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

My one does the ssme thing. Mack told me it was common with the older Macks. Does yours have parking brakes on both axles?

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.

check if truck uses 2 application relay valves, one could be bad or if it uses one relay check hose plumbing if front hoses use 90 fittings and rear don't that could be a issue also check slack adjusters for equal length also check size of chambers on both axles . have you watched the brakes apply? could s cams be installed bassawkards?

if every thing checks out plumb 150psi air gauges onto front and rear axles and note application psi on both axles if this checks out check brake lining maybe damn good lining on frt. axle and soft butter on rear.

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?

I've been meaning to upgrade my front axle wedge brakes to s-cam. Maybe the better option is to do a complete axle swap. Most of the axles I see used, are from newer Macks. What front axles would be compatable for my truck?? I have the hydraulic cylinder steering assist. Would I have to change the steering box as well??

Or is it just easier to find a donor axle and remove the mounting plates to converto to s-cam?

Thanks

I just bought a 600ft lb TQ wrench to be sure for my wheels etc. The front wheel nuts were all over the place 450-550 lbs ish.

The nuts do look as though they are sunk into the wheel taper a little. Maybe I'll get some new wheels when I get new front boots...or get them machined. Maybe the plastic spacer in between the wheel and the hub.

2100 loaded 2300 no load...per Mack's specs

They will turn faster but valve float will become an issue. I don't know exactly where that happens. But suspect around 2700-3000

Our sled puller turns around 2500 and was told to not spin it faster.

Thanks for the info. I've been afraid of taking it past 2000, and it makes hard to shift into the next gear going uphill...

Mack 12Spd 1070. I believe the rear diffs are geared fairly high. 3.??:1 I don't recall exactly, have to look it up.

Just got a hold of by uncles Mack service books, so I'll cruise through them. A little light reading.

I don't normally drive on the highway, just local windy roads with big hills. So I don't want to over rev the engine, but it is difficult to get into the next gear sometimes on a bit of a hill.

It does seem to be a little odd. The prev owner tried all the different methods of installing the wheel studs etc and torqing to spec...maybe they had the wrong spec...lol

What would the tq spec be fpr an 18k fornt axle 10 stud?

Thanks for the brochures. It's nice to see some of the original literature.

So with a peak HP of 1900 for the ETAZ 315HP, what would be the max safe RPM?

For the Maxidyne as an example?

Are the valve springs the RPM limiter??

I just snagged a 1977 R600 with an ETAZB673A, 315+ engine. Thermodyne??

I can't seem to find any info on max safe RPM and power band etc for the 315+ engines. Any ideas?

Also noticed a little oil coming off the bell housing. How much is normal, and when to worry about it, ie fail an inspection??

Thanks

Just looking at getting a 1977 Mack RS600L, with an 18'000 lb front axle. The owner says that he needs to replace the front wheel studs every year. Any reasons for such a short life span?? Is this a common issue??

Seems to have the 315 engine and a 12spd.

Thanks,

Art