What Is This "diff Ratio" Stuff All About?

[adenijisegun]

I wish somebody will explain this diff ratio and how I can get to know which one I have on my truck.

Also Ive so much written about trucks with 2 tranny or gear lever whichever one, but mine has just one that counts from 1-5 + reverse.

Is there any advantage of 2 gear lever over 1? I ve heard some guys saying 2 is better but could be confusing.

Thanks

[Freightrain]

Well, the "differential ratio" is the gear ratio in your rearend(s). Something like 3.90's or 4.62 or whatever. It's the ratio of input to output: meaning it takes 3.90 turns of the driveshaft to get 1 turn at the tires. Pretty simple.

As for what ratio you have? I see you have an R model Usually most are stamped somewhere around the "pumkin" or "chunk" (the part that bolts into the rear end housing).

Two stick trucks. The only reason was MORE GEARING. Back in the early days low powered motors needed alot of gears to get a load moving and since the technology was not around to make it automated(air controlled) you had to have two sticks and do it yourself. Once the air controlled tranny's came around the two stick trucks became obsolete. You could now have a transmission with one stick with 1 or 2 air controls on it that did the "split" shifting for you. Some guys are 'old school" and like their two stick trucks, alot of guys don't. It's all a matter of personal taste.

You mention your truck only has 5 speeds, that is because the motor doesn't need anymore to be able to do the job. The newer Mack motors have a lot wider rpm power band then the older ones did, thus you don't need alot of gears. Back in the 60's, the power band was 1500-2100, but with todays motors, it's 1100 to 2100. That extra 400 rpm makes alot of difference in the need for gears.