Geoff Weeks

Most have already made most of the important points. To outfit a truck to do 40% grade with that load, would make it useless for other tasks. Meritor planitary hub rear axles with a deep primary reduction at the differential and then calculate the needed transmission reduction. Torque hubs put the final reduction at the hubs, the axle shafts will not see the full torque required, as would be with any conventional diff, of either single or double reduction.

Mack was indeed the 1st air to air charge cooler with the Tip turbine set-up. Front mounts required a re design of the engine bay/front of the truck, which is why engine mfg resisted it for as long as they did, it would limit what engine could be placed in a truck already on the market. It is why Cummins went to"low flow" cooling, to allow better charge cooling without changing the front end of the truck. You could get a high HP Cummins in a truck that couldn't take a high HP Cat, because the Cat required an air to air over 400hp. When the truck models got re-designed, the new designs all allowed room for air to air, and the "work arounds" like tip turbine and low flow cooling were quickly dropped in favor of the air to air in front of the radiator. Front mounts allow large surface area and are simple to cool, using the radiator fan, so when room was allotted for them in truck design, that is what everyone switched to. The Mack tip turbine was a very clever answer to the problem and compact. As an engine mfg it is hard to sell an engine to a truck that would require special front end designs to take it, so work arounds were used. It was clear that front mount air to air was the future of all engines and when truck models were updated, room was allotted for the air to air.

Depends, on type and which adjustment you are talking about. If you are adjusting for wear at the ball socket, then no. If you are adjusting for length then it depends on how the drag link is made. Some like my Marmon use a mini tie rod with left and right threaded ends, and that can be adjusted for length without removing an end, others like my IHC's and I think yours (hard to tell from the picture, but it looks to have only one thread) you have to remove one end to thread it in or out.

It varies by state, some do not allow you to keep a CDL at all if no med card (I think it is either AZ or NM) but under the Fed rules that most states use, you can run personal stuff and some excepted vocations, like here Propane del and AG chemicals are on the list. either intra or interstate excepted. A state can have stricter rules than the Feds but not more lax. The above states (and I can't remember which one) went stricter and you can't hold a Class A or B without a med card. So to be sure, you have to check with your state on what is allowed. When I retired, I change to interstate excepted and have my "CDL" or class A without a med card. If I were to go back in the seat, I would have to get a med card and go file it at the courthouse. Here, anyway it is called self certification, and you have to file it where you get your CDL lic or renewal. In Iowa it is at the county courthouse.

Rockwell made their own "top losding double reduction rears, are you sure they were not those models?

I think it comes down to the vendor that made them. I know that is the way it is on other makes. Being Mack rears are Mack only, I can't be sure. I've had IHC's with both types, and in the book, it stated it was who supplied the housing to IHC, other than that there is no difference

If there is a RPC in BOTH the outlet of the hydrovac and the outlet of the master, the brakes will drag esp after a bit of use. Some Hydrovac don't have a RPC in them and need one in the master. Other do have the RPC in the hydro vac and need a master without the check. The RPC keeps a little pressure in the system to keep the wheel pistons from being pushed back all the way in from the brake return springs. The hydrovac works by sensing input pressure and adding boost based on the input pressure. If the hydrovac is set up with a RPC in the outlet, and a Master Cyl is used with an RPC, there will always be a little inlet pressure and this will cause the brakes not to release properly. If you seam to have dragging brakes or brakes that will not fully release, with the 661 master, then take it a part and remove the metal disk thing at the very back of the master, behind the big return spring, that will "convert" the 661 to a 2657. The castings, bore and stroke are all the same.

The Master cyl pictured is a very common type, BUT there are different bore (may be stroke) and very important, with and without RPC (residual pressure check). If the truck doesn't have a frame mounted hydrovac booster, you need a master with the RPC, if it does have a hydrovac, it may or may not (depending on the booster) need a RPC in the master. The K-7's tha Jojo and I have are a 1 1/2" bore and do not have a RPC in the outlet. It is MC 2657. the same master with the valve is different, I want to say, MC662 but that is just from memory, so could be wrong. edit: I was wrong MC 661 is the number 1 1/2" bore with Rpc. You MUST use the correct configuration for your application and can not use "looks" alone to select.

coupla ways to determine what the truck is now. Some are not 100% fool proof, but will give a good indication. 1) 1st and foremost, look to see if it has an alternator. If so, which polarity is connected to the frame. If it does, it doesn't matter what the truck was originally, but does matter now. Hook the battery up backwards and you'll destroy any diodes. 2) assuming it has a generator, install a battery (it will not hurt a generator if the battery is "backwards) and turn on every load you can think of and look at the ammeter. If it points toward discharge, then you have it correct, if it points toward charge then it is backward. Be sure to disconnect any radio or other complex electrical component before connecting the battery. 3) often times generator voltage regulators are marked as to polarity. Whether the marking are still readable after all these years, is another matter. 4) some electric gauges for temp, fuel etc, will try and read backwards, go below the low stop when hooked to reverse polarity If it has a generator, and no indication above helps, it doesn't matter other than "looks" for period correctness, it can run either polarity (have to repolarize the generator for the polarity you choose) but neg ground affords much more options in today's world than positive ground.

Most common failure is leaking out the exhaust, either with the valve open or closed, next common failure is leaks to the trailer side with the valve closed. Whether a rebuild kit will solve the problem depends on the state of the casting. Sometimes where the valves seat get worn/corroded and a "kit" will not solve that.

HOLD on, what year truck are you working on? Is it pre -121? It could be a TP-1 (not sure, never seen one, as they were out of production long before anything I had). TP-1's and TP-2's are out of production and even rebuilds are NLA as far as I know except for N.O.S. There is a TP that does look similar but is newer and has a double check function built into it. TP-3's and later (post -121) valves all function different than the pre-121 and are not directly compatible. If your supplier went off looks alone, it is very doubtful he will get the right part. It is VERY important to get the right valve TP-1 and -2 have the trip function (air pressure trip to close the valve) in the TP valve itself. The supply side is ALWAYS connected to tractor air at all times. The later TP-3's and up the trip function is in the dash button, and supply air goes through the dash button to the TP, which then opens, anytime it see's air pressure on the supply line. A TP-3 has four connections a TP-1 or 2 has five. There is a later TP that also has five, but has two supply lines, and a double check in it. That valve looks similar to a TP-1,or-2 but functions different. We need to know what you are working on and preferably numbers off the valve to be sure. edit: Whoops, I missed the title (I'm going to blame on the time change!) and see it is post -121! I found some pictures on line that look like it. It is a Midland TP valve. The top connection threw me because Bendix early valves are like that. I didn't see many Midland valves in my work. More info and pictures would help. The above mention of TP-1's got me on the wrong track. PS early (pre -121) are sometimes called "3 line system" and later (post -121) are called "2 line".

I know how you feel, I have a drag link socket in my tool kit somewhere. However, the O/Per is working on a 1996 model, and I have never seen a adjustable link that late. even by 1969 they were not seen on most new equipment. The British buses I worked on were the newest thing I saw with adjustable ends, and they were in the 70's vintage and older.

I haven't seen an adjustable drag link on anything modern, they were more common in the 50's. Goggle "drag link socket" to see the correct tool to adjust them.

Took mine to town with a load of brush the other day. Ran sweet. I'll need to go again soon and get some lengths of conduit.

Most will be wired to the key switch, so the read nothing when the key is off, otherwise they become a slight draw on the system.

Yes, many starters of this era used inertia drives. they get "thrown" out into the ring gear by the starter starting to spin. They have a large spring that can break, esp if the truck was 6 volt and now is using 12 volt through the same 6 volt starter. Pull the starter and look at the starter and ring gear for damage.

The biggest improvement to ride quality was the elimination of B-B length laws. My back-up tractor was spring and if loaded correctly road as good as the other two. Belly load it and it would beat you to death, split or uniform load the deck and it road fine. Even my Fleetstar with walking beam would ride well loaded, but with the short wheelbase and light tractor, would launch you empty over the bumps. It only have an old Viking T bar seat. One thing that has not changed much over the years is unsprung weight. That is where the "rough ride" of a truck can not be eliminated.

Fact is, Mack missed out on the Big Power market when they didn't move forward on their "Big Six" prototype sitting at the museum. Their E9 V8 is the only real Big Power option, but all I've heard is parts are hard to get and they suffer in the longevity department. Whether that's just scarcity and age or design flaws, I couldn't say. I have heard that V engines' main flaw is that they have to run 2 connecting rods on each crankshaft offset. Big power and the costs: Mack V-8's aren't as common because they cost a premium, same as the K-19 and the 3408. Parts are harder to come by because fewer were made to begin with. The K-19 is still made or was recently (Q19) but not used in road trucks, the 3408, V8 Cummins and the like were dropped as they didn't have large sales to continue there development. The V Detroit 2 strokes were around until the end of the 2 stroke. The Mack V8 was well respected, but its higher costs didn't make sense in the days of 55 MPH, but the time that went away we were on the cusp of the electronics and the same power from smaller displacement 6's. When the Big V's ruled the high hp truck market, the other driveline components weren't generally as strong as what came later, that left broken trans and rears if pushed too hard. It wasn't until the 80's that those components were beefy enough to take the higher output. Yes, Mack had their big rears, as did other mfg, but they weren't highway geared, for high speed and high torque. Remember the SQHD (sure quitter's) ?

I remember when we were told that we'd all be driving small displacement engines with lots of gears, Cat pushed the 3306 and Cummins the L-10, but they were coupled to 9 or 10 spds and were slow. Top power was around 300 for either, or about what the E-6 was at that time. Don't get me wrong, these smaller displacement engine today have impressive power for their size, but at the time they came out it was poor. Turning up one of these old small displacement mechanical engine is a courting disaster. Once the electronic's and stronger pistons and rods come in, they did produce a lot of power. Big power has always been available to those willing to pay. 12V-71, K-19 and the Mack V-8, but there was a huge price to pay for the privilege of being the big engine on the road. It came up front in purchase price and continually in fuel and maintenance. I have never been a fan of V engines, and have never owned one in a truck. Most engines will take 10% over what the factory rated them for without too much trouble, once you start trying to push over that, it can really take its toll. Some look at today's electronic engines of about the same displacement and say 'if they can get that out of the same displacement, why can't I with my older engine of the same size?". But that fails to understand HOW mfg got to where they are and the changes needed to get there. Not only are the mechanical pieces stronger, seal better and take heat better, the electronics which allow injection timing to be idealized for the condition also allow it to not over-stress at low speed but still take more when it can. Mechanical, you don't get that ability. you have to make compromises. The Detroit 60 series was the 1st to show what electronics and smaller displacement could do, in terms of hp. just as the Maxidyne showed what a broad torque curve could do decades earlier.

Wind resistance and wind direction can have more effect than weight. When I pulled 48K+ re-bar loads, my mileage was closed to what I would get with an empty trailer. Sure it pulled the grades slower but it also rolled along on the down hill side much further without needing throttle, was less effected by wind gusts etc. Because wind resistance goes to the square of speed, a little increase in speed makes a big difference in power required to move at that speed, and of course fuel to to get that power.

Power is something that will never be satisfied. I'm old enough to remember trucks pulling Snowshoe or other eastern hills at 25 mph, That was the norm, and "O/O hot dogs" may blow by you at 30-35 mph. Today you'll be a hazard pulling the same weight at the same speed. The 670 +/- CID of the Mack was quite impressive for what it was, and put up against Cummins and Cat's of larger displacement. I was called on to work a train de-rail by a company I used to work for. (I was my own carrier at the time) and when I found out where and where we were to move the damaged cars, I got my Fleetstar with a 6-71 and left my 9670 at home. The other O/Op's were laughing when I showed up, but soon their tune changed when the found out we had to go down the access beside the track. I quickly offered to drag the stretch trailers in, turn them around and stretch them out, if I got the 1st load out. There was one old (brought out of retirement) company driver there also. The O/Ops said "you may be 1st out, but you'll be last in"! The old guy said quietly, "We used to move super loads with a 6-71". Yeah, I was 1st out and 1st delivered, but everybody heard me coming! I have a Dart oilfield truck from the early 50's. I had a 200 hp 2 valve 6-71. It had a 66,000 GVW (most road tractors have 52,000) and hauled much more as a CGVW. That said, you can not climb Butte grade in low gear at 5-7 mph like I did back in the day,, with O/D O/W loads, you'll get hit a dozen times before you reach the top. I used to almost get hit coming down that grade with the jake on full at the recommended 25 MPH. Drivers both "professional and John Q Public" are not paying attention, and anything that causes them to look up or god forbid, disengage C/C might get you shot at or hit. When I retired, my trucks had around 425-440 hp and were deep into the "Fleet" hp ratings of the day. I moved the same freight, and got it where it needed to go in a timely fashion. I did it the old way, by keeping the left door closed. I ran most times around 65 mph. Tires and fuel went much further, brakes lasted and I had time to react when stupidity happened in the front window.

More or less comes down to: do you slide the reverse idler gear (separate fork) or do you slide the main shaft gear one way for lo, the other to engage with the reverse idler (same fork). Two way to get the same result. The F51 in my IHC is sliding gear for low/rev. They did make some two speed reverse gear trans, now it gets complicated. Mine is sliding gear for low/rev and constant mesh (but no syncro's) for 2nd-5th. Shifter throw is much greater on the rev/lo gate than the rest.

To make thing less clear, some transmissions use sliding mesh on the lowest gear and constant mesh on the rest. Makes it easy to use 1st gear on the mainshaft for reverse as well, most often straight cut gear. The main advantage other than wear (you are going to get wear somewhere, constant mesh just move the wear to the dog clutch) is it makes the trans easier to shift, you are moving less mass.

1st an most likely is a bad connection. If the ground side goes to the frame, and the the engine is connected to the frame with a braided strap, it adds connections and likely fail points, The starter is the highest amp draw on the battery, so run is few connections between it and the battery as possible. Make sure all connections are clean and tight. On my old six volt stuff I run the ground right to the starter mounting bolt, or a bolt on the engine or transmission that is at least 3/8" and make sure the metal around the bolt is clean. I then replace any braided straps between the engine and frame to make sure the engine is bonded to the frame and the same with the cab/chassie. I don't know your engine, so am going to give general advice which may or may not apply: if the starter has a remote solenoid switch make sure it is conducting when activated. A bad ground to the cab thought the mounting bolts, or a bad ground of the cab to the engine both can cause failure. If the starter is operated by a mechanical link and "button" on the floor, the contacts in the mechanical switch on the starter could be at fault. The starter itself could need some attention, Starters of this vintage often had "oil cups" at the rear and sometimes front end. Many times the starter motor shaft ride directly in the cast iron cover and the oil wick is all the keeps it from galling on the shaft. My manual calls for them to be lubed every 500- 1000 miles! Most never see any attention. The starter could have internal problems, like a open segment on the commutator or one bad winding on the armature. If you suspect the starter, pull it out and connect up to a battery with jumper cables, it should kick and spin (just do a quick test, don't run for a long time with no load). Because the truck cranked over on a new battery but then doesn't, could also be something like a stuck generator cut-out drawing the new battery down when the engine isn't running. Check for sparks when you connect the battery leads, there shouldn't be any, with everything turned off (headlights etc). A test light, or volt meter can be of help to check for voltage drop across connections. A quick way to find poor connections on the starter (if it will crank at all) is heat, feel the connections after the starter has cranked (you did say it would crank with a fresh battery) and any warm or hot connection is a bad one.

What Terry said, and blow out the bolt holes when your done with the tap.