Roscoetaggart

On 10/12/2019 at 12:35 AM, alex g said:

Have to measure diameter of tanks unless you plan on changing straps. If your looking for anything ask here in parts wanted you'll likely find it here.

Do you think the j bracket that holds the tank wouldn't fit if the tank was a different diameter, not just the strap? I am assuming both trucks would utilise the same tanks as the ch is the predecessor of the r model.

hi guys

In the process of restoring my r model currently, I am after two alloy round fuel tanks and have found two that are off an early ch in good condition, will these tanks fit my r model? 

Cheers

5 hours ago, mrsmackpaul said:

The smaller gears have dits cast into them

Larger gears have holes cast into them 

 

They are  very simple to work on, or at least I  have found so

Yes there is lots of parts and timing etc 

But if you have to force any gears in they arent lined up, they just drop in when all lined up

The hardest put is splitting them and linig them back up when putting the sections back together

A friend to steady the box sections and a tape measure to ensure its lined up square will help a lot

I have done them on my own several times

 

A car engine hoist is pretty helpful and once it's on its end is all you need

Paul

Thanks, so your saying that the 3 shafts within the auxiliary box at the back of the main box do have to be in the correct timing on reassembly? On a side note, does my gearbox have a clutch brake? It certainly feels like it needs one... I am assuming it would normally be on the input shaft but there is nothing I can see that resembles one. 

13 hours ago, mrsmackpaul said:

Could be lots of things

If you have the box out at the moment then I would lift it apart and have a look as its a much bigger job to pull it out later

You need to stand the transmission on its bellhousing and lift it apart with a chain block

The air split section is the rear section and once this is off it comes abart pretty simply 

The sliding dogs in there collect all the rubbish as in silicon dirt and what ever else you can think of that may be getting pumped around in the oil

Make sure the dogs dont have bad bevels worn on them or very rounded corners  as this can cause the dog not to slide in 

 

The 10 and 12 speed maxi torques I know of have no synchros at all, however I do know later model Mack boxes do have synchros

Im not enough of a expert to advise on later model boxes as I have never touched one , just old rubbish for me

 

Paul 

Thanks very much for your help, you certainly know more than me! I agree with sorting everything I can find while the box is out. 

I was just wondering as someone said the gears need to be all timed together on reassembly so I thought I had better check! 

Hi guys,

My r model has the 10 speed box in it, and it tends to grind somewhat excessively (more than I think it should) when switching between direct and overdrive. I have never played with a truck gearbox but there is a handy YouTube video demonstrating auxiliary box removal that shows the process. Our local dealer mentioned a while back that some mack boxes are synchorised and if not assembled correctly can cause somewhat catastrophic problems. Is this something I should be attempting myself? Is it likely my 10 speed box on my 1983 688 needs to be synchro? What is likely to be the problem? Gearbox is already removed during truck restoration so easy to work on. I would call myself mechanically minded to the point where I have reconditioned quite a few motors in my time, just never a truck gearbox. Thanks in advance 

On 7/26/2019 at 3:35 PM, Superdog said:

the 3208 was a factory option in the R400 series,model R492,same hood length,just lower GVW

Thanks for that,  I'm guessing it doesnt bolt straight up to a mack 10 speed but definitely tempted to go that way.

Hi guys, 

Just got my hands on a 3208 cat v8 motor, it was cheap so I bought it,  has anyone ever tried to put one in an r600 mack? Does it fit? Cheers 

Hi guys,

I am in the process of restoring a 1983 R model mack. I have the chassis completely stripped, we have split the chassis rails and sandblasted everything and we are now in the rebuild phase. 

My original air tank mounts (there are 4 tanks) were horrible looking bits of angle iron bolted to the outside of the chassis that looked very second rate. I can mount the two smaller tanks inside the chassis rails, but am looking for a way to mount the bottom two larger tanks in a way that looks tidy. Does anyone have any ideas on how to do this? It is a 688rst long wheelbase tipper and air start.

Sorry for the late reply guys, turns out the little air ram that actuated the fuel shut off was jammed and have ended up having to replace it. The way I worked it out was I disconnected everything from the fuel cut mechanism and when I put it in the right place the truck started fine and narrowed it down. Thanks for your help on this.

I have checked the fuel shut off again and it is spring loaded in what I would assume is the 'open' position, with an air ram to shut it off. I'll take the spring off and try it in the other position and let you know the results, thanks guys

Hi there, 

I have a 1983 R688 with the E6 350 motor in it, motor has had top and bottom end rebuild 5 years ago and runs very well but a couple of days ago it wouldn't fire up up me.

It turned over on me fine but it was as though fuel wasnt getting to the I injectors. I started the fuel bleeding process (which is a hell of a job when the truck is air start and you have a small compressor) and I wasnt able to get fuel past the injector pump. I got to the point where I cracked off all the fuel lines heading to the injectors and when I try and prime or crank the motor, the pump doesnt send anything out the top. 

My guess is that I havent bled it properly, but am well aware these pumps were not renowned for their reliability. Any help would be appreciated.

-plenty of fuel at the injector pump from the tank

-engine cranks and will run on ether or brake clean briefly so I presume timing drive is fine

-Fuel shut off seems to be in the right place (i think)

Pics of the injector pump attached if someone could let me know more about the pump as it has been painted over so the tag on it is near impossible to read.

Cheers.

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