rear end?

[Gearheadcurt]

ok I bought the truck, and come to realize that going down the road I am screaming everywhere

 

what are my options when it comes to final drive ratios?

[Jayden71]

Lots. 79s had 4.11s the 720s had all kind of different ratios. I turn bout 3900 or so @ 60mph in my 521. Its what they were built to do

[moparvwfreak]

my 73 turns 4k rpm at 60. thats just the way they are. as stated above, the 79s had diffedrent gears and 720s had an even better selection of em.

[Gearheadcurt]

Damn, cause that absolutely rapes gas mileage

What gears can be draped in to our rear end?

[datzenmike]

If it's the 77 in you profile it will have 4.375s in it which are fine for carrying loads, after all it is a truck. If primarily for transportation these can be swapped for 4.11s or even 3.889s. A 3.70 would work too.

 

Only the '79 4 or 5 speed 620 had 4.11s in them. The '81 720 long box automatic did also. (I have that set in my 620 now) There are many ratios to choose from in the 720 all the way down to a ridiculous 3.364!! It's too complicated to list then all so if you find one look on the inner pass side fender under the hood hinge. There is a little metal engine tag with the rear end ID and ratio stamped on it.

 

 

Bottom left says TRANS.AXLE go over to far right HF38. HF is the diff you want (not CA) 38 is the 3.889 ratio, 41 would be 4.11, 43 would be 4.375 and so on. AVOID 4X4s stick to 2wds, early is better..

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