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Overdrive was available in L model Mack trans. like a TR 150 with a .77 over in a 5 spd. A TRD 150 was a 10 spd. also with a .77 over.

Oldest I have is a '48 LJ with the TRD150.Those old ones had a weird shift pattern on the main box,.first was clear over to the right and up,2nd was to the far left and up,3rd straight down,4th to the center and back,5th(OD) straight up to the dash.Reverse was straight down from 1st.

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I don't remember the model number,only ever seen one in person,but it was a 5 speed main box with reverse,and it had a second stick that was only shifted in 5th gear,it was for overdrive.There was another with the same set up only the 2nd stick was for use with 1st and reverse only,it predated the more common version of the 2 stick 6 speeds,I've seen 2 of these in person.

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I don't remember the model number,only ever seen one in person,but it was a 5 speed main box with reverse,and it had a second stick that was only shifted in 5th gear,it was for overdrive.There was another with the same set up only the 2nd stick was for use with 1st and reverse only,it predated the more common version of the 2 stick 6 speeds,I've seen 2 of these in person.

Mike would that be a TRDXL1071 Direct and a TRDXL1070 Overdrive? Terry

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There was a guy in madison, He claimed to have a Mack 15spd double Over Drive. Said 5th in his main was over drive and 3rd in his auxy was over drive. He drove B61 tandem, It had SWB, huge axles and tires !

Claimed his main box had .85:1 5th gear and a .85:1 3rd gear in his spliter.

Is that even a possible combo ? ! Than if so wouldn't you need a Maxidyne to make it work out right ? ! Or would a Thermodyne handle the twin Over Drives ? !

Mike

1953 REO M48.

1962 GMC 3000.

1969 AMC AMX-390.

1983 AMC Eagle SX/4.

1988 AMC Jeep Comanche.

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Startability and top speed would be a function of rear axle ratrio and tire size. I have a B81SX with 8.27 rears, 24:00 tires and a Q box with two gears above direct

and it motors right along with a 180 hp motor. Had a R model once with a 13 speed triplex and 4:26 rears on 20:00 rubber and it would go 100 miles a hour if you could launch it.

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Well .85:1 is a 15% OD so dual OD's would of gave him 30% or .70:1 in 15th gear. The fact he said it ran 65mph at 2000rpm and the large tires looked to be about 12.00-24 so he'd of had to be running a 6.3 to 6.4 axle ratio to net 65mph@2000rpm with .70 OD.

But I'm just guessing, Also claimed it was 711 diesel but I heard a turbo when he headed on down the road.

Mike

1953 REO M48.

1962 GMC 3000.

1969 AMC AMX-390.

1983 AMC Eagle SX/4.

1988 AMC Jeep Comanche.

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I only seen the truck in passing after that maybe 5 or 6 times.

So I can't really say as what it all was for sure. Tombstone radiator not the big wide job.

My guess was about a 1950s model anyway, Without finding the truck again its not likely we will ever find out just what it was.

Mike

1953 REO M48.

1962 GMC 3000.

1969 AMC AMX-390.

1983 AMC Eagle SX/4.

1988 AMC Jeep Comanche.

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