MY 1969 PETE ON YOUR STEPDECK? SHOT IN THE DARK!!

I have a 1986 international eagle and have no issues with insurance for working it but your Pete is almost two decades older.

 

Wow, I can't believe how cheap you got it. That's cheaper than just liability on a beater car.

 

Glad to read you were able to get her insured.. Now you won't be running "outlaw" lol

 

Now we need to get the History Channel to film your rebuild....

 

That called getting sponsors lol.
You get the show and then you start selling T Shirts bobble heads and coffee mugs....

 

Should be a metal tag on the side. My bet is a 8341C. Spicer of course

 

No front brakes, 100% legal for the year.

The housing on the nose of the pumpkin in the photos from a few pages back is your power-divider. Those are definitely Rockwell's, SS's, SQ's, or SL's, my guess is SQ's, as these were the most common rears of the Rockwell line-up from that time period. The auxiliary looks like it may actually be a single-countershaft auxiliary (would be pretty late in the game for a '69 to have a single-countershaft, but, they were still around to some degree-ish, they were pretty much the only thing in the '50s and earlier). Driveshafts look standard, I'd assume 1210 (1200lb.ft. rated)

If it's a single-countershaft brownie, it is certainly an older auxiliary that's sitting behind the 13-speed (this truck is looking more and more like a backyard/ scrapyard special. Nothing wrong with that, trucks used to be built with the ability to swap, interchange, and rebuild as necessary). In modern transmissions (excluding Mack, more on this in a bit), virtually any Eaton or Meritor (what became Spicer transmissions in the 90s) is a dual-countershaft design, meaning, aside from the input/ output shaft, there's two shafts carrying gears, as well in the transmission. The ratio of the given gear is determined by the ratio of the gears engage between the input shaft and countershaft(s). Prior to twin-countershaft transmissions, the common design was a single-countershaft design, meaning that you had your input shaft and the countershaft creating the ratios (plenty of car transmissions have worked this way). The advent of the twin countershaft transmission was to handle increased torque-loads, as the torque load is split between two countershafts rather than one and the input shaft. Mack utilizes a triple-countershaft design, meaning the torque-load is split even further. This is why Mack transmissions are immensely tough boxes, it's also part of why the engine seems to fall off and shift a little slower, as there's more weight (intertia) slinging around in the transmission.

Aside from the fact that things were obviously changed and swapped around here and there, the truck was built to be fairly lightweight when it rolled off the line. The frame is aluminum, single-fuel tank, single air-cleaner, single stack, and a 2-stroke Detroit (that engine is several hundred pounds lighter than a 335 of the same era), not to mention most of the cab and hood assembly is aluminum. Full of fuel, ready to go down the road, she wouldn't weigh in past 16,500lbs, my guess would be as low as the high 15,000s in original form (lighter mainbox).

Regarding driveshaft speed, it's determined by the final drive ratio, i.e. the ratio of the "highest" gear in the transmission, the rear-end ratio determines the ultimate road-speed. Think of it this way: Imagine just the driveshaft is sticking out the back of the transmission not hooked up to the rears.

In a direct (1:1) gear, at 2100rpm, the driveshaft will be spinning at 2100rpm when the engine is turning 2100rpm. In an overdrive (less than 1:1 ratio) gear, as the output gear turns more than once for every rotation for the input gear, the driveshaft will spin at 2100rpm multiplied by the overdrive ratio. For example, a modern 13 or 18-speed has an 0.73 final (OD) ratio, so, driveshaft speed at 2100rpm equals 2100rpm x 0.73:1, or, a bit more clearly, 2100rpm x (1/0.73), which is 2100rpm x 1.369863 = 2876rpm, approximately.

Assuming his overdrive ratio in double-over is roughly similar to mine (0.67), the driveshaft speed at 2100rpm in double-over is: 2100rpm x (1/0.67) = 2100rpm x 1.4925 = 3134rpm. Difference is, my boxes are both dual-countershaft, bigger bearings, and dual-wall 1410 driveshafts, in short, they're designed to handle higher speeds and bigger torque loads.

That's why a vehicle with a lower rear-end ratio can achieve the same speed as a vehicle with higher rear gears with a wider overdrive gear, as the transmission will be able to rotate the driveshaft more times with the wider overdrive gear to counter the lower rear gears.

If the SQ's aren't tagged, to determine your rear end ratio, get the back of the truck on jacks and place a chock in front of the steers. If the truck won't start or you want to hold off on starting, back-charge the air-system and release the brakes. Get a soap-stone, mark a "top-dead-center" line on the tire, and then mark lines on the circumference of the shaft in 1/4s. Have a friend watch the tire as you spin the driveshaft, have the friend stop you when the tire returns to top-dead-center, meanwhile, count the revolutions of the driveshaft for one revolution of the tires. If it's just under 4 times, they're 3.90s, just over 4 times, 4.11s, about 4-1/3 times are 4.31s, just under 4-1/2 times are 4.44s, just over 4-1/2 times are 4.56s. The age of the truck, assuming the gears are original, rears will likely fall between 3.90-5.29.

Truckdad's advice is well heeded.

If the linkages are a little tight or sticky on the aux, get some chain lube and spray the linkages at the box and under the cab.

By the way, the proper term for the small driveshaft between the pumpkins is the "jackshaft", same term for the small driveshaft between the 13-speed and auxiliary.

Fun fact, just because I like being a smart-### and a gadfly, actually, you can have different ratios between the front and rear drive axles. This is never done at the factory, but, it can be done. Because the rears aren't solid drive axles, i.e., they can slip, the rears can make up a small difference between each other. Something like 3.55s up front and 3.90s out back wouldn't work, but, 3.70s and 3.73s, MAYBE 3.42s and 3.55s would feasibly spin. Bet your tire wear would look like hell.

What would not want to do, in any circumstance, whatsoever, if you had different ratios, is lock the power-divider. That would become catastrophic.

Regarding multi-speed axles, Eaton's are easier than anything to spot, as they have the distinctive rib on the back. Haven't yet seen a Rockwell rear with a rib, but, they did make 2-speeds.


This photo shows the rather distinctive rib found on Eaton 2-speeds.