JoeH

The screwdriver trick I learned for motorcycles. Minor size/noise difference.

@Joey Mack

Go to your dealer and order book # 8-211!

3-4 is engine position sensor, located on the timing cover. Camshaft.

Appears your VECU power is dropping out.  This is likely the trigger for the 6-3 code, as the VECU dropping out will obviously disrupt data communication.

So some Mack camelback trucks have a torque arm on the rear differential going to the right frame rail. It prevents the axles from walking. Check to see if you have one, check condition of the joints at either end. Replace if worn.  Also, elephant pads aren't a terrible job, doable in a day, but they do take some serious torque to tighten down.  Expect to replace all bolts, you will likely be torching some off. Few different styles of pads I believe. Some use a metal side insert some don't.

Remove one side, separate, sandblast/paint, bolt back together, install, shift cribbing to other side, & repeat.

On 2/3/2022 at 10:04 AM, DieselDog5.9 said:

Just got a quote from Mack for 2 new rails.  26k not installed.  Our frame is not awful rusted but the spread is bad. 3/4 inch.

Cannot just get a whole frame rail from supplier because an R model frame is "Fashioned" in the front and they do not do that only straight frames.

Guess I am looking at 2 options:

1. Cutting the outer frame off, sand blasting and putting back together and welding. Reading here I see some have done this but couple of questions.

• Where is a good spot under the cab to cut that you can get under there and weld back together.
• Will the frame come back together as it is spread pretty far apart from original.

2. Pull the inner frame rails out

• Lots more work but no welded joint
• Will the frames come back together
• What is going to be a complete SOB when pulling the inner rails out?

Would love some more pictures of some others experiences with this repair.

This is the second truck I've done this to. Leave one side in to hold alignment of everything. Put jackstands/cribbing under everything on the other side, and pull the supported side out.  Separate by driving a long 2x6 (cut the one end into a wedge) into one end. Lots of hard work involved, be careful you can kink the rails if you try separating them like a wish bone. If it's a dump truck you will have to pull the dump body off. 

First truck we did was an RD model, the cab had to get jacked up pretty high to let the frame clear.  This one I linked is an MR, the cab tilts forward giving tons of room to work.

Also that motor/trans has a lot to be desired for on hp/gears for 99k.

If you want to haul heavier then hold out for 55/58k rears.

You want 44k rears. Simply not worth investing in an underrated truck. The 38's will hold up for a while, it'd do the work ok, but potholes will beat the truck up. And you will be getting redflagged by DOT for being over the rated capacities of the truck.

On 2/3/2022 at 8:38 PM, Lukasswaziek said:

Okay so got the read ends on jackstands, front wheels blocked. Put it in a higher gear and would drag the brakes and now I'm leaning more twords the engine making the noise. It sounds like a real bad injector knock, but for some reason just resonates in the cab. but then again I'm not hugely familiar with Mack trucks and the noises they make. Mostly worked on and drove cats and cummins. I checked the pto's to see if either one was making the noise and it's not that. If you get it at the right rpm it sounds more like a hard knock rather, but otherwise clatters with the engine firing

Where are you located? You might have an expert on here not too far away....

On 2/3/2022 at 6:19 PM, Lukasswaziek said:

So I have an issue that's been going on as long as I've owned this truck, it's a e6 350 with a maxitorque 9 speed. Between 1200 and 1600 rpm I hear a distinct clatter but only under light load and the truck has to be in gear and rolling. When I rev it up in place at that RPM range It won't make the noise at all, and when I'm pulling a heavy load and get into it, it goes away also. Sounds a little too loud to be an injector knock. Oil pressure is around 30 at idle, 60psi at 1600, 90 at 2100 and oil is clean. Just put a headgaskets in it and cylinder walls look great, all still have crosshatching and no scoring. This noise almost sounds like it's coming from the rear of the engine or more like the bellhousing/clutch. Sounds like it's right under the cab when I'm driving. I'm not sure where to start. 

Does it make a difference what gear you are in? Hi range? Low range? If you put your foot on the clutch pedal and apply gentle pressure to the throw out bearing (without disengaging clutch) does the noise change?

3 hours ago, mechohaulic said:

i'll bet you didn't try the "heater hose technic" you and others will have a good laugh . take a length of heater hose ; 1 in x 2-3 ft long worked for me. i know today they make fancy stethoscopes . hose to your best ear and follow under neath till you close in on the noise. that noise isn't bad, frustrating and making me scratch my head is ::why did i say I DO twice!!!LOL

A screwdriver is what I learned to use! Put the tip of the screwdriver on the engine or trans and cup the end of the handle to your ear and it's like a whole symphony suddenly comes to life.

On 2/2/2022 at 3:33 PM, VTS said:

We have a 91 RD with an EM7-300.  The engine was overheated and it ruined both heads, so were looking for used replacements. Are the heads on an E Tech setup the same as earlier EM7s?  There are more options online for later model engines, we just dont know what is compatible. Thanks!

Call your dealer and get the part number from the heads for your truck.  Use VIN from other years/models to check compatibility.  Chances are your head # supersedes to another number, so make note of that number to see what else might have it.  VIN #'s can be had easily from online auction/sales sites.

4 hours ago, 67RModel said:

Yea I was going on the fact that its a RD690....690 indicating a maxidyne engine. When trucks get to be this old and passed through many owners anything is possible though.....

Yea I completely brainfarted. I've been 100% focused on getting our mr688 ready for Iowa.  Stress is through the roof, we function quite happily in a 15-20 mile radius.  1,500 mile trip on a truck we have put about 25 miles on test driving since Monday!  Fingers crossed no more hiccups! This truck leaves tomorrow morning! 

Coopersburgs Kenworth had a rare? used heavy single frame MR, 2 customers got into a bidding war over it.  Heavy single is such a bonus.

Interesting. That's the one thing that eluded me. I think the technicality I'm combatting is that I'm marked Intrastate on my DOT #. JJ Keller implies most states are just happy to get the trip permit $$$, despite the minor DOT intrastate technicality, but Illinois is very strict and wouldn't dismiss it as trivial.

Regardless, my parents want nothing to do with Chicago/Illinois, so they're set on cruising Ohio to Kentucky to Tennessee to Missouri to Iowa. There's a ferry from Kentucky to Missouri but the ferry seems to have been broken down for a few weeks so the only other Mississippi River crossing (without going through Illinois) is to drop down to Tennessee.

Or the engine or valve cover is a transplant....

Or not. Looks like the engine # is labeled in the cab too...

Gauge worked fine up until the other day when I replaced the sending unit gasket.  Now the gauge is pegged down to about a 5 o'clock position...

I read 4.3 volts from positive to negative wires on the sending unit, and 4.3 volts to a known good ground. I did reroute the sending unit wires as I didn't like them laying loosely on the top of the transmission. Damaged wire strands? It had been folded back and forth about 5 times and zip tied to the fuel tank lines. I straightened it out so I could run it along the crossmember.

https://www.emanualonline.com/material-handling/industrial-equipment-tools/vehicle-parts-accessories/transmissions-gearboxes/allison/4000-series/allison-transmission-4000-series-full-service-repair-manual-emo-171892.html?currency=USD&product_country=US&product_id=171892&placement=&adtype=&keyword=&gclid=CjwKCAiAl-6PBhBCEiwAc2GOVLpvhBeptBaObblZHzI6nRoPzRU1hylOl8ZohDFiQfdTkXVURgzllxoCMOYQAvD_BwE

I believe this is the transmission manual I bought. Worth every penny. There's about 10 or 15 pdf files that it comes with for different books, but the information is very good, and has the DTC codes in it.