HK Trucking

CB radios pose no problem because they are not "chassis grounded", that is why they have a red (+) wire and a black (-) wire. The outside case of the radio is not "hot", or "grounded". What I was referring to was AM - FM car radios when used on a positive ground system by hooking up the truck's "hot" (-) wire to the radio case, and hooking a wire from the radio input lead to the truck's "ground" (+). In that scenario, the radio's outside case MUST not be allowed to touch any metal part of the truck, or a dead short circuit will result. In addition, as I stated previously, if the AM - FM antenna is mounted on a metal part of the truck which is grounded, then it will ground back to the AM - FM radio thru the "armor" portion of the co ax cable, causing a dead short also. Either the antenna must be insulated from ground at it's mounting point, or else you can strip off a small section of insulation from the co ax, and remove a short section of that outside braided wire that's just under the insulation, which will prevent it from grounding back to the radio from the antenna. After removing the section of braided wire, wrap the "modified" area of the co ax securely with electrical tape. I've done it that way back in the 70's, and although there was a decrease in the FM reception after isolating the antenna from ground, that was certainly preferable to a dead short.

That would be my suggestion too. He should choose a wheelbase dimension short enough to allow all of the bolts in the trunnion stand to be located in the original frame, then add frame rails rearward from there to the desired length.

If it has a switch on the clutch pedal, then it's a Jake brake, not a dynatard. The Dynatard did not need a clutch pedal switch because the actuating switch in the governor turned the Dynatard off when the engine dropped to idle and the governor pushed the rack open for idle fuel, so there was no possibility of the Dynatard "stalling" the engine, hence no need for a clutch pedal switch. Dynatard and Jake brake circuitry is completely different. That said, if there's no power at the dash switch, start there. Check fuse or circuit breaker in that circuit, or look for a broken wire . If still no power to the dash switch, run a new power wire to it from a fused source and abandon the inoperative power wire. Check to see that the switch has continuity in the "on" position. Work your way on down the line, check for power at clutch switch, throttle switch, and at the terminals at the Jake spacers between the valve covers and the heads. Make repairs as necessary to achieve this. With dash switch on, clutch pedal up, and throttle at idle, you should have power all the way thru the system to the terminals on the spacers. Once you get this far, then try the Jake with the engine running, it should work, if not, the wires inside the Jake spacers could be broken, or you have defective Jake brake units. Last I heard, overhaul kits are still available for those Jake brakes.

Most of us here are fully aware that Mack trucks have always been available with vendor supplied engines, transmissions, rears etc, if the customer specifically ordered the truck with such components. That said, when Macks were equipped with Cummins, Cat, or Detroit engines in the past, the engines weren't painted a different color and called a Mack engine, such as what's happening now with the MP7 and MP8 which are Volvo engines simply painted a different color and called Mack engines.

....And this is relevant to the quote you used from my post how?????

You're right. You actually have to have a sense of timing with the 5, 6, and 7 speed transmissions. With the 18 speed Fuller (and it's sisters, the 8LL, 9 speed, 10 speed, and 13 speed, if you just move the stick as quickly as possible to the next gear, you can upshift successfully.

How would that cause the front brakes to overheat? With the switch in the dry road position the front brakes work normally, and with the switch in the slippery road position, the air pressure to the front brakes is reduced to avoid locking the front wheels on a slippery road. I fail to see how could have caused the front brakes to overheat.

Well, at least that's got a .60 overdrive, but the low gear ratio of 5.24 will certainly leave him paralyzed when off road.

An unsynchronized transmission is actually a safety feature. The transmission cannot accidentally be put in the wrong gear while going down the road. Think of it this way: You could drive a manual transmission car down the road at 60 MPH in hi gear, and due to the fact that the transmission is synchronized, you could depress the clutch pedal and the synchronizers would make it possible to shift into first gear with no problem (keep in mind the car is going 60 MPH) So what do you think happens when you re engage the clutch? Yup, massive overspeed of the engine, shock to the driveline and more than likely catastrophic damage. Now picture that scenario in a 80,000 lb truck with a synchronized transmission. I think that's one good reason why class 8 truck transmissions are not synchronized.

There it is in a nutshell. Check out the Volvo and Mack Trucks corporate websites and look at the engine photos there. Notice that the photos of the Volvo engines are all right side views. Notice that the photos of the "Mack" MP7 & MP8 are all left side views. That precludes the possibility of unsuspecting prospective truck buyers of looking at the photos side by side and noticing that the only difference between the engines is the paint color, and a tweak or two in the ECM. Does anyone here know the exact date that Volvo acquired Mack Trucks Inc? I believe that date should be declared a national day of mourning, to be observed yearly in honor of the Greatest Name In Trucks.

But at least when Renault owned Mack, they had sense enough to leave the class 8 Mack trucks alone, and let the American engineers call the shots.

That 6 speed is a TRXL107A, direct in hi gear. Maique stated that he currently has a TRQ7220 in his truck, which is a double overdrive transmission with .70 overdrive in 5th hi. If he were to remove the quad box and install that 6 speed, the road speed in hi gear would be greatly reduced. Running with that 6 speed in hi is direct drive. Running the quad box in 4th direct is direct drive. Therefore, whatever top speed is obtained in 4th direct with the quad box, will be the MAXIMUM road speed in hi gear with the TRXL107A Of course the rear ends could be swapped for the proper ratio to work with the 6 speed, (Usually 4.17) but this is starting to get expensive!!!

If you isolate the AM/FM radio from vehicle ground, you've got to keep the antenna isolated from the vehicle ground also. If the antenna is mounted to metal, it will ground back to the radio thru the coax cable, and fireworks will result. Isolating the antenna from ground does reduce FM reception somewhat.

That's an E7 400 mechanical with a T2130 Mack 13 speed. Straight pipe of course!!!!

You've found an adapter for what trans? You say you've found an adapter, and in the next sentence you're asking if anyone has a 12515. An RTO12515 wouldn't need an "adapter", but you would have to make sure you get one with a bellhousing that has the Mack mount setup on it. Then, after G.G. questions why you would want a 15 speed, you ask if anyone has a Maxitorque trans lying around anywhere. This thread isn't making much sense to me.

Don't we all! Or better yet, the ENDT673 - TRQ7220 days!!!!!

I'd leave it at 130. That extra 10 lbs. pressure isn't going to hurt anything, and it will give you an extra reserve of air.

The MP7 and MP8 are Volvo engines with Mack specific programming in the ECM. IMHO, Mack is headed for extinction just like all the other brands of trucks and heavy equipment that Volvo has "acquired" in the past.

TR = Transmission T = Triplex L = Lightweight version. (Aluminum top covers) 72 means it is direct in 5th. (hi split in the compound is overdrive) This is known as a single overdrive triplex. It is a 15 speed. (can also be split shifted in 5th just like in the rest of the gears. I believe this is the same as the transmission in Larry "Freighttrain's" B61.

That would be a TRQ77 or TRQ770 quad box from that B422. It's a much lighter duty transmission used behind the smaller gas engines and END 465 and END475 diesels.

Thad, try putting a socket and breaker bar on those bottom generator bolts and get them turning while repeatedly soaking them with PB. Once you get them turning freely then try driving them out with a hammer and punch.

The bottom one to drain it. The middle plug is usually a port to install a sensor for a differential temp. gauge, and if your truck does not have that gauge, then a plug is installed in that hole. After you drain it, replace the bottom plug and refill with the recommended gear lube until the lube is level with the top hole.

Then it really doesn't make any sense to go thru all that BS just to put an automatic in that truck. IMHO, it would make more sense to run that truck as is until you are ready and financially able to upgrade, then if you really want a truck with an Allison auto, buy one that's already equipped that way, and be sure it has at least a 400 horsepower engine so you can kick some ass.

5 speed - single stick 6 speed - 2 stick (although Mack did offer the TRXL 107A & TRXL 1071A 6 speed which was a single stick with an air shift knob to shift the Hi Lo Rev compound).

If it's a DM 685, then someone must have swapped that quad box in there, as the "685" denotes a Maxidyne equipped truck which would have a TR 107 series 5 or 6 speed transmission. (TRL 107, 1076, 1078 5 speed, or TRXL 107 or 1071 6 speed). These would have been the OEM transmissions for a 1974 DM685. 66 to 71 models would have had the TRDXL 107 or TRDXL1070 6 speed. (The TRDXL1070 was an overdrive trans).