Art_H

My '77 12 speed tranny is supposed to take 80w90 gear oil acording to the TS442 service manuals. However the common practice at the local Mack dealership is to use 85w140 gear oil. Comments or thoughts? Thanks

had alook this morn... turned out to be a leaking #6 exhaust manifold. Just a slight leak until the pressure climbed up. The valve cover gasket that leaks a little masked the telltale soot indicators. By the way, it seems difficult to seal these valve covers. New gasket and it still leaks. Heard you just have to get it on the 'sweet spot.' Thanks again.

What about an injector having an issue and opening at lower pressure etc? Would that not cause black exhaust?

Mack 300+ ETAZB673A on A RS600L '77. Just experienced an upper RPM 1600-2000 exhaust fluttering noise when into the pedal. The exhaust is also black where it is normally clear when in that RPM band when loaded. Otherwise idles great and no other symptoms. Seems to also be intermittant. Is this the symtom of a fuel filter just getting plugged at higher fuel flow?? Injector pump getting starved? bad Injector? valvetrain issue? Thanks.

Just gearing up to replace my RS600's trunnion bushings. I want to replace the camelback spring center bolt. That is the rod that runs down the center of all the leaf springs. Mine are currently not too healthy, and I woul likely have to cut them off. Any ideas on where to get one? Just use ready rod Gr8? From what I have gathered, they have a stud at the end and it feds through the upper trunnion block? Thanks, Art

No spring change required? Just the 1 piece bushing is pressed onto the trunnion? That piece replaces the 2 piece clamshell system? Thanks. Art

Old thread I know...But I'm replacing y worn rubber trunnions to urethane. My thoughts are that the grease would help the urethane move on the trunnion shaft. I understand the theory behind protecting the rubber style from harm, but clearly the urethane is impervious grease. Thoughts?? I did manage to snag some 30wt non-detergent oil...but I don't tyhink I'll use that now. My Mack TS442 books spec 'edible mutton tallow or 20 Wt non-detergent'. ' Glad I saw this thread before I started torqing the u-bolts... Thanks, Artt

With urethane bushings is it really neccessary to use 'edible mutton tallow' or 20 wt non-detergent oil?? I suspect that spec was to preserve the rubber bushing. With an inert urethane bushing, why not use ep2 grease?? Further, why not drill and tap for a grease nipple? Thoughts?

thanks mate

Just looking at what size axle nut to get for my Mack. 38k axles camaleback. I suspect that it's a 4"?? but some of the part numbers I have found say that they are 4-1/8"?? Anyone know??T Thanks

RS600L 1977 38k Camel Back, and I have the s-cam inboard drums. ( hub and drum all one piece ) So I'm looing to see if I can change the hub and use outboard drums??? Any ideas? Thanks, Art

Yeah park brakes on both axles. Does your Rear drive wear more than the front drive? I can see how Mack would maybe say that, but with new (replaced) air brake parts since 1977, I don't buy it. The system is too simple. There are factors like air hose routing and fittings that can get in the way of equal axle air pressures. But a 50% difference in heat on the drums is a lilttel too much for me. It means my rear axle would lock up early trying to stop the whole truck. Maybe if I tighten the slacks a notch on the front drive axle, it will equalize. On another note, these IR heat guns are a great tool when troubleshooting. Thanks for all the replies.

All good advice. I was thinking that this may be a common issue. But maybe not. I had a quick look with an IR heat gun, after a good hwy stop. I got the readings from the drum lips exposed on the inside of the wheels, to get accurate temps. Rear drives were about double the temp than the front drives. Rear drive around 50 deg C (120 F) Front drive around 25 deg C (77 F) Thanks, will have a look to see if there are multi relay valves. The good lining on front may have been possible, but now with the temps, the rear is clearly doing the lions share of the work. Slacks are all good just changed manuals all set. Truck had been serviced exclusively by a Mack dealership, and they didn't pick up that in 8 years they have only serviced the rear drive brakes...twice. lol

1977 Mack RS600L 38k bogie with s-cam on the drives, seems to wear brakes more on the rear drive, than the front drive. Just bought the truck a few months ago, and I have the service history from a Mack dealer. The guy really looked after the truck. But I did notice that there was never any history of front drive brake work in 8 years, and 80k miles. Any ideas as to why?? I'm going to try and track down the previous gov inspection sheets to see what the linings etc were every 6 months. I have the inboard drums as well.

That sounds reassuring. A lot of the front axles available used seem to have the steering box as well. Is the steering box required for that particular axle and steering arms etc?