Lmackattack

Mack sells a spray can that matches the silver or tan paint used in the R models. I sprayed my vinal dash and inside the cab with it and it is holding up pretty good so far? I had trouble getting interior parts for my R model. I even tried using a a vin number from a 4 year old R model. I thought it may have just been my mack dealer not wanting to help but I did try another dealer and got the same answers?? let me know what you find

just for refrence if you ar looking for a 4.xx ratio. Many R models with the 6 speeds (1.1 direct trans) came with high 3.xx to 4.xx rear ratios a 4.17 rear with direct drive trans will do about 63MPH ish at 2100RPM with 24.5 rubber a 3.87 rear would give do about 68MPH at 2100RPM with 24.5 just some options there for ya.

"gold paint" is just another reason that it is likely a 6 spd

Very cool Barry That would be neat to have even if it was not my truck when new. Hell, I wasent even born yet when both my trucks rolled off the assembly line

Come on larry give it a shot . Its not as hard on the truck as you think! just dont use LOW LOW!!! I see lots of twisted drive shafts with that gear. Missed both of the Truck pulls this year. one because I was out of town the other was 2hrs south of me but I was just to damm tired after working all day to make the trip. Maybee next year?

here are the pics of the internal destruction. its hard to see but the "tear" goes all the way to the turbine blade aera and bypassed most of the snail housing. Enjoy

fixed I pulled the turbo off the manafold and found the intire center separtor wall of the exhaust snail was deteriorated and missing!!. I could clearly see the back of the turbine blades LOL. i think that would explain the issue with low boost . I put the "new used" turbo on and I can now get 15 psi at 1100RPM and a full 25 psi at 1900RPM She pulls like never before and EGT temps are very low at cruise. this was fun but glad its over.. Trent

2nd Update: I did a "sniff" test today. With the truck running I sprayed either around the charge core to see if it was sucking air..i.e leaking. no change in engine speed or sound. I also sprayed it in the tip turbine fan to see if it was leaking on the inside of the core aera. no change in engine sound. I removed the turbine fan to inspect the core. it looks clean but lightly sprayed it down with water to see if any dirt came thru. all looked clean. with the turbine fan removed. I plugged the turbine feed pipe hole with a cap and took the truck around the block to see if I could get more boost. With no boosted air being able to bleed off to through the turbine fan pipe. i was able to get 16 psi of boost when I held my foot on the brake to give the engine a load. EGT temps were obviously rising very fast with out the turbine fan installed, so I only did a few test trials. I still cant hit full boost or close to factory spec boost. It did however make the boost a little faster than with the fan installed so it leads me to belive that there is a large air leak that I have not found or that the turbo is worn out? Im leaning towards the turbo fins are worn out and not allowing it to make factory boost levels? I should have a spare 285 turbo tomorrow to test my thoughts. What do you think? on a side note the check valve on the fan inlet had a rubber flap that was a little worn as well. it was more or less contoured to the metal bridge that regulates how far the flap can open. I will be replacing that flap if its still availible at Mack just to elimanate that as a problem. Thanks for the help guys.

Great pics Don, sorry I missed you heading over Donner pass. I went thru there around 9-10PM, maybee next time? Trent

Update: This week I installed a factory wire lead from the EGT probe in the Exhaust pipe to the EGT guage. Temps are still high under load. I checked the crossover pipe and all the rubber clamps, no signs of boost leaks. I was only getting 14 psi of boost so Today I Replaced all the exhaust manafold gaskets, studs etc... to make shure no exhaust leaks. my boost guage is now reading 15psi on a hard pull and temps are still high. this past winter when I took put the boost guage in I was getting 18 psi but I figure that was from cold temps? I asked my local mack dealer what boost psi I should see and HK you were correct 18-22 depending on the condition/ age of the motor. This motor uses no oil and when I had the manafold off there were only 2 cyls that has a very, very slight trace of oil seaping past from a valve or something. It did not look like a caked mess that some old engines have. all looked normal to me. Im thinking that this low boost is possible cause for the hight EGT. I was thinking about swaping a diffrent 285 turbo on to see if it makes more boost. my turbo has a few hair like cracks in the snal but no exhause leakage from them??? only thing I can think of now is the charge air cooler is leaking? does the air that goes thru the tip turbine make its was back to the intake manafold or does it blow out to the out side air? I cant hear any air escaping?? Thanks for the help Trent

ebay has the round knobs in diffrent colors all the time. I have a cracked clear on you can have free.

My advice is if you dont own a house or have huge loans to pay off, test the waters to see if its a for you. After you get your CDL I would reccomend start with part time dump trucking on weekends.Lots of small companys need fill in drivers for weekend help. Its a good way to get time behind the wheel and on job sites. to find solid work it really helps if you have honest friends in the buisness. Not just so you can work for them but for there contacts if they dont have any work for you. It also helps if IT STAYS DRY!. here in Chicago people can get $75-$80 an Hour for semi dump trucks, $100 an hr and up for low boy moves depending on the machine moved permits etc... Some times we charge by the load and get $210 a load if we haul out of down town to a far away dump. most dumps are charging around $50 clean clay. Some dumps close to the city are charging $65 and up!!!. 4 loads a day in traffic is about all you will get unless you go back for a 5th "preload"to get rid of early the next morning. So its good if all the stars line up the night before. If you get D.O.T fines or mechanical trouble your day wages is likely wasted or even worse puts you back. I am very suprised how some of the new guys buy a brand new 100k rig to play in the dirt. and cant figure out why they have no money. Most of the small outfit guys that have been in busness for a long time still like to use older equipment because it sometimes more cost effective. I see new lowboy trucks alot but the majority of the dirt trucks are all 7+ year old macks. so in the end test the waters slowly. and learn from what the successfull owners did to survive. Let us know what your plans are. Trent

Not shure if this is the "exact" engine in your truck but take a look. Welcome to the site Trent http://www.macktrucks.com/assets/mack/prod...i4271001417.pdf

Thad with most macks you can use the first few numbers to find the models "standard" version. I cant find a RS/RL755 in my book but for some examples look at Dan Brunos web page for 1977 RS/RL models. http://www.stlouisdumptrucks.com/convoy9-04b_007.htm A RS/RL786LST will have a 6 cyl 285 hp mack A RS/RL795LST will have a V8 mack with 325 hp ....etc.... the digits after the model number are most likely the build count. When you get the whole 13 vin number you can contact the mack museum and find out what the truck came equiped with including options from the factory. I just looked and it again and it looks like that truck will make someone verrrrry happy. wish I had more room. it would look great next to my RS. Trent

I stop counting at around 95 deg. its been hotter than that all week with the heat index.

Thats a good looking truck Thad. It at the right price also! I would love that truck parked next to my RS !!!It does look to be a RL looking at the thick rear rails. Sounds like you got it down with the RS RL diffrences RS700"L" is a standard designation for lightweight models. I think the alum doors were an added lightweight option. Like said above Alum rails if not looked after properly can cause problems later on. I would not want a used truck with alum rails and heavy rears for the reason of added stress to the rails. Its not commonly seen to spec a truck with lightweight alum rails for heavy haul use. at least not in my aera. The few RL six wheelers I have seen with alum rails all had frame cracking issues. Just my opinion on your rears spring comment.

Nice looking Rig there. She has come along way. Whats her specs? trent

I leave San Jose at arond 6pm local. I figure 4 hours to Reno so I most likely will just miss you? you might see a few race rigs going East that leave later than me. Im team driving this trip otherwise I would stop to say hello in soda springs or some place at the top of donner pass.Anyways I will look for you over the pass if I get held up. Trent

Good info rob, Thanks again for the help I found the "K" wire online. I will order it when I get home if its to pricy from the dealer. Trent

Im heading down I 80 on sunday night from San Jose CA to Chicago IL. If I see ya along the way I will give a hollar Trent

Great pics Barry Do you attend the show and work the Watts mack booth? Some day I will be there, hopefully with both trucks. \ Trent

now thats the way to go Trucking!!! looks Great Jeff, keep up the good work with those machines

therabbittree The probe is just after the turbo in the exhaust elbo that points down towards the frame rail. Both the probe and guage were bought new in December 05. The wire that went from the probe to the guage was standard wire that would be used for lighting. I replaced it with new wire when I installed the new parts but Im thinking its not the right wire or length for the applacation. I am going to buy the factory wire from MACK when I get back home next week. hopefully the wire I used is the issue HK Im getting around 16 psi at full boost in summer 18 in winter. I thought 20 PSI was normal also but thats just what I heard from other people???The air compressor does have a 1" line from the intake manifold to the compressor. I dident think of that as a possible leak issue. I will check that line and check the charge core for leaks. My Air filters were replaced last summer and I have low milage on the truck sience I replaced them. good ideas thanks again Trent

Thanks guys I gave the screw about a full turn last winter. locked it and left it alone. All was fine bob tailing but with a trailer EGTs are seam a little high. The security wire was still on the housing before I turned it up so I think it was at stock setting before I messed with it. I did replace the old wire lead from the guage to the probe. the old wire had the excess length coiled up and zip tied. I will buy a new wire lead from MACK and install it to see if my EGTs change. I thought someone said that the length makes a diffrence? We will see Thanks for the info Again