Kav

Paul, I agree with you about the Dynatard being unimpressive. Even if you get them operating perfectly as Swishy said, they are only about two thirds as effective as the Jacobs in the two valve motors which is all that I have. The other disadvantage with the Dynatard system is that the Rocker shaft wears a lot more than the plain non Dynatard shaft and this oil blows out the Tappet cover Breather. Over the years I have converted three maxidynes from Dynatards to the Jakes and I found it was well worth the trouble. The Jakes in a Mack have never ever been as effective as in a Cummins, so if you are expecting those sort of results you will be disappointed. When Mack in Brisbane brought out the first Econodyne motors they switched to Jakes, so they must have seen the advantage in them. I have heard of a system where a mechanical exhaust brake was fitted in conjunction with a Dynatard or Jakes and this was very effective, but I have not actually seen it. Just a few ideas, Paul. Kav

I checked the Cabs here and four of them had the line down the panel near the grab rail and the fifth, the 1976 Model is just a flat panel without a crease line. It was one of the first Models fitted with the deep Cab in Australia, so it could have been from a different supplier in the USA or a different order. They all have the long Grab-Rail. Cheers - Kav.

Hi everybody, In the early 1980's we upgraded an R Model Cab from the short back to the long back and fitted the air bag to the back and the trunnion mounts under the front. This also involved remounting the bonnet hinges from the Radiator mounts to a direct Chassis mount and rollers were mounted on the front of the firewall to allow the cab to move in relation to the bonnet. The original tank mounting crossmembers were 2 inch square, which apparently went back to the B models. In the conversion to the Air suspension Cab the crossmember was changed to a 3inch high by 2inch RHS. If you hit a really big bump, the bottom corners could hit this crossmember, so a rubber buffer was fitted beside the air bag to limit this. The cutout in the Fibreglass cab gave plenty of clearance to stop this happening. To modify the cab for the deep back you needed a new roof and headlining, a new outer back panel and a new inner back panel and lining, possibly a new rear glass and the longer grabrails. Back then the Aircon was mounted on the roof so you had to put new reinforcing bars in the roof to support the unit. I still have the truck and use it occasionally. Just some memories. - Kav.

I don't know much about the V8 motors, but the E6 motors will get excessive blowby if the rocker shafts are worn. This applies especially to the Dynatard motors. If you lift the Tappet Covers and start the motor, if the shafts are worn you will see oil spraying out everywhere, and this is what causes a lot to go out the breather tube. Just a thought- Kav

Hi Randy, we worked a 6 speed for 18 years on heavy local work. We did over 600,000 miles (but huge hours) and in that time wore out 2 Maxidyne Motors and is now on its third Motor. We always did the123 then into high, as it was easier to get a smooth change at low speed that way. The truck is still going and still has all its original bearings except the rear output one. It is hard to make the first change from Low to High smoothly without grating, at very low speeds unless you are going down hill on a hard road, so I think that the smoother change far outweighs any other possibilities.-Just my thoughts - Kav.

One of the main reasons that the filters were mounted on the chassis is that when they were attached to the early Maxidyne and C motors, the Mack filters used to crack around the top and burst due to the vibration. Once they were mounted on the Chassis the problem went away - Kav

Hi Jocko, Back in the 1970,s Mack in Australia would not allow a Quadbox on a 237 Maxidyne as they claimed that the Torque was too great for them. They said that the C motor which was 250 HP and lower torque than the Maxidyne was the biggest they would guarantee. They did a great job with the C Motors and would outlast the Motors in many cases, even when pulling road trains. The first Maxidynes which were fitted with the Maxitotque 6 speed Gearboxes had the same top overdrive ratios as the Quad, which was about .6 . These still had the Push Clutch fitted. The early V8's which were fitted with the Quads by Mack were not high torque motors, but you still had to be careful with them. - Kav

Can anyone tell me what the spring loaded plungers inside the Jake adjuster screws on the 675A brake units do? This type of screw is hard to get here. The later adjusters have a different plunger system and I was wondering if they could be used to replace them - Regards - Michael.

Hi Krismoriah, Try putting the front wheels of the truck in a gutter or hole to make it slope down in front while it is running. If the surging stops or changes it usually means that the Weights in the governor have worn bushes or are loose. You can just slip the governor housing off and check it. It is a good idea to change the bearings in the Governor at the same time and fit new gasgets. It dosen't cost much to do this. Regards - Michael.

Hi macattack - Have you checked the Caster on the axle. If the springs are a bit sagged it will change the caster angle and that can give you the wobbles at certain speeds and conditions. When you said that it is still there when the truck is loaded makes me think that it is connected with the angle of the axle. Does it have any wedges between the spring and axle? Just a thought - best regards - Michael.

Hi Bigdogtrucker - The fluid in the Harmonic Balancers can go hard when they get old and the balancer cannot centralise and this can cause a vibration. Over the years I have had to change several of them because of this. Best regards - Michael.

Hi topo - The 673E motors sold in Australia did not have Turbos fitted to them as they did not have Piston coolers fitted as standard equipment. Some turbos were fitted by the owners and they seemed to work well as long as you did not increase the fuel settings, as this caused pistons to melt. Best regards - Michael.

Hi Joe - The gearbox that you need is the original 6 speed which had the overdrive box in front of the main 5speed box. They are a double overdrive the same ratio as the Quad (about .6 overdrive). They brought them out when the Maxidyne engine was first released. Mine used to do about 55mph at 2100. Regards - Michael

Hi SDB - The two valve 350 go up to about 30 psi in a long hard pull. If your fuel is down or you have some air leaks, it will cut it back a lot.Regards - Michael.