mack88
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Everything posted by mack88
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Yes it is a RD688S.
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I was told to use 80-90 gear oil only.thanks
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thanks for the ifo. Rob it will be great help.
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I did change it last summer at that time it did look clean on the inside.So i was thinking it should still be okay.Iv'e run about 275 hours since then.But i guess for what it costs i should try anuther one.
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my 12speed does not want shift when it starts to get colder.I was wondering how hard it is to rebuild the pisotn under the cab.Do i have to lift the back of the cab or drop the tranny thanks.
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thanks for your help. The one they put in first had a hinge with a roll pin,And i don't think they put any grease on it.
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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?
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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
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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.
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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.
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thanks for your help i will disable it and go from there
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i will post some tomorrow i am on dial up so it takes awhile to post pictuers
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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.
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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.
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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.
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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
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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.
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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.
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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
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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.
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thanks for that link,like i said great site.o by the way i am from up in canada,Saskatchewan.
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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
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mack88
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