My '89 9670 build


For you lovers of the Class 8's and bigger.

Golden Jubilee
Golden Jubilee

Posts: 5160

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Sun Jul 24, 2016 8:50 pm

Re: My '89 9670 build

I left a 3.73 center section in the rear hole. I don't think the axle would retain its strength with just a cover over it.
I packed the wheel bearings in grease and had some old half shafts that I cut off right behind the flange to seal In the grease.
The axle had oil in it and I found over the course of the time I ran it, that the oil made its way out to the hubs, so they had a mixture of grease and oil on the bearings.
Since I am now going to use the 3.73, all I had to do is change the rear hubs to spokes, and slide the correct half shaft in it.
Progress is slow. The high heat and humidity has limited the work I can get done.
I need to convert the Big Cam 1 to Big Cam 3 oiling and do the rods and mains before it gets cold in the late fall.
I'm sure there will be a million little things wrong from sitting ten years, I hope to have both cabovers plated, and I can switch the insurance back and forth as needed.
I just sent in a steering box to be re-manned, its nice to have two trucks that are more or less identical, and a 3rd I cut up for parts. Means if I need something rebuilt, more than likely I have one in the storage trailer I can send in, if it is not already useable in its present condition.

Golden Jubilee
Golden Jubilee

Posts: 5160

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Fri Aug 05, 2016 2:24 pm

Re: My '89 9670 build

Progress is slow, I got the steering box back, cost was over a grand. I would have waited until I need one, but the turnaround time was a month. Better to have it on hand, and be in no rush, then to not have it and have a truck down because of it.
We have been having dew points in the 80's, which makes outdoor work beastly. I haven't got much time to work on this truck, and the weather is setting me back even more.
Got the inter-axle drive shaft in, and the slip yoke has some wear, but I decided to run it and see if there is a problem, fixing it only if there is.
One of the problems, is the output on the trans is 1810 series joint and the input is 1710 on the powerdivider, The interaxle is 1610.
The logical place to make the conversion is in the jack shaft between the transmission and the slip yoke to the power divider. I could go 1810 all the way back, but besides being overkill, would require a new slip shaft and input yoke. Yokes of this size don't come cheap. Full retail Spicer I was looking at over $200 for the yoke behind the hanger bearing. I was able to cut that in half by reuseing the slinger, and going with an aftermarket yoke.
1610 is a little small by todays std, but considering it is only the interaxle shaft and shouldn't see full torque, it should be fine. It was what IHC used, so they felt it was OK.
1710 should be plenty stout enough for the 400hp Cummins and the 3.73 ratio.
The orignal set-up was 1810 but it was feeding 3.42 rears on low-pro tires. I'll be spinning it faster, so less low speed loading that requires the big shaft and joints.
With driveshafts I think going too big has as many drawbacks as too small. The added weight of the shaft and joint makes bearings wear quicker and means more rotating mass to control.
Once the new yoke arrives, I can do a mock-up of the truck in running height and get a measurement for cutting down the shaft I have. The RA-472's powerdivider sticks out the front of the axle further than the SQ100's that came in the truck, so the shaft it too long.

Golden Jubilee
Golden Jubilee

Posts: 5160

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Fri Aug 19, 2016 10:16 am

Re: My '89 9670 build

Got the new yoke installed on the jackshaft and got the measurement. Sent the driveshaft in and the report back was bad. The slip spud had excessive wear and the weld yoke had some cracks starting. Ended up with a new everything, yokes, tube and slip spline. A $600 driveshaft.
I guess it is too be expected when you do so much heavy-haul like I did with this truck. I just goes to show that the true cost of heavy haul doesn't always show in the short run, The rate may look good but it takes its toll on everything and the real cost may not show for years.
I beginning to see that the cost of this rebuild is going to be high. The truck has little or no value in it present state, and the cost to rebuild is low compared with replacing with another used truck, but it is doubtful that I will ever see the full value of the money put into the overhaul.
Dewpoints are back in the 70's with heat in the 90's so will be lucky to get the driveshaft hung and the air ride re-plumbed. It is depressing how slow the work goes. Soon I'll be fighting the cold and snow, I hope the truck is back together by then.

Golden Jubilee
Golden Jubilee

Posts: 8936

Joined: Thu Dec 27, 2012 12:45 pm

Location: Canada's left Coast

Post Fri Aug 19, 2016 10:48 am

Re: My '89 9670 build

I feel your pain Mister CB89. I had a friend who worked at Kenworth. He was really beat up when he retired. It is a tough trade that is made more difficult by the size of the components and the complicated design of everything .
I was visiting a local driveline shop. Their main customer base is highway tractor, heavy haul and off road logging trucks. I am thinking that $600 would be the cost of, "how can I help you?" on the really big stuff like the Pacific.
I would rather have tools I do not need than to need tools I do not have
Thinking risks being controversial and possibly being offensive

Golden Jubilee
Golden Jubilee

Posts: 5160

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Fri Aug 19, 2016 10:59 am

Re: My '89 9670 build

It really points out the need to carefully spec a truck. If I had 2 spd rears when I did the heavy work, the driveshaft would likely be ok. I went with 2spd rears when I had to rebuild the rears of my Marmon.
It is cheaper and easyer from a Mfg standpoint to use a 18 spd trans, but that places all the torque multiplication up front and requires the driveshaft to take it all. I did all my heavy-haul with a 13 trans and single spd rears.
I briefly considered 2 spd for this build, but the cost and the amount of time I will likely be in this truck, doesn't lend itself to that.

Golden Jubilee
Golden Jubilee

Posts: 5160

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Mon Sep 18, 2017 9:53 am

Re: My '89 9670 build

Wow, it has been over a year since I posted on this truck. I decided not to change the rods and mains. I did pull one set and found they had been changed around the turn of the century, but don't look like they saw much use.
I did convert to Big Cam 3 oiling and jakes.
There is a picture in the K section of me swinging the engine and trans.
Once installed it fired right off (less then a rev) and ran smooth and no smoke great oil pressure! Houston, we have a keeper!
Trans needed a new input shaft from doing heavy haul with a non-dampened disks. The disks were used because I kept breaking damper springs and the last thing you want is to loose the clutch under a heavy load. Going to non-dampened solved that problem, but I knew going in, that shaft wear would be the price.
Had a problem with a poorly machined replacement shaft and had to buy another from another mfg.
It is very satisfying to watch this truck come back to life after sitting for more than a decade.
Over the course of running the '83 I have located suppliers and part numbers for the more common problem pieces. One thing that has really changed since I took it off the road, is the expansion of the internet and parts suppliers. When I was last running it, everything came from the dealer, and that meant two trips to Omaha, one to order (almost nothing was stocked) and another to pick it up. Now most can be mail ordered over the .net.
I now need to get the driveline and air system working well enough to back this truck into the barn, so I can pick away at the small stuff as time allows. Unfortunately, this will mean the Marmon will have to sit outside. I am hoping to get the Marmon into a shop for a rear suspension swap in the near future. I have decided, that I am too old and too slow to do the work myself. The problem is finding someone to do the work to my satisfaction. A poorly done job can ruin the frame and make the truck worthless.
I am less and less sure of the date when I will drive it. There is so much little stuff that will only show up once it is moving on its own. I also need (want) to install an Espar heater system like my other trucks but that is fairly involved as I tie cab heat, engine heat, fuel heat all together in to one system. I use a 7 day timer and that requires more wiring to the cab, but gives diagnostic codes if there is a problem. I picked up 2 used Espars over the summer and re-ferb' ed them.
This Cabover has air start like the Marmon, and I want to install a remote reading Ammeter like the other two trucks have, and this requires some re-wiring of the main electrical feed. Better to do this kind of work slow and meticulous, than try and be fast.
My brother found me a good air tight wood stove for the barn, so I can have heat while I'm working on these things.
Un like the engine swap, most the remaining stuff can be picked-up or left off as work allows, once the truck is indoors.
In some ways the '89 is in much better shape than the '83 (mostly cosmetic) and in others worse. I had a fuel tank strap part just sitting in the yard! It will take a while to address all the little things.

Site Admin
Site Admin

Posts: 4938

Joined: Thu Nov 29, 2012 9:10 am

Location: Nampa, Idaho

Post Mon Sep 18, 2017 10:33 am

Re: My '89 9670 build

It is the curse as we get older, TIME. It is the blessing for those who are young, they think they have all they will need. As you say, just keep picking away at it. You already know the satisfaction of a job well done. You are also keeping the big trucks alive and giving hope to some who like them to give it a try to resurrect one.

Golden Jubilee
Golden Jubilee

Posts: 5160

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Tue Sep 19, 2017 7:42 pm

Re: My '89 9670 build

Spent yesterday designing and started building a new intake system from scratch. The NT88 I put in the little cabover could not use its stock air cleaner/intake system as it hit the thermostat housing. I needed to get the little cabover on the road ASAP, so robbed the air cleaner/ fresh air system from the Big Bunk.
I can not put the orignal little cabovers system on the big bunk do to the placements of the lift cyl mounts. These are much bigger on the longer BBC cabovers than the shorter BBC one. Move one thing and you effect 3-4 others. Some are easy to over come and some are not. I had to relocate the air cleaner above and to the rear of the turbo, then required some fair sturdy bracketry to be fab'd. This places the air cleaner 90 degs from how it was designed to be mounted, but should work. Next is to duct the cool air from the grill back to the inlet of the air cleaner. It will take some fittings (hoses) and some of the orignal ducting.
Today and for the next few days I am out earning a living so no pic's to show.

Golden Jubilee
Golden Jubilee

Posts: 5160

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Sun Sep 24, 2017 10:17 am

Re: My '89 9670 build

Repaired and re-routed the air line to the air suspension. When I last ran it, it was set up as a single drive with the back axle as a non-powered tag. This ment that the "powerdivider lock" controlled a dump on the back axle and the dump was plumed to the level valve on the front axle.
I moved the level valve to the rear (stock) position and had to re connect the air bags in sequence.
Now I was ready to move the truck under its own power for the 1st time in many years. It was a good feeling and I was surprised that the brakes were not rusted to the drums.
Now I can move it inside (where I have the option of HEAT in the cold weather), for the rest of the work.

Site Admin
Site Admin

Posts: 4938

Joined: Thu Nov 29, 2012 9:10 am

Location: Nampa, Idaho

Post Sun Sep 24, 2017 1:17 pm

Re: My '89 9670 build

Sounds like your well on your way to a fully functional truck again. Hope to see video in the spring?
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