haulin-gas

Air/leaf or as some refer to it as the Z spring. Some are stamped Mack and some are Hendrickson.

It was in the shop for 11 days while they replaced the whole rear suspension. It started out as just a replacement of the pivot bushings, which had seized for the second time in less than 2 years, and ended up with new hangers, bushings and blades. Actually it made it worse because there was no "give" in the beefed up blades. Any type of ruts or uneven road surface and I had to engage the power divider or it would just start to spin. My new CHU has the AL suspension and I love it. I met the corporate sales manager with Mack Canada and he said he has instructed the dealers to avoid the Twin Y for western and northern Canada unless the customer plans on pulling no more than 80000 lbs and staying on cement highways. Mack still insists there's nothing wrong with the Twin Y, only the application that it's used in. According to them, mine was the only one that ever had issues so it's nice to hear there's been cases all over North America. Guess mine wasn't so "special" after all.

Well, after 22 months of fighting with the disaster known as Twin Y, it finally came to an end. After Mack invested an unbelievable amount of money and my time into this suspension, frame crossmembers and transmission,they gave up and agreed to get me out of it. Dropped off the truck at the dealership and am just waiting to take delivery of a new CHU with AL suspension and an Eaton 18 spd. I would rather have seen them take the truck back and write me a cheque for my 90 + days of downtime and the 4 sets of tires it went thru, but that will never happen. Hopefully the new truck will be reasonably trouble free. Hell, it couldn't be any worse, could it? If anyone out there is even remotely considering the Twin Y suspension, RUN AWAY AS FAST AS YOU CAN before you have to endure all the B.S. that I did. Thanks to everyone for your ideas and listening to my rants over the last year.

1800 km trip and no change in the handling problems. After 35 years of trucking this pile of junk is gonna put me under.

Today was day 10 and they finally got the parts in this afternoon. Can't fault the service department when corporate hasn't even released the "new and improved" parts to the public yet. So tell me, if Mack insists there's nothing wrong with this design, why have they changed all the parts?

Well, day 3 at the dealer shop trying to replace the rear suspension bushings. They had to cut the huck bolts and remove the hanger brackets from the frame to get the blades out. One of the bushings required 20 tons on the press to remove it and another one was up to 30 tons when it started to deform the blade. Now they're waiting for a new set of blades to be flown in. Better ride, 25% improvement in tire wear the brochure claims. Couldn't even get 180,000 kms (111,000 mi) on a set of drives. Think they better rename it the Twin Edsel suspension. No wonder that Volvo wouldn't put it on their trucks.

Yes, that's the lower shock mount for the Twin Y. (I wish they'd supply some KY, it would take away some of the pain in my ass!)

Another fault is the shock mounts. I recently went thru a CVIP level 1 and was given a warning that the shocks were loose. I pointed out to the officer that the brackets are made of 5/8" solid steel and it's impossible to draw it tight enough to keep the shock from moving. He gave me 7 days to repair it. All I could do was squeeze in a thin washer to take up the slack, but that only lasts a couple weeks and it wears thru the washer.

Well, to anyone else that has the misfortune of having the Twin Y suspension, my condolences. Almost 2 years into the truck and the handling problems are still not resolved. The latest discovery about this nightmare suspension is that there is no articulation in the axles. Put a jack under one side of the axle and start lifting and within less than an inch of the wheels coming off the ground, the other side lifts off as well. Since the axles can't flex to follow the road, it's forcing the frame to constantly twist which in turn wreaks havoc with the steering geometry. The dealership discovered the pivot bushings are seized to the bolts and need to be replaced for the second time. Mack refuses to pay for it claiming that the dealership didn't install them properly last time. The dealer has agreed to foot the bill but is this supposed to be a once a year replacement job? At $3000 a pop, not likely!

They didn't change the injectors, just the cups. After 3 weeks it started to pressure up the rad again and oil pressure started dropping. Took it in and they ran a battery of tests on it, finally changing the egr cooler. Mack had them change the oil pump and after a run-up on the dyno the oil pressure dropped well below spec again. (14 psi) at idle. They've changed all the sensors and verified the readings with manual gauges and still have no idea what's causing the loss of pressure. I'm thinking there's a crack somewhere in the oil gallery, but then I ar just a truk dryvr. This "great up-time" slogan they use needs to be put into the trash can.

A couple of weeks ago the dealership changed all the injector cups because it was pressuring up the rad and blowing coolant out. That problem was solved, but now the injectors rattle and knock like an old gas pot with the distributor advanced all the way. Seems to only do it when starting out from a stop or when cruising at a constant speed and then opening up the throttle. Constant pulling under full power and it seems to be ok. No check or warning lights on and as far as I know they didn't do any program changes to the ECM. Any ideas?

Stay away from as many Mack components as possible. Especially the twin Y suspension, it's the biggest disaster since the Titanic! I can't complain about the MP8, other than it needing a little more torque. Our company fleet is powered by Cummins 550's and the Mack struggles to keep anywhere close to them, except when it comes to the fuel pumps. On a 4200 km rounder up the Alaska highway and back, I consistently use 600 to 700 liters less.

It originally had M799's on the back and R260's on the steer. Currently running Michelin XZA1 on steer and XDS2 drives for the winter.

Well, it's been over a year and still no issues resolved. Filed a formal complaint with Transport Canada's Defect Reporting and Recall Division. Let's see where this will lead!

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