SpreadingLime

Full set of spoke wheels and radiator shutter looks intact.

Ok folks here it is. I found this ol girl in a field sometime ago. I bought it and had it towed home. I don't need it but I couldn't let it go to scrap. She's pretty rough but I wanted to give everyone a chance for a part or two. The cab is pretty straight, needs floor pans. It has a tip turbine engine that doesn't run, and a five speed. Gauges all are there. Shoot me a message if there's something you might be interested in. Thanks ,Cole.

Cool. I'll give it a look.

Vlad, your insight makes sense. I'm not starting a project or anything. It was just one of those times when you go " I wonder..." Now I know why its not a common modification. As always good talking to everyone. Have a good weekend.

Jones doesn't offer a R700 hood. At least I can't find one on the website. I recently read a post here about a CL that had been converted to a set forward axle. Then they had to "stretch" a CH hood to complete the conversion. That got me to thinking. Mech, I think you're on the right track. Splicing two hoods would be a better option.

I hope this topic hasn't been beaten to death. Have any of you ever had a R600 hood lengthened to R700 specs? Is there anyone who does it professionally? I suspect that any reputable fiberglass shop could do the job, but someone who did custom semi work might understand the idea a bit more. Thanks to all.

Maybe the gauge was upside down? Just having a bit of fun. In all seriousness, I've been there too. It's painful, embarrassing and expensive. Hope everyone is ok.

Thanks all of you for the info. The history that all of you have stored away is always impressive. "Mech" you are correct on the truck being a 685ST. Build sheet from Mack says that the rears are 38K. I kind of suspected that the round tubes were just an older design like Terry had stated. Everyone have a good weekend.

Hello all. I've recently acquired a '75 R685 for a parts truck/ fixer upper ( not sure yet ). As the title says the rear diff housings have round axle tubes instead of the square that I am used to. The carriers are Cr 92 & 93 , same as my other rigs. My question is are there any differences in round vs square housings. Are they just an old design? Thanks all.

That one will be the envy of all the wrecker guys in your area. Even if they won't admit.

Here she is. Ole reliable.

Not much anhydrous is used around here. That's flat land stuff. Ammonium Nitrate is all that available around here. Along with DAP and Potash it's the cheapest of the three, but still too expensive.

My typical day

The spreaders are New Leader 3020. They have step up motors that turn the fans. This keeps them turning at the same RPM no matter the trucks speed. Theoretically. 1500 RPM on the motor is where I typically run. This gets me 7ish MPH field speed and the beds seem to perform well at that RPM. And yes I've seen my camelbacks for some impressive stuff. My 88 has a 38k and the 93 has a 44k. Honestly the 38K gets better traction and holds the terrain better.

Morning guys. Sorry for the slow response. It's been a week. All of the info is greatly appreciated. 1. Joe, thank you for especially for the tid but on the lifters. If I decide to run these motors I'll have extra on hand. As to the torque arm, I have a second RD690 truck for parts. I have plans to use the front and rear suspension from it and put under the '75. I know it has a torque arm. 2. Bob, I like your way of thinking. I don't mind repairs but I would hate to put a Chinese "anything" in one of mine. 3. Too all. I make my living spreading commercial fertilizer and Ag lime in N Arkansas. 300,000ish miles on the '93 truck. Unsure of the others. 48k to 50k total weight is pretty normal for me. Lots of rough, steep ground to drive over .

Thank you. That's good to know.

Hello all. Here's my question. Do you feel that the 675/676 engines can be kept running for say, another 10 yrs? I ask because I am a small business owner and I run R models daily. My go to is a 93 RD690 and my backup is an 88 R690. Both 300 HP and seven speeds. I have recently acquired two more R models for parts. One is a 60s R600 and the other is a 75 R685ST (I think). They both have tip turbine engines. The 75 looks to be a 237 that has had the aftercooler added on. The engine tag reads 675 and the hood has been cut to allow for the second breather tube. Both have cabs that are in decent shape , which is why I bought them. I know these old Macks are dead reliable , but they all need repair at some point. I am concerned with availability of parts (mostly engine). Is it a good idea to try and restore one of these with the intent to put it onthe road in 2023? Would a swap to a newer engine family be advised? Thanks to all.

Hello again. I am curious about different styles of shifter knobs for the 2070 and 2080 transmissions. Is the Black plastic shifter with the Blue up/down range selector the only style that Mack offered. I am looking for something with a more vintage look. This is probably one of those new guy questions that all of you have answered a hundred times, so I apologize. I tried searching the forum and aftermarket sites and didnt come up with anything. Thanks.

Are you still buying engines?

I have a 7 speed 2070A I would part with. Where are you located?

Ok. Good to know. Thank you.

Hello all. I wanted to know if anyone has changed hoods on a RD690 from the newer square style to the classic R model hood style. I currently have a 1993 RD690 (White) and a 1990 RD690 (Blue). The 1990 is a parts truck. All the hood components are there. I have looked and it seems possible. Just curious if anyone had tried.

I have seen that chart before. You're explanation makes it much clearer. The text at the bottom of the chart refers to a "1750 RPM Engine". My headliner has a sticker that says "Working range 2100 to 1200 RPM. This makes me think that I have a Ecodyne engine. As I understand the Ecodynes worked at a higher RPM range for fuel economy and the Maxidynes worked at the RPM range refered to in the chart, producing the "famous" Mack low RPM pulling power. I understand and agree with the logic of your response , it may be that the numbers are just different for my particular engine (as you mentioned). Thank you.

Hello all. This is my first post on the site, so please bear with me. Im sure this topic had been beat to death. I am the new owner of a 1888 R690, E6300 ( not sure about Eco or Maxidyne) and 2070A. This is the only heavy truck I've ever driven. It has spent most of its life as a spreader truck in North Arkansas. New Leader 3020 GT bed, 38k camel back. This ole truck has HARD life. I am struggling to master shifting. I have read all I can find on the subject, and talked to everyone who will listen. Most says that you come out at 1800 and go in at 1200. That's not working. I've found that out at 2000 and in at 1600 works much better. That's only for upshifting. Downshifting is a whole other animal. It's is very speed sensitive. Just to go from 7 to 6 it must be around 37 to 34 mph. Any faster, forget it. 6 to 5 works best at about 24. Forgot to mention that there is no Jake brake. This results in using the foot brakes ALOT! I'm starting to think that the transmission is just worn out. Also do Maxidyne and Ecodynes have different shift points? Any help is appreciated. Thanks in advance.