eshack93

I understand that cost benefit. My thoughts were “well it may save money in the long run” but dumping 10 grand into a transmission swap isn’t really a practical solution either. Thanks for the input I’m gonna keep digging

Question for you fellas, I’ve got an tandem dump r model with a 283 Mack and a two stick 6 speed with 4.17 rears. The ol 6 speed is gonna be due some repair pretty quickly and I’m really considering pulling it and putting an 8LL in it. Be nice to have a couple more gears to traverse these hills where I’m at. My question is does anybody have the numbers or can point me in the right direction for the bell housing, clutch and driveshaft I’ll need? I’m assuming all those things would have to change. Thanks in advance

Okay fellas. Sorry it took so long. Cleaned the pump up and put it back on, filled with oil etc. drove it down the road and it’s got 80 psi at 2,000 now and 32 at idle. Can too much press hurt? Or is it just high cause of the fresh rebuild?

I’d love to see one. Want to make sure this pump is missing something or broken before I would order a new one ya know? Thanks for all yalls help!

Checked the pump for scratches it’s all pretty clean the teeth all look to be in good shape. I polished the pressure valve with 1500 grit sandpaper and got it baby smooth. My oil pan is 9 inches in the deep part of it towards the bell housing.

I’ve got a 79 rs686 with the 283. It has 3 oil filters. How would I tell if it has the oversized pan or not?

This trucks a 79. It’s always held about 9 gallons which is what it’s got in it. It’s full on the dipstick which hasn’t been changed or anything. What’s the proper oil amount for a 283 e6?

And what about this brass bushing inside this gear? Is it supposed to be one long piece? I’ve got one small piece and one big piece

Would the surface rust on this pressure valve on the oil pump itself be a problem? I also pulled some bearing particles out of those small holes. I’m not super confident in my knowledge of how this oil pump works and what this pressure valve thing is for

Well I double checked the gasket at that base of the filter housing and it’s definitely got the correct gasket. I was sorta hoping that was the problem. Gonna drop the pan again and double check the oil pump. Make sure nothings missing or out of whack on that. However I did notice when I pulled my oil filters off that they were only about 3/4 full. What would cause that?

Just looked through my service records. I replaced oil stand gasket approx 1000 miles before overhaul happened. Didn’t notice a drop in oil pressure after that gasket was replaced though. Coincidence? Or do you think they’re related?

I did the oil filter stand off but that was probably 10,000 miles before the rebuild. Didn’t have any oil pressure problems at the time but the number two rod bearing spun. Which caused the rebuild. Ordered the gasket for that oil filter stand off the vin and it only appeared to fit one way. What are the odds those two things are related?

Yessir I made sure to jack the crank up and did one bearing at a time. It’s all within spec. That’s why I’m Kindof having a mind explosion. I’ll check on that oil pump and get back with you. Maybe when I changed a gasket something fell out of place. Thanks!

Yeah I get that. I’ve worked on a lot of stuff but this trucks been a headache since day one. I was hoping the inframe would solve a lot of that. I tightened up a lot of oil leaks, air compressor, power steering, remachined heads, new valves, pistons, liners, all bearings, crank, clutch, radiator. Only thing I didn’t change was cam and oil pump. But yet I’ve got low oil pressure and I’m banging my head against the wall. Only thing I can think is that oil pump was on its way out. That pump is not timed is it? It’s driven off the air compressor gear which was not timed.

Joey I read through this post and went through a lot of the trouble shooting Mike did. I have checked the pressure valve on the oil filter housing and did not see an issue with it at all. The spring had a lot of pressure on it. Cleaned it put it back together. I changed the crankshaft when I did my inframe so the oil pump was off, the rebuild kit came with some o-rings and gaskets for the oil pump so I changed them. What are the odds something didn’t go back together correctly on that pump? I mean it was relatively simple just a couple bolts. But I definitely do not have the correct oil pressure now

Mike, Did you ever figure out your problem on this? I just did a rebuild on 2 valve e6 that has the exact same symptoms as yours. Oil pressure is great on startup but just drove it 10 miles and at an idle it’s already down to 15 psi and 60 psi at 2,000 rpm. Wondering what my issue is.

Preciate all yalls help and input. Got it buttoned up. And yes I fixed both rear main leak and transmission leak and cleaned it up good before I pushed it completely back together

That’s the specified distance according to the paperwork. 1/2-5/8”. Preciate the reply! I’ve done 10 tractor clutches since the last big truck. My brain was a little fuzzy on it.

I’m a little confused fellas. Been a long time since I done a clutch in a six speed. The truck is an RS686. I’m looking at this release fork and the way the cable works it seems completely backwards. If I push this back together with the fork on the transmission side of the throwout bearing then when I push the pedal it will actually pull the fork away from the bearing. So how would it engage it? First picture showing the fork. The paperwork is reading like the fork goes between the throwout bearing and the clutch pack, but if that’s the case then the fork would pull the bearing towards the transmission, how would that ever work? Second picture showing the bearing and my finger is pointing to a pad that the paperwork says to put the fork on.

Does anybody know what transmission can bolt up to an endt676 engine? Currently has a two stick 6 in it and I have to pull the tranny to change the crank. Thinking about swapping to a tranny with some more gears. These hills around here are rough on a six speed. Just looking for options. Thanks!

Definitely leaning towards the valves. Gonna pull the heads in the morning and send them off to be completely redone. I had the valves in adjustment and ran the engine, with the knock, and now the intake on number one and 4 are both loose. Gonna drop the pan and inspect the cam. I’ll let yall know tomorrow

i have not. guess that will be next on my list. i glanced at the camshaft but did not do a thorough check

Alright I’m at a loss here. Parked the truck because I heard a slight knock at higher rpm’s. Determined it to be fuel knock as 2 injectors were straight dumping fuel. Had them rebuilt, put a new air compressor, while I waited on the injectors, because the old one was tired. Ran the truck moving some dirt at the place just to see and once it got up to temp the knock came back but way harder. Pulled the pan, cylinder 2’s bearing was in bad shape. Full Inframed the truck as it’s been on my mind because the truck has had excessive blowby in my opinion for a month or two. Put it all back together yesterday and drove it this morning to “break it in” and no sooner did I get to the gate the hard knocking came back. New rods and mains, pistons, liners, rings, adjusted the valves, checked the heads for warpage. What am I missing here? All the valve springs, rocker arms, push rods appear to be just fine. The trucks is an rs686 with the two valve endt 676. ANY help is appreciated.

Paul nailed it right on the head. You get into thinking one thing and wind up getting another. Just like everyone else said, high mileage isn’t a huge deal if it’s been maintained reasonably. Whenever you go look or drive a truck just make sure you get it good and warm and keep an eye on oil temperatures and water temps. An older mack will hold together and if you learn to work on it then you’ll be alright. Just keep you some money set aside for repairs because there WILL be breakdowns. Whether the trucks got 5,000 miles or 5 million miles. It’ll work out like it’s supposed to

Just for curiosity sake, what oil are you guys running in older Mack trucks and why?