Vladislav

The cab lift system contains a pump which is mounted on the RH muffler bracket. It's hydraulic. Operates like a common bottle jack. You use a rod to pump and turn a latch to release pressure when lowering the cab down. When you pump the latch must be in the close position (don't remember, probably clockwise). If no action could be shortage of oil (too probably after a long storage). The filler plug is already on the pump and you can use ATF and even used to get the system operational. There's no catch. Cab locks are hydraulic and mounted below the cab airbags. When you start pumping the jack first makes the locks get loose and after that oil goes to the lift cylinders. Locks could be stuck (in theory) but you will see that if the cab tries to go up and locked near airbags. There's a security support plank on the right frame rail at the front below the cab, use it when the cab is raised. The brake pedal gets seized in the aluminium base. There's a steel piston inside a cylinder bored in the pedal base which pushes the threaddle valve when you push the pedal. You need to remove the base from the threaddle valve and get the piston (actually a tappet) free. Hitting, heating, WD40 penetration are the ways to go. After it's loose sand off all oxidation from it and the cylinder surface and apply grease. The base and the tappet are NOT interchangable with R-model (RW, RD, DM etc) but unique to MH. And too probably not easy to find. The threadle valve is a standart brake valve, same as in R. The big pedal base with MACK script has tendency to corrode due to moisture in the floor mat. A difficult to find part either. Also a weak point of MH is the gear shifter assembly. Could be found broken down or worn out. Front air tanks could be found rotten through where the aluminium steps are attached to them. Windshields and front grill are difficult to find parts. Good luck on bringing her back to life. Vlad

Thank you for the credit My current option is using a pair of rails my second R holds on. Those are stampless and exactly the size I need. But they aren't really nice at the rear end, have some cracks over the Neway brackets. Good thing the cracks are in the web not in the flanges so I hope I would weld them up with no issues in the future. Another matter is I'm way from being excited parting out my only complete and running truck. I will do if no other option is found to the moment. But I also figured I need some other big jobs done such as the engine and two big chassis crossmembers. Also the cab interior and wiring are on the list. So now the plan is to provide as many of works as I can aside of the frame rail story. And when 90% of the components are ready I'd part out the truck to get the rails off, fix/blast/paint them and start assembling everything back together. A trouble to find such rails is they're quite long for an avarage R-model. 220" wheelbase and 60" Canadian spread. From what I figured out there were not many American R-model highway tractors with sleepers and such long wheelbase as a follow.

Looks like they are. And the rear ones also. I was wondering the cab mounts position but after you investigated the rail goes down there that's not a problem either. The problem could be the rears since mines are Neway and the lever brackets fit to the rails by the lower flange. I suppose RD's with Neway are a seldom view if any but that story must have working solution in RW700.

I'm not in the same ballpark but in the same kind of since I'm overseas. For PAI needs I started asking local truck part dealers and found out multiple places which had PAI relationships and straight supplys with reasonable prices, at least cheaper if i order in the States in a on-line store and organize the shipping myself. The only issue the guys are lazy identifying parts so I have to give them particular PAI numbers.

Upps... That's what has me scratching my head. And seems like it has a tendency to spread like infection. My R688 is 1988 and has both front and rear brackets similar to both of your trucks. The axle is FAW537, 12000# if I'm not wrong. # taper leaf front springs and rear brackets cast of aluminium. The pics are what my RD690 donor truck had. Difficult to figure all original specialities since the truck was modifyed by installing of a front drive axle and the rears put almost below the main rails as a section of a DM (judging by the rail heigth) chassis. As you can see the rear brackets were generally similar to R-model style but slightly different and cast iron. The front ones were completey another story. The hood attachment was also another but that makes sence since it was for a newer style square hood. Now seems it worth to me to measure the heigth of the frame rails at the front and relate to your figures. So far I expect the same range figures but it's a guess. The rails are separated and stacked aside a barn. So very easy for observations. You're right. Those RD rails are absolutely decent. That was a double frame and the truck spent the most of its life at extreme North with about no public road driving being an oilfield equipment carrier. So no salt and probably not much driving at all. But the VIN stamping doesn't suit my needs and the front spring bracket differences adds salt to the dish.

Jim, isn't CMCAC a Chassis Mounted aftercooler? I always thought that and expected that attached onto the chassis in front of radiator.

Very exciting Good luck on a smooth job!

Lengthened R-model hood is described like starting from 1982. Does this mean that CMCAC took place starting from that time either?

Very appreciated. Please also check the bogie stand position.

Like this? More looks like it was a winterfront conteining two bars.

This one was attached straight onto the aftercooler. So I expect it appeared together with it. Starting from 1984 I guess. The models are usually 688 and could also be 690.

One more of the kind in my 'puter. Hope none of those watermark holders will have a fan switched on.

You should look for a local PAI/Excel dealer and supply them with the above numbers. Looks like PAI official web-site is Reliable Industries. But I'm not sure they sell straight. Vlad

Couldn't that be a R-model with butterfly hood? Mack chassis (frame) brochure indicates RD (taller) frame railf for an R-model firetruck

Depending on a way you count it. RM has similar to DMM chassis rails, front axle setup and transfer case. So actually all the powerplant and the chassis. Only the cab was used off a R-model and I suppose it was fitted on its own RM mounting brackets.

Looks like there were DMM's with butterfly hood and even non-front driven.

Wow! Keith, many thanks for the pictures and explanations. Actually I had both R and RD chassis but the RD one was partly dismanteled so I couldn't relate everything between them. Also I didn't pay enough of attention to the matter at the time and later we parted out the RD chassis completely so now it's late to. The gap between the lower rail edge and the rear spring bracket is something new to me. For some reason I thought the bracket supports the rail by its bottom. Also my RD chassis had different rear brackets cast of iron (it was RD690 of 1990 or so with a square hood) and my R688 has them alu and of a shape you represented on the photos. Big difference concerned front front spring brackets which were almost different from R688 having big tow eyes in the lower part, almost below the rear edge of the frame rail. I saw brackets which looked similar but used on early R-model chassis. But it was difficult to judge from the pics since those early trucks could also be RD. BTW what was the year a RD model came into production? Were they of 60's and 70's years or started in 80's ? Ok, now it seems mostly clear of the way of installing taller frame rails at the front. Just wonder what was at the rear? Did the bogie stand (if Camelback) just got an upper position between the rails? I think if the spring packs don't meet the rail sides no matter how low rails take place between the springs. Worth to point out my actual matter of interest is a search for a pair of good rails for my R-model. The existing set is almost unusable due to an accident in the past. I looked for solution purchasing new rail sections from PG Adams but wasn't satisfied with match of bend radius between the web and flanges. And also I hate to have a weld seam right in the middle of the chassis or large inserts inside the rails. I said I had a set of really nice RD rails which are tall and really thick. But that game with front spring brackets would put me off the originality again. And there's a point aside of that. My original rails don't have a chassis number stamping. And that is marked in the paperwork. So what I need is clean rails. Deleting such stamping in my country is a crime. That follows to complete regestry cancellation if found.

Yup. There must be a different kind of metal. What a missfortune !!!

Interesting approach. Can't wait progress pictures of a stage when the hood start getting metal not wooden

Excellent entertainment! I'm glad both of you got a blast of emotions which is so needed during the current times.

Unfortunately (or fortunately) I haven't got myself into Valueliners. I really like the look of later RS/RL700 but currently just impossible to cover them up with complex attention. Now I'm really deep in my Eastern R600 and quite enjoy the entertainment which takes plenty of efforts. I think you're right on accomodating the CMCAC by moving the rad and modifying the hood. If you change the front end of a hood you could get more space for an aftercooler, reorganize the hinge setup and keep the look at the same time. As I noted from RS600 chassis pics with hoods removed (mostly posted by you) early and later models had front spring brackets and front engine mount crossmember almost different. So it just a different design with plenty of possibilities to install additional equipment. Investigating my R-model chassis and also relating it to the MH one I noted that vertical (rail mounted) Neway lever brackets were attached to the frame rails with a spicer plate of nearly 3/8" thick on the R and with no plate on MH. Seems like those plates were used to compensate a possible thickness of the 2nd rail if the frame is double. you could also see such spicers where bogie torque rods meet the rails. There's a mounting bracket the rod end attaches to. And you can see such bracket fit on a spicer plate or just straight onto the rail. When you start figuring the way of possible use of the 2nd rails it turns out they could be installed inside with the main rails keeping their original distance between each other but in other cases it appears that when you put the inner rails onto crossmember's ends they would determine the position of the outer rails wider than they woukld be used as a single setup. And that means that all the outer frame brackets such for fuel tanks, battery boxes and even cab mounts would take different position. Seems really strange but seems they would indeed. A fact of the same matter is a chassis mounting Camelback stand. As you know its upper section consists of two portions of U-channel welded together with a center part. When the stand is in place the U's are inside the frame rails. At the moment I have 3 such stands, both in trucks and removed. One of them has steel stripes of nearly 3/8 thick welded along the upper and lower lines of the side U-channels where holes for mounting to chassis bolts are drilled. The rest 2 dont have them. The matter is the stand with the stripes was ised with single frame rails and the 2 without them were installed in double frames. Again, here it's clean you have spacers in place of possible inner rail and when the rail presents the spicers go off. But the story with airride suspension looks like the distance between the main rails may vary. And thats strange. Also a miistery (I try to be short) is chassis differences between R600 and RD600 frames. They have different rail heigth (the same is between RW600 and RW700) What does that mean? That means that the rail lower edge seats on the front spring brackets . The cab mounts are attached to the rear ones of those. If so the upper edge of the rail must be closer to the cab floor than with narrower rails. But in fact it looks like it doesn't. This means that the sizes are compensated somewhere. That could be done by different brackets which difference you can't see by their look, or by higth of the front axle springs or by any other way. Actually if you just drive your truck you don't mind such matters. If you restore an only and complete truck that also doesn't bother you. But when you start investigating ways of modifying or possibilities of use parts from one chassis on another a very patient attention is required to avoid unpleasurant missmatches.

Don't worry much about that. If you get to snow you would compensate the shortage of feelings very soon Brrr...

My suppose it was done by a different way. If you move front hood attachments you've got the front axle line backwards relating to the wheel arch. Could be done since 1 inch isn't really notable but I myself never noted such offset. In fact moving the hood hinges or cab position is provided by modifying (or moving) mounting brackets. And when you start investigating their design it turns out Mack used different styles of them during the years. Front ones where the hood hinges fit were made as different shape castings on early and newer R's (I tell now about Eastern R600's ) And later RD's starting at least from 1989 got front spring front brackets looking the way the early R's had but I don't know they're similar or not (but suppose they are). Cab front mounts are (as long as I could see) the same on early and later R600's. But front spring rear brackets (the cab mounts are partly bolted onto them) changed their style at some point. So cab could seat different. Worth to take that bolt holes in the frame rail determine the cab bracket position so if they're drilled the same the cab should have constant position. But was the rail drill pattern changed between early and later R's or not is a matter I'm not familiar with. If of real interest the way is requesting Mack Museum for the frame drills layout. If I resolve to modify my frame design with different brackets (I honestly thought about such entertainment for a case of using taller RD600 frame rails for my basic chassis R688) I would bother the museum. But for modelbiulding seems enough to take basic sizes off a production brochure or someone's real truck. All in all there's plenty of points in a Mack chassis which look simple at the first moment but when you start figuring it turns out many sized and distances differ between the models and production years. In many cases that's not really much but require clearing if you want to provide a correct work.

Mack added 1 inch to the rear edge of R600 hood to accomodate the chassis mounted aftercooler. You can see the difference if look at a hood side behind the rear of fender. After 1982 there's a section of fiberglass prolonging the hood side rearwards to the cab cowl. And pre-82 (shorter hood) doesn't have it and ends right along the fender curve. Once i asked a question on here and got an answer of pre-82 hood length (total?) was 53-3/8" and after 82 it became 54-1/4"

Pretty nice! Looks like a perfect environment for off-road travels. Here we have it very popular also and plenty places to go. But usually you have a choice of swamp/clay or snow. Snow is preferrable in many cases since less dirty