On my 89 mack rd690 it has a single stage jake so I thought. Was working on the the fuse panel (had a blown selinoid that works the key switch and noticed that the fuse for the "Jake relay" was missing. The fuse for the jake back up was in place. Moved the fuse from the emergancy lights over to the "jack relay", same amp to see if it made a difference. What happened is at idle the jack almost shut the the motor down. Is this a two stage jake or a super jake that I am not taking advantage of. ? Did not run the truck yet with the fuse in place because I would have to shut the jake off when at idle.
There's a switch not working somewhere. The Jake should cut out at a predetermined rpm so that it doesn't stall the motor at idle. Did you try the Jake on the road to see if you had more braking power? This will tell you if another head came in with the fuse.
The JAKEs have 2 or 3 switches there should be a switch on the clutch pedal so soon as the pedal is depressed the JAKE turns off there is a switch on the throttle to turn the Jake on with the foot off the throttle. Depending on the engine the JAKE has a oil pressure switch mainly found on two stroke detroits. The one thing you have to watch is JAKE stall while driving down the road what I mean is shifting with the JAKE on and it stalls the engine. It sounds like your truck the JAKE only runs on all 6 cylinders are you sure its a JAKE and not Dynatard ? I think you will like it with a JAKE so you save your brakes and you can annoy the neighbourhood :Cowboy If its a JAKE have a shop pull the valve covers and adjust everything so the JAKE works at its best.
Jmac, I looked back to your original thread when you bought the truck, and according to that it appears you have a Mack Dynatard engine brake, rather than a Jake brake. they work very similiar to Jakes, and may have similiar control switch locations, but it may make a difference as to how many settings there are. A Jake usually is settable from 0-2-4-6 cylinders activated. I'm not up on Dynatard brakes, so can't say for them. It shouldn't be able to kill your engine at idle in neutral, or have any effect on it at all. Apparently it isn't being turned off at the correct RPM. Some Mack fuel pumps are listed according to if the truck has a Dynatard or not, so there may be a switch or control there that could need inspection also. Good Luck with the troubleshooting.:thumbsup
did my research and yes it is a dynatard (sounds like retard) has one setting on or off, put the relay fuse in but no diference in how strong but does shut of at idle now or when you take your foot of the pedal. I was told that the dynatard is not as strong as a jake but it does slow the truck good, just doesn't put you thru front window like I would like. Thanks
The Jake brake really only works well on Cummins and some 2 stroke Detroit engines. I don't know if they make JAKE heads for older Mack engines. The retarding power all depends on the compression of the engine and how well the JAKE is set up. It also depends on your engine size the Mack engine in your truck isn't a big displacement compared to a 855 Cummins. Some kind of engine retarder is better than nothing the problem you have is the transmission isn't enough gearing so when you gear down the engine over revves.
Very true, I find myself braking to keep rpm's below 20000. Same thing going up hills, wish I had a 3 1/2 gear for climbing. 3rd gear is about 20 mph. 4th gear is about 40 mph and to high when pulling a full load. my gearing goes like this: 1st about 10 mph 2nd about 15mph 3rd about 20-25mph 4th about 25-45mph 5th about 45-70mph Use R low when backing all the time but never use 2nd or 3rd low, use 1st low when pulling away from pile in mud only. in the middle is the week link. Next year I will buy a 12 speed.
Whats that thing got in it?!
It is a Mack RD690 with a EM6 300 hp motor and Mack 2070 7 speed tranny. It was a very common Mack set up in the late 80's and early 90's. Lots of power in lower gears, I would say it is set up for gravel pit and heavy hauling at slow speeds. Has lots of power at slow speeds but over 35mph will run out of gears real fast when pulling steep hills, flat roads no problem hauling 16 yards (over my 55k lbs limit, no lift axle). The truck will haul that same 16 yrds up a steep hill but in 3rd gear at 20mph. 1st Low is around 3 mph. The truck does what I need it to do for now, a lot better than my single axle GMC. I made more money with this truck in last couple of months than I ever made with my GMC that would hold 5 yrds and not very well at that. Like Ford9000 says a 12 speed next year will fix the issue, just can't spend the money this year. The truck is geared to low IMO, never need 1,2,3 low gears. Would be better to have 4,5,6,7 low and high.
I noticed that I never seen a Mack engine rev 20000 rpm :bouncegri The 300hp-6 and 7spd is more of a redimix truck spec good for working placing concrete say doing sidewalks etc where your crawling along a road. For a gravel truck spec where you are doing multiple trips in one day you need the gearing for the highway speed. Those old Macks pull the best at low rpms and if you want any highway speed you need some gearing behind it. A 12spd Mack or 13spd Road Ranger would make the truck more liveable to drive but it will cost some $$$$ to do the swap.
Your correct the truck will not rev at 20000 unless I am going down a hill using jake. The truck pulls the hardest around 15000 rpm and will max out at 17-18000 rpm. Next year I will try to swap the tranny out but over all I am very happy I bought the old Mack, sure is a tough old truck! I have got used to driving it double, triple cluching all the time my knees get tired after a day of driving. I plan on keeping it so putting some money into it will be alot cheeper than a newer one. On another topic, my tires seam to wearing very fast. What should I expect to spend for 8 retreads and 2 floats. I check inflation all the time so it is not that. I think it is part of the cost of trucking. Any idea on how many miles tires and brakes should last under normal use.
Jmac, I think they're making light of your #'s You added one too many 0's You must mean 2000rpm, not 20,000rpm right? An easy enough mistake too make:yup Either that, or you really do have a special Mack.:bouncegri
You should practice floating the transmission it will save you leg from shifting you can shift without the clutch just have to be smooth and carefull. The Macks are tough old trucks you have to have a good drivers seat to help with the break your back camel back suspension. For drive tires if you are doing mainly highway the Waste Hauler Lug (bandag BDM) works good. The Goodyear retread G177 is also good wearing tire For supersingle steer tires Goodyear G286A SS is a common tire alot of the guys run them here. The Hankook AH10 Supersingle is a decent super single steer tire. For supersingle steers expect to pay anywhere from 500-700 dollars for recapped drive tires around 300-340 each. I can't remember what your truck has for tires if they are 20" or 22.5 or 24.5. For us steer tires last anywhere from 6 months to a year for drive tires they last about a year if they are not abused.
I'm bad, maybe I am the retard with dynatard! Two many "0"'s. Thanks Jeff for making me feel soooooooo stupid.
Ford do you get any core money back for the old tires?
Sorry, that really wasn't my intention at all. You should get a trade in price on your old tires if the are vigin casings. Most likely not if they were previously capped. They can't have any exposed cords, large punctures through the face, or any sidewall damage. Prices here should be better than LT's prices in Canada. For the drives, if you have your casing capped $125-$150/tire, their casings $175-$200/tire. It may have gone up some since oil is so high now.
Jeff thats ok I don't mind at all, the way you, squizzy, and digger go at it all the time I can take all the razzing you can dish out I like it!! I feel left out sometimes, I can play in the sand box too.
:thumbsup Cool!! I wasn't sure if you were serious or not, so........ Digger,we have a new victum, woo-hoo!! (It'll give Squizzy a break too):bouncegri
I can't even buy Michelin 10 ply light truck 16" tire for 200 dollars. For us to reshod the back end of a tandem dump is around 2500-3000 for recaps. Sometimes you can get a deal on virgins (new) tires the Double Coin usually are cheap but they don't last long. Contractors were getting deals on Kelly Springfields. Truck tires are cheap compared to the tires used on Articulated dump trucks like Volvo A25s for 6 new tires is 26,000 dollars and there is a 6 month waiting list for them.
I'm running Cooper 444's on my drives. With everything, trade in's, FET, mounting, etc. they were betwwen $2200- $2300 for all 8. They've been wearing very well, and I expect to get 350-400,000 miles out of them, as I did when I had them on my Freightliner. This is strickly on-highway running though. http://coopertires.com/us/en/ProductDetails.asp?ProdType=RMT&id=16&title=Commercial+Tires My Dad has 19.5's on his motorhome and pays just as much for them as I do my tires.:spaz
Jeff, Is that straight mileage, meaning one wear/tread layer for 400k miles, or is that the total for the casing with multiple caps? I've never been around OTR trucking much so I'm just curious.
You need to find a good tire shop and deal with them all the time then you get decent deals and less chance of getting screwed. Most of the time if there is steel showing or stone drilling down to the cords the casing is rejected. If you run the tires down to 20-30% tread depth the retreader has some meat left to grind the old tread off. The Supersingles usually are not in demand for retreading because you can't use supersingles that are retreaded for steer tires. Some guys are running supersingles for drive tires.
That's taking the new tire @ 27-28/32nds thread, and wearing it down too 2-3/32nds. I then trade those casings in on another set, instead of capping them. I should rotate the tires, front drive to rear drive, but I don't, so actually my rear axle wears out tires about 50-75k miles before the front drives do. I'm not exactly sure why it works that way, it just does?? I've nothing against caps, but with getting a trade in on the virgin casings, and the tire price being reasonable, I feel it's a better deal for me going this route instead.
With dump trucks being in such abusive conditions recaps are tougher because the tread cap prevents a puncture through the tread. I'am not sure what kind of terrian Jmac is running for us you need to run a deep lug drive tire a regular highway tire turns into a slick when running offroad. The tire Jeff suggested is the same ones used on one of the local lumber trucks it came on the truck from the dealer. The truck gets stuck in a skim of mud or dirt with the tires. They are good for the highway and wear good but definatly not meant for offroad use.
This is the other drive Cooper offers. It "looks" like something more suitable for off-road, with an open shoulder. It reminds me very much of a Bandag cap thread I've seen before. The thread design mine has is very similiar too the Bridgestone 726 (almost a copy)and Bandag has a cap thread similiar also. http://coopertires.com/us/en/ProductDetails.asp?ProdType=RMT&id=18&title=Commercial+Tires The closed shoulder is more suited for highway, and is alot quieter running.
This tire tread is a common one now for on and off road use www.hankooktire.ca/product/tire_t&b_detail.asp?pid=21 This one is the most used works good on dumps its what we need for mud and rough terrain. www.hankooktire.ca/product/tire_t&b_detail.asp?pid=24
I do belive that without engaging the interlock between the axles most of the power is directed at the rear-rear axle. I see this alot with the KW I run. Please correct me if I am wrong on this.
I think that's right. Well Orchard, I decided I'd better check my records (shoulda done this before I posted this), On the last set of Coopers I changed out the rear ones at 284k miles. Couldn't find the paperwork for the front, but about 50k more out of them. So still along ways from the 350-400k I posted. I did get over 340k on a set of Bridgestone 726's once, but they are a better quality tire than Cooper. Steers have been just terrible. Irregular wear has me yanking them at 50k(Cooper steers)(worst)-120k(Michelin XZA1's)(best)
The wear rate probably went up when you got that curb/stake/pedestrian hunting fetish:thumbsup Confusion is forgiven (even expected sometimes). I was just wondering how often you had to change truck shoes on the Mack:bouncegri
It's about half as often as wheel/pinion seals:crying& camshafts & injectors & power diver lock & &:crying :crying