engine is an EM-6 series and wouldn't push the envelope myself. Stretched rods and parts operating out of design criteria don't tend to hold up too well long term if the envelope is pushed. A swap to a lower numerical number gear ratio is required for additional road speed in this case. The 4.64 Mack rears are very good sound rears in their current application and 4.17 is getting on the fringe for soft dirt work with longevity considered. 4.17's will work fine but not hold up as well as 4.64's is another way to say it.

The only real drawback to the 39MT starter is the aluminum housing. It is best to paint the mounting flange of the starter nose where it butts up against the flywheel housing on anything that is cast iron or steel. The dissimilar metal corrosion starts quickly if this is not protected. Not much of a problem on a hobby truck that spends a lot of time indoors, but a working truck subjected to the elements is quite a different story with road salt etc. entered into the mix. Hard to beat the 40MT starter however it's sliced. Both four, and eight brush variants hold up well for many years and were very common; albeit heavy.

That is the way I t/s also in real time. I do prefer the remote gauge via hose myself but I don't want to get the gent stuck alongside the road someplace while trying to isolate. Plugged tank vents, swollen, or compromised hoses on older equipment, and worn parts are all possible contributors. Basically if the transfer or lift pump pressure cannot be maintained under loading and falls off, the fuel volume delivered to the injection pump gallery is also falling off and the engine will starve which is seemingly the scenario experienced. Easy enough to remove the suction hose on the inlet side of the primary fuel filter and blow compressed air through this line listening for gurgling in the fuel tank. This ensures the fuel line is not plugged or restricted. Most R models had lower sumps in the bottoms of their fuel tanks and would be a good idea to drain this low point to remove any contaminants too. Physically look at the lines to ensure they are dry. If they are leaking any fuel, they are also allowing air entrainment of the fuel supply which is not good. I'd wager he'll be replacing the transfer pump from my past observations. PAI still markets them so not so bad in cost and easy to change in the driveway if need be.....

another thing to look at is crankshaft runout. I've seen the flywheel mounting flange non perpendicular to crankshaft centerline due to wear; (bent crank). An indicator on the crankshaft flange will readily reveal this as the crankshaft is slowly rotated through 360 degrees of rotation. Dirt/rust buildup precluding the flywheel from mounting squarely onto the crankshaft hub/flange will also appear to be an unbalanced condition but this can be seen before the flywheel is removed from the crankshaft. Only time I've really seen flywheel housing wear is when the bolts were not adequately tightened after a clutch change, or missing bolts altogether allowing things to move when they shouldn't. I don't know but it certainly appears, ( to me at least) there have been a lot of variables overlooked in favor of swapping parts on your nickel. to find vibrations which are so deep seated I use a set of glue on transducers/accelerometers and monitor each with a portable oscilloscope individually. This works well but is expensive.

if it were me, (and it's not) I'd get the pan off the engine and transmission out. Using two hydraulic bottle jacks, force the crankshaft up into the block and remove the back four main bearing caps. Then plastigage those bearings for clearance. This sounds like the crankshaft is "wollering" around in the bearings from what I've seen in the past. Usually running like this results in crankshaft breakage and hopefully you are not to the fatigue stage yet. Ensure the bearing clearances are even and there is no scoring. Would be a good idea to roll a new set in if nothing bad or out of tolerance is found. After the main caps are reinstalled, pry the crankshaft side to side at the rear main as there should be virtually no movement. If side to side movement is detected, set up an indicator to ascertain how much there is. Then pry the crankshaft fore and aft in the block again looking for movement, or "walk". Fore and aft movement is usually "shimmed" to tolerance. Gets expensive when you have to pay for the labor; especially labor that is non productive. Far too many "swappers" out there whom read a computer to tell them what to change than good qualified mechanics these days. Your problem seems be into the dynamics of what make the machine operate which are not being evaluated deeply enough.

Hi Tom; Most of those valves only leak during the cold months and are perfectly silent during the warm summer season. I have several in my parts bin of all types and one of these days when I start working on trucks again, I may use a few on a couple projects.....

You are correct but the loose exhaust valve seats did not hold up long before breaking and the engine most times had a definite miss during all rpm's. An overhead run and compression check is first order of business. It almost sounds as if the solenoids for the "Dynatard", (if equipped) are "hot" all the time rather than selectable via a toggle switch on the dash.

While this is a good suggestion you need to go further. Plumb your gauge into the system and measure the pressure at low idle; then measure the pressure at about 1800rpm. Then with a helper monitoring the pressure gauge and the brakes set on the truck, slightly accelerate the engine while slipping the clutch to load the driveline. Not hard enough to smell the linings get hot but enough of a draw on the engine to load it. Ensure your monitored fuel pressure remains above 18psi at all times. Continue to monitor this for about a minute then let off, shut down, and allow things to cool about 15 minutes. At the end of 15 minutes, look at the pressure gauge without starting the engine. If it is a zero reading, consider rebuilding or replacing the transfer pump mounted to the side of the injection pump. Chances are the valves internally are compromised, or the piston is worn in it's bore which there is no field repair available; only replacement. Use a liquid filled pressure gauge or it will not last due to engine vibration.

A piece of 4" X 6" .250"-.500" thick silicone rubber cloth sheet is an effective isolator for the rumble from the cab supported exhaust stack. The original rubber sheet used becomes hard from age/exposure and is ineffective. A stainless flex pipe installed under the cab into the exhaust pipe is also effective and the combination of both together yields a very near resonate free exhaust system.

Ensure the valve clearances are correct meaning run the overhead first to ensure it's accurate. Verify you do not have a "Dynatard" engine brake installed without the appropriate operating gear in the valvetrain. "Dynatard" has oil solenoids on the valvetrain and they do some funny things if not set up right.

Pretty common once the valves are a few years old due to the hot/cold cycles the cab endures. I think it's an "R7" valve but you'd need to check as I've been away from trucks for a while. O ring kits are cheap but the valve is usually about $20.00 so not really worth rebuilding, (to me) locally. Sorry for my inaccurate post but the valve is either a PP-1, or PP-7 and not an "R-7" as I posted earlier. R-7 is a relay valve. PP-1 is the most common to release tractor brakes and PP-7 is for charging semi trailer brakes.

Pulled the plug with 34 years exactly yesterday. Done; no regrets, no looking back. Hoping to get some time in on my trucks with no job getting in the way of the hobbies. Rob

Yes, from my family to yours hope your holiday season remains bright and the new year brings good health, prosperity, and happiness. Rob

Not too difficult to repair properly once the offending material is removed but someone certainly didn't know, or didn't understand the dynamics to correctly to modify truck frames.

Think I've seen that one too at one time or another. Not familiar enough with any area of Chicagoland to know where however.

Yes, that was common. If you removed the "Speedi-Sleeve" from the drives they could, or could not be factory supplied when new. Replacements should be readily available. There is a tool recommended for their installation but I've never had one myself. Have always used a block of wood, (usually oak) and drove the sleeve on slowly and evenly. Put a thin layer of grease on the seal riding surface before sliding the hub into position so you don't burn the seal lips up during initial start up.

I'm not familiar with a tool needed to reinstall the sealing ring. It should have an "O" ring on it's inner surface which bears against the spindle and most have a roll pin which engages into a hole in the spindle to keep the sealing ring from spinning from seal drag. Some of the sealing rings from OEM were a press fit and the roll pin was not there but one would bore a small hole into the area where the sealing ring abuts and the replacement seal ring would slide right on. Some factory installations had a "Speedi-Sleeve" installed already. Those you just tap into place with a block of wood being easy to not distort it as you drive it onto the sealing ring. A little here, a little there, and they usually just walk right on.

In my experience with them they will not save fuel or boost economy. When they are adjusted and working correctly they limit off idle torque rise in the lower gear or two and reverse. This has saved many a driveline when loaded heavy and in soft ground. Also helps out a bunch with hired drivers whom don't have to pay for parts when the fail. Ensure the reversing relay is operating correctly by plumbing a pressure gauge into it and the air cylinder on the trans is not leaking internally if so equipped. You need air to the reversing relay from and air receiver, and manifold boost for the relay to cause the cylinder on the pump to operate correctly along with the shims to allow proper rack movement.