Want to build a 1977 K125 as my new truck

Got a 2013 DAF which has way to many Paccar parts that attract way to much Paccar tax. Its also up for a engine rebuild at 60-80k AU, and the ZF auto management which is linked to the brakes is demanding attention. Then on top of that as much as I replace parts with my donor truck, another issue seems to pop
up. So its got me thinking about reliability, costs of repair, and what's needed for the next 10 years or 1 million km.

I hall 42.5T off a mountain with narrow winding roads that are not in smooth condition and can see 16% incline. So a cab over has merit for corners, especially one with the steers as forwards as a K series.

I have thought about buying a new truck but it puts me more in the control of companies. I'd rather distance myself from that and telematics technology that comes with it as far as I can. I am an owner driver and emission restrictions don't exist where I live.

So has me thinking of a 1977 K100 (K125 Aus spec) Kenworth with a 12.7lt Detroit 60 series 430hp DDEC11 powerplant. I don't think that motor is original but that doesn't matter as I would like to rebuild it. Can anyone tell me the pros and cons of a 1987–1992 DDEC II motor.

I'm also a lazy driver, no gears for me. I've had an Allison 6 speed auto, like proper auto, in another truck in the past. It seemed bullet proof compared to this automated manual stuff driven by actuators, modulators, and ECUs. I think to cope with the load and incline a retarder would be a practical addition. . Again like to hear pros and cons to the idea.

Of course it would be good to convert it to a fully air sprung cab. I half though or removing the system from the daf and see if it can be retrofitted, or something from a 200 series? . Something fully floating but also hinges. Any ideas on such kits be welcomed.

I do like the simplicity or Airglide or Hendrickson suspension, but it doesn't get much simpler than the old torsion bar. Would love to hear experiences of set ups on poor roads. Think an upgrade of the steer suspension would be a must, the ol cab over rides like its sits on the chassis, because it probably does.

Any I'm making enquiries into one I've had my eye on for a while. Reckon it can be done?

 

Thanks, so what RPM do you feel the power band works best.

 

Seems some of the reasons for the need is becoming apparent. Of course the Detroit is not responding so assume the add is dead. But there are Cummins 350, 400 big cams, and 409 options available, with 9 and 15 speed RR boxes. Perhaps if they don't pair with an Alison I should learn to drive clutch less haha. I'm not a fan of Cummins but given the motor is so old I don't have to deal with Cummins so to speak. Also from a quick google hunt the 309 is garbage so will leave the V8 alone. Its no surprise to me, or perhaps googles AI has it wrong, but the economy of these late 70s 350 and 400s is similar to my Paccar motor some 33 years newer. I half suspect any advances in economy are chewed up with emission control. Certainly not to drop 4k every 2 years on NOK sensors for the DPF won't be missed.

 

There is a nice and very well kept one with a Cummins VT903 V8 with a 15 spd RR that is fitting the bill. Its looking like for the 1977-80 era they all have 6 rod suspension, so it will be going. If I google Detroit Diesel engines Australia there is not that much comes up. That may not mean much just I'm not finding the path ways. Cummins however does seems a better choice in Australia unfortunately.

According to AI, a Cummins 460-485hp N14 red top mated with an Alison 4700 series with retarder, and some Mack Z bar suspension with Meritor 46-160P diffs at 4.63 ratio is a sweet match up for a 42.5T hi way runner or undulating / hill descending build. Given I have the opportunity to make this thing as simple and reliable as desired for the next 10 years, the above is where I'm currently at. I do think though if I can find one with a 350 or 400 big cam that will do. I'll learn to drive a manual. Its also simpler than the electronic red top so still may go that way regardless.

From experience in the daf the air glide suffers badly from failed torque rod bushes, like every 6 months from my application of heavy hill descending with twists and turns. Plus I've replaced all 8 bags and had 3 fail, but Paccar just give you a poker face look of so what. The Z bar I had in a Mack Metro-Liner is simple and also common. According to AI the Z bar will act as a torque brace for the auto while descending, and for all the twisting and turning I did for 3 years in the metroliner amounted to nothing. Plus I can get a cut off end Z bar suspension, with common diffs and coolers with desired ratios all in one all for very little. Maybe with ABS

another one I have my eye on but his not responding 350 Big cam, 9sp RR.

 

Ok, I have evolved to a K100E, and very keen on this bad boy. Ticks every box with the exception of comfort. So.....I'd like to hear if parabolic springs, good shocks, 2 point cab air suspension, and a high quality suspension seat will match 4 point air ride cab suspension. Keep in mind this is not being used in smooth asphalt, rather lumpy bumpy type back roads.

Detroit 12.7, 470hp, 100 series air glide, 46/160 diffs.

 

Anyone have any experience with this Hendrickson Airtec front end. They suggest it improves ride by 30% over traditional 2 leaf spring packs.

 

That's the hope, but my gut tends to side with you. I'm no expert but reading between the lines even a drive bogy spring by air is not any better than springs when loaded. But the authorities have swolled the concept at the truth, whole truth, and nothing buy the truth. Might just be sinical.

I got sold on the 100e as AI said it had 4 point cab suspension, but then changed its mind after I got excited. The later K200 which is too expansive for my needs, has 4 point but its a complicated conversion which also needs engineering. In my current truck it has 2 parabolic springs of which one has broken in the past. I see the new model has 1, if that breaks its as simple as will it steer or go over the edge. My concern with the Hendrickson Airtec is it too has one spring. All a bit ballsy really.