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Macktruckman

Eaton behind maxidyne

Question

I have a 1978 R685ST with a 285 maxidyne and the 2 stick 6 speed with 4.17 rears and tall 24.5’s. Truck is getting a new cab this week and paint job. Old cab is rusted out badly. I have an Eaton RTO14909MLL from a wrecked mixer truck with E7, I think has mounts that will work. Now would be the time to swap transmissions if I want. I was thinking it would help lower my rpm at highway speed and give me a little more top end and maybe help me out on hills. I live in an area with lots of hills. Pull a lowboy to move my equipment and pull an end dump. I like the 2 stick but the gap from 4 to 5 is pretty big with all the hills and I can only get about 60 mph or so on flat ground to the floor tached out. Transmissions look to be within 1”-2” of each other in length. U joints different. Would it be worthwhile to swap? Since the cab is off anyway 

thank you 

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There’s a few pictures of the rust bucket. Thanks to rob for help with loading pics. 

Got everything apart and started back together today. I went ahead and pulled the 107 and put the 9LL in with a new ceramic clutch kit today. Got the new to me cab and the hood painted with DuPont imron. 

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Maybe me stupid, but skip a gear let the engine think you still got 6 gears till you get to the top and then move on. not like you have to use every gear, and your mack is not going to over power that 9, but then after starting with a B model 673, with turbo and triplex  and hundreds of trucks later maybe me still don't know nothing,  I remember alot of 300 hundreds that ran out of arookstook county with 13 speeds behind them and they did fine, not 300+  good old 300s  and Aroostook county is in Maine (in case you didn't know), where it gets cold and little trucks hauled big loads.

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I figure it’s like everything else. I’ll learn how to shift it and where it likes to be shifted after a day or two. I may take robs advice and pull the pump and injectors and have them reworked too a little later on. I figured that is easy enough done anytime. Right now was kinda the time to swap the transmission. And having the cab off, I just lifted it right out the top. And it’s probably a good thing I pulled the old one. The clutch was pretty worn. I didn’t really want to buy a clutch yesterday but I would have been much more sore if I didn’t and it went out in a couple months, you know?

 

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And I rode with my dad in a b that had a quad I believe. By the time I was old enough to start driving any that old b was demolished. I’ve never driven one with a triplex or quad. 

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I was suspicious of that cooler being non original because I was under the impression that the 285 originally had only air to air, no water. That’s why I sent that particular pic to you. Thank you for mentioning it. The id plate was gone off the block when I got it but according to the casting it shows to be a 285?  It was indeed a oil field tractor. Guy I bought it from said it had spent some years pulling saltwater. I attributed the severity of the rust to that fact. Could be wrong though. I would like to give it a touch more fuel. I’m not interested in killing the engine but maybe a touch. It doesn’t really put out a lot of smoke. Might wait though until I see how the transmission makes it act. 

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And we have another truck that’s almost identical to this one but that truck is an 81 (could be 82)

its got the front cooler and tag says it’s a 300

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I’ll see what is stamped there in the morning when I get to the shop. I’m thinking that’s where I found the number that made me say it was a 285. But it’s been a few years now so I’ll look there in the morning. The guy I got it from advertised it to be a 300+, but I just figured it was a sales pitch and didn’t give it a second thought. I always assumed because of the majority of trucks about this year we had around here were 285’s, this one is as well. But I’m no expert and I’m just now starting to learn some of the variations. 

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Still working on my old r. Little by little it’s going back together. I’m going to put dual exhaust stacks on it. I have everything I need to do it I believe. I converted my cab to air ride so I don’t wanna bolt brackets to the cab. I have some angle iron and some rectangular tubing I was thinking of fabbing up some stands and brackets. But I got to thinking it has an aluminum headache rack going on, can I bracket stacks to the headache rack? Not have to fab up nearly so much? Looking for suggestions from you guys that have been there done that, maybe with some pictures. Thank you 

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I don't see why you can't attach the stacks to the headache rack, seems like a good idea to me!

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That's cleaning up nicely!

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Thank you, its taken far longer than I anticipated but I’ve done a whole lot more to it than I planned. I got 4 aluminum wheels for the rear but I’m having no luck finding wide aluminum front budd stud pilot. I want a pair to match the rear but new ones I’m finding are $550 each. I’d sure like to buy some used ones

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I like the black rims on the steer. Look like cop wheels! That's one sharp looking truck, you're gonna get some eyeballers when that hits the road!

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On my 1985 the stack is connected to the cab and the truck is a factory air ride cab according to the build sheet

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I clamped mine to the headache rack. Hard to see in the picture though.l sold the truck or I would take a better picture.

image.jpeg

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I got one side on today before I had to go do other things. Should get the other side tomorrow. I’m just fabbing some brackets that I bolted through the headache rack and then used peterbilt clamps and isolators to fasten to the brackets. 

Thats an awfully nice truck there. 

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I’ve never had a headache rack on it. When I first sat the rack on this morning I almost abandoned that plan, I didn’t like the way it looked at all. Just all big and out of proportion. But it’s been sitting in the weeds and needs some cleaning and elbow grease and it will probably help. The biggest help was when the stack went on then it all started to look a little better. Not so huge looking then

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I thought the same thing when I put that one on. It was taking up room in the garage so I put it on and once I got the stacks on it wasn't to bad. I've only seen the truck once since I sold it and he put aluminum wheels on the rear. I hear he stretched it out now. I know he wanted to put a big bunk on it.

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Sure looked like a pretty truck

theres very few old Mack’s around here anymore and none are slick. Mine definitely won’t be perfect. Far from it. But it’s leaps and bounds better than it was. There are some ch’s around, but they just aren’t the same 

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