Kav

the person that did my heads said that it showed very little engine wear so i thought it must mean rings should be good. the truck has close to 500,000 KM. on it.

Hi jook24 - Have you ever changed the rocker shafts on the heads. We had trouble with two different motors where there was oil dripping out of the breather pipe even after the motor had a new piston and sleeve kit. We found excessive clearance under the rockers as they had grooves worn into the shafts. When we changed the shafts the oil dripping stopped. We found that worn rings and sleeves usually caused excessive fumes and blow-by down the breather. One motor that had blow-by past the rings as well as the worn rocker shaft was loosing half a gallon of oil down the pipe in a big day. Don't forget that with the Mack sleeves you can still have original honing marks in the bore at those sort of miles and at the same time have stuffed or broken piston rings. Best regards- Michael.

Trunnion Bushing. The rubber type.

Yes, I've changed them.

Jack up the truck, put blocks under the trunnion.

Remove the wheels from the rear axles on that side.

Put a jack under each spring box on the side that you're changing.

Since it appears that someone has put a home made retainer on the end of your trunnion shaft, that must be removed.

Cut off the U bolts that hold the spring to the saddle.

Remove the bottom half of the trunnion saddle.

Jack up the rears so that the upper half of the trunnion saddle separates from the trunnion bushing.

Remove the worn out rubber bushing from the trunnion shaft.

Be sure that the trunnion shaft is clean and no pieces of the old bushing are stuck to it.

Using some waterless hand cleaner as a lubricant, slide the new rubber bushing on to the shaft, center it in the middle of the area where the old bushing was.

Let the rears down so the upper saddle contacts the trunnion shaft.

Install the bottom saddle on the trunnion, install new U bolts, and tighten.

Replace the home made retainer on the end of the trunnion shaft.

If I remember correctly the torque spec for those U bolts is well in excess of 1,000 ft lbs. so if you don't have a torque multiplier that will achieve that torque, have the U bolts torqued at a shop with the proper equipment, this is very important. Insufficient torque on the U bolts can lead to broken spring centerbolts, and broken U bolts, and possible damage to the truck and personal injury.

HK - That was a standard suspension trunnion set-up at one stage. I have a 1969 R model which has the same through bolt and cap on each end which was an original Mack fitment here in Australia. When you tightened up the U-bolts the rubber bush used to ooze out the same as in the picture. I broke a few of the through bolts when you did a real tight turn at slow speed- usually broke off at the end of the thread. The one I still have still has the original U-bolts and through bolt and plates. I fixed one through-bolt by making a one inch high tensile bolt and boring out the two end plates to fit. The dead axle on that model is a couple of inches shorter on each side than the later one which has the collar on the end with the bolt through it. Best regards - Michael.

I was thinking about the sea foam, as an additive because I happen to have a couple of cans the the shed!

Dave

What is the sea foam that you use. When we used to have this problem from excess idling in a paddock loading bags of potatoes. we used to drop the oil out and do about a thousand miles with Castrol hydraulic oil in the motor. This used to bed the rings in again. The other way to cut the glaze was to put a couple of teaspoons of Bon Ami cleanser into the inlet manifold while the engine is running. You cant do this too often as it will wear the rings out. The old Caterpillar books used to describe this in detail. If your rings are totally gummed up, some of the newer additives would be better. Heavy work is the best cure.

Michael.

Hello Fellow Mackers, does anyone know how to adjust the powersteering box on a 1975 R model ? mine has lots of play in the wheel and I need to adjust properly. Thanks

Hi Wolfwalker -We had an Australian built 1974/75 R600 with a Shepherd Power Steering Box fitted as original, and I wasted hundreds of hours working on the steering and rebuilding it and I tried everything to get the play out of the wheel without much success. I was told that because they had a lot of turns lock to lock, it was impossible to get them tight like the later Shepherds and Ross Boxes, which were much more direct. From new they had a lot of free play in the wheel. Eventually we went back to Power Assist which was much more safer on the road. Other model Shepherds of that age may have been better but I could not find one - Best regards - Michael.

Hi Maxville. Why cant you set it up the same as the standard Australian Mack Trident with the Tri-drive which is used in the Northern Territory to pull four or five trailers. I think they use a fairly standard Air-bag suspension with two front through drive axles and one rear axle.- Michael

Had the ol 237 tweaked a little-any merit to installing a bigger turbo?-Kevin

Hi Kevin- In the past we used to run the 237 motors with the pump set up exactly as a 285 and we put the 300/350 turbo on them. You must fit a bigger Air cleaner to the truck the same as the E9 V8, as the original cleaner is too small as it builds up a vacuum going up a hill even at 237 with a new element. An air scoop on top of the Air cleaner also makes a difference. It is a good idea to fit a turbo boost gage as the boost can go up to 35 psi when you first start the truck on a frosty morning. You have to drive them by the Pyrometer as the exhaust temperature will go up on a big hill, so you just have to change gears a bit sooner to stop the Pyro going too high as you dont have any intercooling. We had that system on three different trucks and they all worked very well. We used to have some trouble with the early 1970's type Maxidyne Pistons but when they changed to the Econodyne type with the top inserts, we did not have any more piston failures. The old ones used to fail occasionally even with a standard 237. If you have a reliable driver you wont have any trouble. I still have one truck set up like this and another one that I used to own is also still working every day. Best regards - Michael

You da man Rob! Agian good job !Idle should be set at 650 I hate it when they idle fast!

Hi Rob - Its great that you got it going well. In 1982 I got caught with the same problem as I said before. I took my pump to Mack Trucks in Brisbane and they charged me over $1200 to fix it and they did not even put the pump on the test bench. Since then we have done the same job ourselves for about $100 each time with the same results and you don't have to pull the pump off. Did you check the gear levers and selectors on your gearbox. If the lever is sloppy you may be able to build them up again. It might only need the bottom of the gear levers building up, which doesn't take very long to do. Best regards - Michael.

Hi Rob - We used to have a similar problem caused by worn governor weights in the Ambac Injector pumps in the 237 and 285 Maxidynes. The revs would roll from 500 to 1000 rpm while they stood there. It changed when you parked on a slope with the front of the truck either up hill or down hill - I don't remember which. We used to re-bush the weights and put new bearings in the governor and it would fix it up. I don't know if the V8 has a similar governor, but it sounds like the same thing. Best regards - Michael.

There is a new book just released about the LEADER trucks which were built in Australia during the 70's and 80's. Most of them had a fibreglass cab very similar to the Mack F and FR model day cab. Very strong rumours are that the first Leader was built in the Mack workshop beside the Mack Factory at Brisbane. The book also covers the early days of Mack Trucks in Australia with a lot of great pictures of the early trucks. Check the website below for a preview. Best regards to everybody - Kav from Oz.

www.blueflyer.com.au/leader_trucks.htm