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5 minutes ago, Maxidyne said:

The Fuller is an inferior transmission, stick with Mack. Besides, the Fuller will need different mounts and driveshaft. Unless the components are worn out, stick with stock and change as little as possible. Changing to a different ratio in the Rockwell rears may make sense though, not so much to get more speed but to get the cruising RPMs down which will really help your cruising MPG. IIRC, they offered 3.90, 3.70, and 3.55 ratios in that R170 rear end.

I would agree just a rear change would be easier, if he can find a desired ratio, but a fuller trans would be fine on a hobby truck.    terry:MackLogo:

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If he can find a whole assembly with the desired ratio that's the easiest swap, a lot of big carriers used R170s with 3.70 gears. Another option staying within the Mack family would be the 5 speed plus overdrive version of the 1000 series Maxitorque, though that would require a shorter driveshaft.

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We're talking about 40 to 50 year old transmissions, not the current models. It's hard to beat Eaton for value per dollar, and as you and many have noted here Mack drivetrain quality and reliability have declined since the Volvo takeover. If I were buying a Mack today I'd probably spec an Eaton transmission.

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If he can find a whole assembly with the desired ratio that's the easiest swap, a lot of big carriers used R170s with 3.70 gears. Another option staying within the Mack family would be the 5 speed plus overdrive version of the 1000 series Maxitorque, though that would require a shorter driveshaft.


The 2070 is the 5 speed overdrive with two low gears

Is there a difference between the 1000 and 2000 series transmissions

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IIRC a 2070 has a .60 overdrive top gear, definitely would cut your cruising RPM down!

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Given you have a 675, I would change the ratio in your R170 from 4.33 to 4.11.

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Mack initially allowed ratios as low as 3.90 on 20/22.5 tires until UPS persuaded them to offer 3.70.

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Mack initially allowed ratios as low as 3.90 on 20/22.5 tires until UPS persuaded them to offer 3.70.


Any idea how much weight ups was hauling with 3.70?

Were they on std. height 20/22.5's?

What engine and trans combo where they using?

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Was back in the late 60s, so standard height 20/22.5 tires.In most cases weight was around 40-50k pounds, but UPS tractors sometimes pulled Turnpike doubles and triples that got up to 70k pounds or more. Engines were the 237 horsepower Maxidynes and transmission was the wide ratio 5 speed Maxitorque, though initially they used a Spicer wet clutch but they were later retrofitted with a conventional dry clutch.

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The shifter on my 5 speed trans is real sloppy.

I have looked in the manuals but can't seem to find and information on the actual shift tower.

Is there a bushing that wears out?

What should I check when I remove the shift tower?

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