graham1948

Rob, Thanks for that. The front springs were done by Dobinsons in Rockhampton. They are normaly very good and professional. I guess the guy doing the job just had a bad day. All the best. Graham

I have discovered the problem with my lopsided B model. Nothing too technical, when the guys reset the front springs they put thirteen spring leaves on the right hand side and they only put twelve on the left hand side. No wonder the old girl is half an inch lower on the left hand side. The shop is full of opologies and say they will fix it as soon as I can get it back to them. Thanks for your consideration. RegardsGraham

We replaced the compressor with a new one and since then we have covered about 3000 miles without incident. It took about 500 miles to get all the junk out of the lines and they are now beautifully clean. Thanks for your help. Regards Graham

Recently I noticed that the springs on my B Model were a little flat so I decided to put her into a "spring specialist" to get the job done professionally. Big mistake, should have done it myself. I knew I was in trouble when he kept reaching for a bigger hammer to remove the stubborn pins. One whack too much with the really big hammer and this rockape broke the left hand side rear spring hanger. Never mind he said, 'it was probably already cracked". Two hours latter he whacked the right hand side hanger and broke it as well. Two days later we managed to locate two new spring hangers and a mate and I fitted them and decided to fit the new rear springs ourselves. Job complete and now the old girl is riding about two inches higher. Last Monday I decided to get the front springs reset so they would match the rears. I got a different shop to do the job this time and they did a really good job, but I notice that she is half and inch lower on the left hand side in the front. Is it possible that Mack Trucks Australia put a spacer on the left hand side to build it up to compensate for the camber of the road? The left hand side of the truck for us is the passenger side and it is on the low side of the road. The guy who did the front springs said there was a piece of steel under the centre bolt locating block about half inch thick on that side but he did not put it back because he thought it might have been there to compensate for sagging springs. It seems now as though it may have to go back. Any advice? Regards Graham

I tried both those methods and they worked until I had the gearbox out last week. Now she is all back together I have a slightly different rattle. Sounds like metal on metal and when I put the bungy rubber on it this time it makes no difference. It's not loud but it shouldn't be there. It drives me even crazier than I am. Graham

Rod, I agree with that old clip from Stan. I've just arrived home from another 500 klm trip and I find I shift the quad best when I don't think about it. When I'm concentrating and trying to impress someone I stuff it up all the time. I've just pick the old girl up after having a new throwout bearing as well as new clutch and pressure plates and I must say she is very different to drive even though I only use the clutch for stopping and starting. I don't know why she is so much better to change now, but it is. If I could only get rid of the annoying tinny rattle that is coming from the compound gear lever I be a happy guy. Oh that, and getting her to go faster than 48 mph. Do anyone have a clue as to what might be causing this tinny rattle, if I put my hand on it with the slightest pressure in the absolutely correct position (about middle of the gate) the rattle goes away. Is there a felt or nylon washer or packing that supports the gear lever. The main box lever does not rattle at all. Regards Graham

Rod you need a faster diff mate. I got a few guys looking for me in the States. I think I should have one within the next few weeks. I'll let you know. Regards Graham

Rod, I just don't want to see the dog's eyes watering, I want to see him with his paws over his eyes, just peeking out between his toes. How fast does a 9 ratio diff go? Or better still how slow does it go? Graham

Herb, I just found out from the guys at Mack in Australia that my B model was originally delivered with a tandam drive rear end with an 8.24 ratio( that would have been bloody slow). Someone in the past fourty five years has converted her to a single drive. I thought she looked a little bit longer in the chassis than I remembered my original single drive unit. Never mind I'll keep her as a single dirve and save the wear and tear on the four extra tires. Regards Graham

Herb, at last I've got the numbers off my rear end. They are ratio R 7.48. Other numbers are 11KH4159AP6 and CRD 117.63H.32. I've tried Adelmans and Watts but they are still looking. Dennis at OldMacks think he might be able to find one for me. I'll just keep looking. I've decided that if I'm going to all this cost and trouble I may as well hang out for something that will give me decent speed. e.g something in the 4's. Regards Graham

Again many thanks Herb. I'll get the serial number and then I'll talk again to Adelmans and also to Watts who are both looking for a diff for me. Regards Graham

Herb or anyone who can respond as soon as possible. I have just spoken to Rick at Adelmans and he thinks he may be able to supply a diff for me that is either in the high 4's or low 5's. He wasn't sure about the serial number of the diff. He mentioned a CRS 84. Is that the part number I am looking for? Thanks Graham

Herb, Gearbox out and top off. The workshop foreman reports nothing abnormal. Bearings OK, he reports some sign of minor rust on the gears but nothing to worry about so I told him to seal it up and just concentrate on the clutch and pressure plates and the throwout bearing. Hopefully the rattling noise I was reporting was to do with the throwout bearing not disengaging. I guess I'll know in a few days when they get her back on the road. Next trip is in 10 days, we're off on a 2000 mile promotional trip for our country music radio network. Regards Graham

Tom it would be great to be able to tell people the old girl is capable of doing 100 mph, but stuffed if I'd like to be hanging onto the steering wheel at anything over 70 to 75mph. I drove one for 5 or 6 years in the late sixties and she was capable of 75 mph. It was a lot of fun chasing the steering wheel all over the cab, but then I was just 25 years old. 60 to 65 mph will do this old fella now that I'm 60. Thanks for the equasions, I'll have a few beers and then try to work it out. Regards Graham

Herb, I've put my B model into a workshop to get them to replace the throwout bearing (the current one is not dis-engaging and is making a hell of a noise) and whislt they are at it I thought they may as well replace the clutch plate and the pressure plate. Like all shops today they claim they know everything but in essence they only know modern trucks. They tell me that because they can't buy a new clutch and pressure plate for my truck they will have the old one rebuilt and fitted to the flywheel, which sounds OK to me. While they have the quad box out I asked them to lift the top off it to see if the bearings etc are OK. Do you have any advice as to what else they should be looking at, and are there any recomendations you would make in relation to this operation. I have also asked them to look at the issue I have with low RPM's and I have given them the print out you gave me from the manual re this topic. I still can't find a faster diff down here than the 7.48 currently in the truck. I might have to find one over there and ship it over here, any clues? I want to be able to cruise at better than 60mph. Regards Graham

Best I seem to be able to do down here is to get a 6.36 ratio diff and the general consensis of opinion is that I should be able to maintain at least 64mph on the highway. If that is so I will be happy the added momentum will have the effect of powering me up the other side of the hills. At the moment I don't get enough run up to power me up the inclines. Herb, thanks again for the great help in relation to the air cleaner. Today we'll work on the linkages and I'll make sure that the strainer in the air clearner is clean. We are not blowing black smoke all the time, in fact she is a pretty clean runner, just black smoke on take off and when she drops the revs a bit. Many thanks Graham

I reckon they are full of the brown sticky stuff too. Too many desk jockeys who have not have the practicle experience. This week we are going to get the revs right. We have a lot of loose play in the linkages and we are not getting the throtttle open enough. Looks like I'll be able to get a 6.36 ratio diff and with the improved revs and the faster diff I should be able to get to 65 mph. An old guy down here tells me my air cleaner is too small for a C motor and maybe we are not sucking in enough air for the big turbo. Mine is an air cleaner from a 711 and he says I should either get a C motor air cleaner or install a second one on the other side of the cab to get more air on board. How does that sound? Regards Graham Forgot to mention there is a couple of photos of my B model posted under Vibrations in B model that show the air cleaner if you want to have a look at it. Thanks Graham.

Yes it is a front loaded diff. Does this present a probem? Graham

I am interested to find out which diff ratio would be the best to allow me to maintain a cruising speed on the highway of about 65mph or 110kph. I have a single drive B model with a 250 turbo C motor coupled to a quad box 7220. Currently I have a 7.48 radio and it is suggested that a 6.36 ratio will allow me to do 65mph but a friend of mine has a 6.36 ratio and he seems only able to get it up to 60mph. I am revving out to about 1900rpm. Operating range seems to be 1200 to 1900rpm. Mack Trucks in Australia told me that the old Mack engines like mine usually operated at that range. I told them I was expecting to rev it out to 2100 and they said that was too high. Any thoughts? Graham

Well here I am back from the outback and another 1500 miles successfully completed in the old B model. I found out why she won't go over 48 miles per hour. She has a 7.48 ratio diff. I am desperately looking for a 6.36 or better, but they are as scarce as hens teeth down here. The noise in the gearbox is a lot better since we changed the oil and added some Morreys additive. We know have discovered we have a bad throw out bearing. It won't dis-engage, so it looks like the gearbox will have to come out, so whilst we are at it we may as well do the clutch and pressure plates at the same time. Anything else to look at while we are doing it? Our oil pressure at full operating temperature runs at a constant 75 psi, I am happy with that, but what should it be. She pulls her head off and I am extremely happy with the way she performs. We are pulling a pan with a gross weight of just 10 ton, so all up we gross about 16 tons. I will be in the States in a couple of months and I thought if I can't get a suitable diff over here I might be able to get one over there and ship it home. Is this possible and what do you think I would have to pay for a good unit or better still a remanufactured one? Regards Graham

I'm pulling the compressor off on Friday to overhaul it. At the same time I am going to try to track down a few other oil leaks etc. New sump gasket for a start. A friend of mine with a B61 has a noise at the front of the engine that sounds like it is coming from the harmonic balancer. It has only just started and it is like a knock of some sort. Someone told him the harmonic balancer has fluid in it and if the truck has been standing the fluid goes hard. Is this so, and if so how is it fixed? Graham

First Gear, I'm in Gladstone Queensland, how much do they want for her and is it still available? Graham Can't be worth much the dogs missing from the front. Graham

Bloody hell...that's what I thought. Today I took the starter off and reconditioned it, getting the compressor off is a bit more difficult, jammed right up against the steering box. But if it has to be done, it has to be done. Looks like I'll be under the old girl again tomorrow, pity it's not a 23 year old blonde. Thanks for your help. Regards Graham Forgot to mention that First Gear was right on the money last week we did have oil coming out the air horns. Never mind, I keep telling my wife, it's only money, tresuary is printing more of it every day. Graham

How much oil is too much oil to be getting into the air tanks on a B model. Recently on a 2000mile trip I noticed I was getting oil into my air tank. About half a cup on the first tank from the compressor, just a spray into the second tank and nothing in the final tank. Is this normal. Some guys tell me this is normal and I should just get into the habit of bleeding the tanks everytime I pull over, some guys tell me to have the compressor overhauled, but if it is not necessary I would rather not do it. Any advice would be appreciated. Graham

Thanks Herb you've been most helpful. First of all I'll get someone here to do a genuine test on how many RPM she is delivering. If she is topping out at 1800 to 1900 I'll get them to make the necessary adjustments then we'll she what she will do before we play with the diff. The general consensis on the noise in the gearbox in forth and fifth hi-split is that we should first change the oil and she what happens. Regards Graham