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My first R Model


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Bought a 79 RS600 today. My first R Model, in fact; its my First Mack. I have driven R models a bit in the past and have always liked them. I have the E?300 in mine, its a 1983 Model engine and he 12 speed transmission. There are no tags or shift pattern stickers inside saying which tranny it is but im assuming its a 12. 5 main gears with a Direct and OD and R on the air knob and the "bull low" stick next to the seat. I can shift it alright but I think Im missing something,...im still grinding more then I think is normal. What is the proper protocol for shifting these things? When you upshift from direct to high, do you simply move the selector knob towards H as you get off the throttle? Do you clutch and get off the throttle? And downshifting, do you move the selector and throttle up to match revs or clutch and throttle? And upshifting the main gears, do you preselect D as you prepare to upshift to the next gear???

Any info would be great.

Thanks

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Hey hey full floater welcome aboard now you have an R model it will feel like your floating in heaven

how I shift is keep the power on flick it to high or low depends on what your doing going up just on and off noise pedal as long as you let it drop 400 rpm or there abouts it shifts straight in going down same procedure on and off just make sure the revs increase by at least 400 rpm

if you cant get up a hill by splitting only then split the gear other wise drop a full gear drop

if your only lite in weight 80,000 lbs or so just drive it like a 5 speed maybe split 4 and 5 heavier weights might have to split 3,4 and 5

your living the dream now R model with a 12 speed paradise only way it could get any better is if it had a Jake instead of Dynatard

seeya mate

Paul

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Not sure if other guys would agree, but the mack gearbox seems noisier than a roadranger, so a noisy gear change isn't a problem. Maybe that's lack of insulation in the cab?

Also, mine seems pretty happy changing up or down with no clutch. Ya just have to get used to driving it. Every truck is different.

Enjoy your new toy.

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Thanks so much for the positive feedback, im very happy with it thus far, only 225km on it. I will practice the shifting more and more in hopes to get it mastered.

Ok, that makes sense to me mrsmackpaul. But just to clarify, if I want to shift from H to direct; I would maintain my throttle input, preselect the "D" and then increase the throttle input by the 400 revs to match that gear and it should go in? Is it normal and typical for them to growl and grind just a bit when splitting? I have yet to get a perfect no growl shift, but im getting close. And yes, mine is very whiney in 5th over, much louder then a fuller trans no doubt.

What fluid to these trannies like? And how about the 300 hp Mack engine? Are they a reliable engine? Any maintenance tips or things I should look out for? It seems to really like being around 15-1600 rpm. Do you guys run a lube additive in your fuel? Mine runs at around 160 degrees and climbs to about 180 on hills and about 200 if loaded with some weight. I have not maxed it out yet for weight.. Is that about the right temps?

Mine is a water truck, 4000 gallon with a PTO pump (which has a broken driveshaft at the moment) I'll get pics up this week.

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when you go split the gears just flick switch on the knob and on and off the go pedal and bring it up to the correct revs

300 Mack I would think should be as tough as any other Mack motor of the time they will pull like a freight train lug right down to 1100 rpm fine

Paul

these fellas on here will be waiting for photo's

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Yeah im going to work it. Forest fire fighting in summer months. Its actually pretty clean for a Canadian truck, next to nothing for rust. So im going to paint er up a little better, newer tires and rims. I have 23'' tube type rims on it now. What are my options for a newer steel rim? Does Mack use any special bolt pattern or anything I should know about?

Thanks

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Leave the spokes. Changes can be done with large hand tools and you are back in business.

Not familiar with a 23" tube type rims? Maybe you have 24"?

There is no tubeless available for 24" but there are tubeless options for a 20" or 22" spoke.

Jim

It doesn't cost anything to pay attention.

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Every tire shop i talk to, recommended getting away from the spoke tube wheels. But they also could be just trying to sell me more parts and labour also. So i thought i would do some more research. If i got rid of the spokes, i guess i would need different hubs to wouldn't I?

Yeah the rims measure to be 23-1/2". Would that make them a 24?

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Welcome aboard , nice RS !!

Just take a look at the tire size on the side of the tire. Let us know the actual size. Someone will be able to tell you the tubeless equivalent .

I think it's a good idea to get rid of the tube type. They can be dangerous if your are not familiar with them. Its hard now to even find a tire shop that will work on them.

Plus common tubeless are way cheaper. You just need rims. You can get them cheap from a wrecking yard.

KEEP THE SPOKES THOUGH.

Keith

Keith 

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Thanks guys. The tires say "10-20" on them. So just to clarify, i can toss a timeless tire and rims on my existing hubs? And just keep the spoke wheels for the sake of it (which is fine by me) or are you saying keep them in the truck?

Sorry, its all new to me....

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The engine is more than likely a E-6 300 which IMO are one of the best engines Mack has ever made, I learned to drive on my dads 82' rd 686 tandem dump at 14 yrs old that had the duplex 5 speed and the E-6 300 in it. That truck would run and was very reliable, it would still be on the road if it wasn't for the frame rusting around the rear end and my dad decided to get rid of it and get the 01 instead of fixing it. The older Mack transmissions take some time getting use to , they will separate the men from the boys. Good luck with your adventures and I hope you enjoy your new to you truck.

Tony

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And if I went away from the Dayton style rims and got some budd rims and hubs, would the hubs needs to be Mack specific?

You could get some Meritor hubs. You would have to determine which bearings, seals, etc. you need to match between the new hubs and the front spindles and rear axle stubs. You will also need different brake drums to fit the budd hubs. Plus miscellaneous parts for the conversion.

It can be done. $$$ will be spent.

Jim

It doesn't cost anything to pay attention.

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Found a running parts truck with a 300+ and budd rims and hubs on the drive axles. I have not looked at it in person yet but im looking tomorrow. Im assuming they are Mack diffs. That would be a good score to find the hubs, drums and rims in one shot. They are also 22.5s. Is there anything i should look for in regards to compatibility of axles to accept those hubs? I'd like to swap the hubs, rims and drums or whatever i need to, onto the tank truck.

Also, i picked up everything i need to paint the tank up, so that's exciting!!

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