ropensaddle

For lube on those rubber trunnion bushings, I always put some Mr. Clean in a spray bottle, wet the bushing with the Mr Clean, then smear a coating of D&L or GoJo waterless hand cleaner on them too. That combination makes things slipperier than shit. I use that for a lube on the Chalmers suspension bushings nowadays on the Internationals where I currently work.

Regarding the camelback U bolts, I have seen them break in service, also have seen the spring box attaching bolts snap, so it's cheap insurance to use all new hardware.

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I understand new fasteners are the way to go impacts heat them up and sometimes u bolts get hot just wrenching. I however have seen idiots in trucks that it would not matter if you replaced every bolt daily they would still break them!

I would like to add to rep, is there a minimum post count before actually helping someones rep? If so I will be posting before repping

I have seen alot of guys use the torqe multiplier on the trunion U bolts to get them tight. run the truck for a few days and then check them again. I agree that the urathane lasts longer. I think you can get them for the trunion and pads that are between the main spring at each axel end.

you should notice that the rears track better in hard turns and dont dog track going down the road. IMO Ride comfort is not noticed after new bushings and pads are installed...

It feels more stable then thats what I am after. Mine feels too top heavy going in turns, of course the grapple is heavy so; it actually is lol. I am wondering if I can break it loose with my cheater too! I am going to call the spring shop and see if they have done enough of them to give me a worst and best scenario; knowing that they at least will be changing insulators!

When you changed the compressor did you check the cooling lines for restrictions. I'v seen them rusty and blocked behind the pump. Also was the compressor pulling air from the negative presure side of the turbo? Mack had a service bulletin about moving this hose to the intake manifold at the rear of the engine or installing a filter at the compressor. Low/no cooling or restricted intake can shorten the life of your compressor.

Yeah it is going in between filter and turbo I will get a filter kit soon. Good waterline flow!

It depends on if you use OEM or aftermarket vendor parts. You'll probably have to shop around. Here are some pictures of the trunnion setups from the Euclid parts manual so you can see the difference in them.

Trunnion Type Comparison.pdf.

Thanks I would rep you but I am neutral is it 50 posts before you add rep? I either have the two piece or one piece cause I don't have a cap like the bronze! I will probably get the red aftermarket insulator pads I know they cost a lot more but if the are similar to the radius arm bushings like on my ford its worth it doing it once!

Not a mack but I like my lil one ton dump

Lol thats bad arse looks just like my old r but it was a little rough ride though

If the metal plates in the load cushions are exposed or there are marks on the buckets caused by contact with the "T" on th espring leaf it is time to replace your load cushions. This is not a difficult job but it does require some large tools. If the trunnion bushings (bushings on the suspension crossmember between the axles) are worn it gets much more complicated. Depending on the suspension rating the u-bolts will be either 1 1/8" or 1 1/4" for the 34,000-46,000 lb suspensions. These tighten down to 1,100 lbft for the 1 1/8" and 1,500 lbft for the 1 1/4". These must be tightened down or you will break spring leafs when loaded. There are three different trunnion bushing types: brass/greasable, one piece encapsulated rubber trunnion bushing, and two piece rubber trunnion bushing. If you have the brass bushing or the one piece bushing they will have to be pressed in. Also the one piece pushing can sieze to the dead axle making removal very difficult. When installing new insulators I would recommend installing urethane replacements as they seem to last much better than the current standard rubber type supplied by Mack. I will find a picture of the different trunnion bushing types so you can figure out what you have.

Thanks I think the actual trunnions are ok But I can't find a grease sert. I could buy a big torque wrench I usually use a six foot cheater and 1 inch drive breakover for my heavy stuff and get all I can get bouncing lol. I may just get it done at the spring shop but would like to have an understanding of the process. We have a good spring shop, wander how much it will hurt my pocket?

I want to thank you guys I have it going right again. I even replaced the broken emblems and going to rework the cap with a fiberglass repair kit then shoot some paint will post pics when I do.It has a hard life especially before I bought it all body damage done by prior owners! Anyway this is what it does for me!

What will normal re-bush cost if done in a shop verses done at home? And how much better does the truck Handel afterward? Guess should include 81 mack camelback!

News for ya!The GU won't Be here In 29 years!It will be in the scrap beside all the other throw away Trucks that are being built today!

But having said that ,Yup remeber what ya hope for!Cause a Any RD CH or older truck Even a RS tandem tandem steer is easy compared to a GU count your self lucky.

Lol I am just a wimp and that dern thing was heavy but I got it in and oil line too thanks to ya'all I searched and learned how many thanks to you guys for sharing

It's probably a bad dash valve. This document from Bendix (http://www.bendixvrc.com/itemDisplay.asp?documentID=4572) explains the function of the dash valve. Basically the dash valve has a spring that causes the inside parts of the valve to move to the exhaust position when air pressure drops below a certain point. If your compressor was pumping oil for an extended amount of time that oil has made it through the air system to the valves and air chambers and will cause problems. The air compressor was probably the root of the problem and since you've replaced it you're done with a good part of the work. Do you have an air dryer on this truck? If the dryer cartridge is contaminated by oil it can come apart and send oilly debris through the system. Good luck.

Thanks I searched it last night and came up with the same thought that oil fouled the button. No drier I will replace the chamber and brake button and hope that gets it. Thanks oh do you know the torque on the insulator bolts spring pads? I am going to replace them too!

With the spring brake released air is SUPPLIED to the chamber to hold off the spring. If the diaphragmm is ruptured it will allow holdoff air from the spring chamber to pass through to the service side of the chamber, which will exhaust through the quick release valve. This could be the cause of your slow build up time, but even if its not, you need to get it fixed.

Yes I know and plan to by weeks end. The truck is out of service until I get it all right I managed to limp home from a job but immediately started looking for the problems. I am trying to figure out why the brake button wont pop off when air gets below 25psi and was wondering if it could be this chamber also causing that. If not I was hoping to learn what was doing it, so; when I take the core back to the dealer, I could pick the chamber and whatever is not automatically setting spring brake at low air! What triggers the park brake button to pop out at low air?

Just think, in another 29 years, when you have to change an air compressor on an MP8 in an old wore out GU, you'll look back at this and remember the good ole days. A leaking air chamber diaphragm will keep the compressor from building air. Remember, when appplying the spring brake you are not putting any air into the chamber. If you have the spring brake applied and it's leaking air out of the chamber you need to check further up line to find out what is supplying air to the chamber when the spring brake is set

Lol in 29 years I will be happy if I am still alive. I did not have park brake set with them set air builds a little faster but not as fast as I thought a new compressor should! I get conflicting time amounts to build full air in pretrip info does this truck need to make full air in 3 minutes or 60 seconds? The spring brake does not set at 25 psi could that be the chamber as it is on the spring brake chamber? Thanks in advance this truck is my labor savor so I need it up and running!

Name: mack r (1981)

Date Added: 24 June 2010 - 12:31 AM

Owner: woreoutmack

Short Description: Old workhorse

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Hello friends I just put a new compressor in my 81 Mack because of oil in lines! I hope I never have to take it off again . Anyway I drained tanks twice no oil or water now but my air was too slow to build so shut truck of with service brakes on wheels chalked and air finally to 120 psi. I found a leak in front rear tandem air chamber and my question is will one leak cause the air to build very slow? I actually have to throttle it to get it to raise much. Also my spring brakes don't apply fully when fanning the button does not pop out!

Will a new chamber fix it all or just the rate of compression? I also put in some new slacks! I am trying to get this thing back in business.

Well I have been prowling a few days and decided to join. I guess I will start by saying hello I am a tree service that has and old wore out r model grapple truck that in the next several years I will hound yaáll on from time to time lol. I actually used the search already and looks like I will soon be repairing my compressor, oil coming out tank drains when flushing! Anyone else cry at the expense of owning big trucks? I would post a pick of the old brute but it was roughed up long before I bought it so its ugly lol