mack88

what would cause a clutch brake to brake.I had one put in my 12speed.used it about 8 hours started going down the road with a load heard a couple of snaps coudn't see anything behind me so i carried on.but when i stopped i found out what that was.I usally don't use the clutch to shift so had me woundering what might cause it to brake .It was a 2 piece.they set the clutch up to but i found it was kind of jumpy in first?

Hi Grant, I've never seen an eight bolt setup on a quad myself. Is this the single countershaft type transmission, or a later model 18 speed? I don't know if the single countershaft type would use the same type pto or not.

If you would know the transmission type, or model, I could check for fitment.

Thanks,

Rob

Hi Rob I put one on my truck it has a 12 speed i had to put a spacer with a gear on it to reach the gear inside the tranny.It was the six bolt side.The other side was 8 bolt but no room. Jook

Hi Jook, a 1976 model would not have had a grille in it from the factory. The shutters were the grille. The opening for the hood would have been framed with a stainless steel perimeter moulding. The western trucks were different, and could of had a full grille in the form of an inverted horseshoe with a "perforated" center section. Do you have an air to air intercooler mounted in front of your radiator? You mentioned it is a 350 Mack engine and all of those with the exception of very early ones had air to air charge air cooling. The early ones used a water to air setup much the same as the 283-285 Mack engines of the 1970's, and the 300+ engines of the early to mid 1980's.

As mentioned, the shutters on an air to air setup with a radiator mounted intercooler is self defeating as related to power and economy. It will help you with keeping the water temperature up in the winter time but so will a good engine thermostat. Shutters were basically obsoleted by the advent of the clutch fan whether viscous, or air engaged. Personally, I like shutters based solely on appearance but I'm not around new stuff hardly at all.

Rob

Thanks Rob the 1976 did not have a grill it just had the shutters as a grill.Now that you mention the shutters as for winter time warm up you could be right. when i bought the truck it had a flat deck on it. i remove the flat deck on it to put a gravel box on it i noticed some body had ran cooling lines behind the cab with quick couplers. So it probally had an engine on the back for what ever job it did.They used the truck coolant to warm up that engine.

The only reason I can make for this type of setup would be to eliminate cardboard in front of the radiator in the winter to keep heat up in the cab. Those shutters do not look like anything "factory" that I've ever seen.

Do you have an air, or electical toggle switch in the cab, or are the shutters automatic in operation via a thermostat in the coolant passages of the engine?

Rob

they are automatic usually they are closed when i start the truck but when it warms up they open.there is an air line that runs from the coolant passage to the shutters.My dad had a 1976 mack RD700 it had the shutters behind the grill,so i was kind of wondering about these.

It looks to me like that was added on at some point. Why, I have no idea.

As I said before, with a charge air cooler in front of the radiator, shutters would not and should not be used because when the shutters are closed, the charge air cooler cannot get any airflow and becomes useless.

Lack of charge air cooling will lead to high exhaust gas temps, overheating and low power.

thanks for your help i will disable it and go from there

i will post some tomorrow i am on dial up so it takes awhile to post pictuers

I cant say if it had shutters or not but i can tell you that the fan clutch will not kick in and make too much of a noise when it is engaged.Make a photo of them and post if you can. That engine should run when pulling close to 200 degress with no problem.

i will post some tomorrow i am on dial up so it takes awhile to post pictuers

Those would be the "fixed" type "shutters" just for appearance.

With a viscous fan drive you would not have actual opening & closing shutters, nor would a truck with a CMCAC (chassis mounted charge air cooler) have shutters because closed shutters would render the CMCAC ineffective.

So should they be removed and just install a screen.Or i guess maybe just unhook them maybe just for now.Thanks for all your guys help.

A 1988 RD would not have shutters.

this one has them mounted on the out side of the hood because of the air to air.I have only seen one other truck like that .So if you have a fan clutch they don't have shutters? i am a fan of Mack trucks but not to familer with the options.thanks.

1988 is a little too "new" for me to be of much use but there is a proceedure to check performance of the fan clutch in service manuals. I use a hand held phototachometer to check both the crankshaft speed, and fan speed when engine is hot. The fan should turn within a certain percentage of crankshaft rotational speed at a given temperature.

I don't know what engine you have, series of truck, empty or unladen weight, accessories etc. so these are "generalities" but the same principals apply.

Ensuring your radiator core is clean is paramount.

Rob

thaks Rob. It is a 350 1988 RD 688S I have had the truck for a year it had a new rad not to long before i bought it.

Hi. My 88 mack seems it wants to run warm on me.It runs at about 175 to 180 empty. I pull a 30 foot pintle with 3 axels my back hoe weighs about 24000 pounds when going down a soft road it will climb to 200 easly. when i stop it will drop down to 180 in a minute or so. I never here my fan roar when my shutters are open it has a regular clutch fan. Ther is some resenstance when the truck is cold. I had new head gaskets put on this spring. Thaks for any advice

Have a compression test done. Should be at least 400 p.s.i or better on a sound E6 and about 500 p.s.i.on an E7 engine. We usually do a quick check first with the manometer. Shouldn't be more than 1" of crankcase pressure under hard pull.

Oil consumption is also a good indicator of engine condition.

As a side note. Although less common, a bad air compressor can leak air past the rings and create pressure in the engine

crankcase, as can a bad turbo that can force boost pressure down through the oil return tube and into the crankcase.

when i first bought the truck it had quite a few oil leaks. it had not been used very much in the last 4 years,when the other guy had it.so i got most of them fixed. I have run 40 hours since then also did an oil change oil has'nt gone down on the dipstick, before i would be half way down. so i asumed the engine might be okay.

Piston ring & cylinder liner wear.

In my experience, Mack engines exhibiting this type of behavior usually need an in frame overhaul very shortly.

If it's actually blowing oil out the breather, that's pretty bad.

Also, bad exhaust valve guides can allow exhaust to leak by into the rocker arm compartments under the valve covers which also will pressurize the crankcase.

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 there,i have mack 350 i had new head gaskets put on.I had one back one that was leaking but just to the outside,this was last fall.So i waited until this spring to get that fixed know i now have some blow by. not a lot if i let it idle for say ten minutes it leaves a 3inch spot on the pavement.should i be concerned about this,or what might be the cause of it,or how i might fix it.the heads were fluxed so i asume they should be good.thanks

The reason it is always the top shift that grinds is that it has more rpm to change.

The output shaft is connected to the driveshaft. The faster you go the faster the mainshaft goes.

Shifting at 2100 rpm from 11th to 12th, the input shaft changes rpm from 2100 to 1632 rpm or 468 rpm.

10th to 11th is 373 rpm.

9th to 10th is 298 rpm.

That's also why you can make shifts from first over to second under on a TRQL2220 Quadraplex by moving both sticks at the same time, the gears are going around so slow they just clunk into place. At higher speeds you have to get just right or it scratches.

I thought i should change the tranny oil in it.I wasen't surprized to find filling and some small chuncks of metal stuck to the drain plugs,so maybe that is why it grinds,but sometimes it will slip ever so nicely into 11 but grind abit into 12th.

thanks for that link,like i said great site.o by the way i am from up in canada,Saskatchewan.

Hi there great site. does anyone know why my 12speed grinds in the top two gears up or down but not in the bottom three. split shift or strait shift.truck has close to 500,000 K.M on it. i changed tranny oil there were some fillings in there some small metals to. I have read that these would grind but i don't know if it should grind when you split shift,using the jake helps on the strait shifting. Ithink mack is one of the best trucks around i just don't know about there trannys,but it could just be me to,kind of green on driving truck after 22 year delay.thanks again