4.88 Vs 5.13

A

armygrouse

New member
Right now I'm looking at upgrading my axles from Dana 44s to Dana 60s and I'm just wondering what gearing I should go with.

The reason why I asked is because I haven't seen any calculators/charts that account for the automatic overdrives. I have a Chevy 350 with an 700r4 that I plan on hooking a blackbox and Ford NP205 up to. I also know that I'd like to keep my shoe size between 35 and 40, probably 37 or 38, and I'm looking at getting a front high pinion Dana 60.

I've looked around enough to know that either the 4.88 or 5.13 would be close to what I'd want, but I have no idea what the advantages or disadvantages of either are.
 
Also, I forgot to add that I plan on driving this to trails, even though its a dedicated rig. . . Which means that every few months it'll travel around 250 miles going from one set of trails to another, so I'd like to have good gas mileagle.
 
Thanks for the heads up

reason why I was asking though is because from what I found online people were asking with Dana 44s or less, and I didn't see much accounting for the overdrive and automatic that the 700r4 provides. . .
 
Before you can zero in on axle ratios you need all of the details..

Assume a basically stock 350? Peak torque about 2400-2800, hp around 4500- 4800rpm?

700r4 od ratio .70-1
assuming the above is true..

38" tires, .4.88 gears and .70od @ 65mph you're turning 1960rpm.

With one down shift to 3rd @ 1-1 you're turning 2800 + tc slippage could be 3000 @ wot.

I'd say this is puuurrrrfect.

Save the 5.13 for bigger tires
 
Last edited:
Robert kenney said:
before you can zero in on axle ratios you need all of the details..

Assume a basically stock 350? Peak torque about 2400-2800, hp around 4500- 4800rpm?
Click to expand...

Well I'm still setting up all the details. . . I just got a comp 4x4 cam for the Chevy 350 with an rpm range from 600-4600

comp cams cl12-231-2 - comp cams xtreme energy 4x4 cam and lifter kits - overview - summitracing.com

Right now my project rig is on hold, because I unfortunately lost my source of income. . .
 
I just went through this same decision with a similar rig I'm building (68 stretch Bronco w/ 203/205 doubler). I chose 4.88s to run w/ 40" tires (plus or minus). I'll be driving to the trails most likely but also have the low gearing of a 6.69:1 granny low 1st gear in the np-435 x the doublers giving me about 127:1 crawl ratio. With the 2.72:1 in that black box x 1.96:1 in your 205 you can stand to run a more "streetable" gearset in your diffs as you've got the low gearing in your xfercases to climb most anything on the trail.

I like this calculator:
gear ratio calculator
 
armygrouse said:
well I'm still setting up all the details. . . I just got a comp 4x4 cam for the Chevy 350 with an rpm range from 600-4600

comp cams cl12-231-2 - comp cams xtreme energy 4x4 cam and lifter kits - overview - summitracing.com

Right now my project rig is on hold, because I unfortunately lost my source of income. . .[/quote ]

good cam choice . I stand by what I wrote earlier . 4.88 with your 37" tires and the .70 od nice cruise rpm and one ds (3rd) to the sweet spot.
Click to expand...
 
Robert kenney said:
good cam choice. I stand by what I wrote earlier. 4.88 with your 37" tires and the .70 od nice cruise rpm and one ds (3rd) to the sweet spot.
Click to expand...

Well I agree with your recommendation of gearing. I happened to just get a front high pinion Dana 60, and a high steer kit. I also got a rear dodge Dana 60. I just figured I'd post the update on the engine because the cam might make a difference in gearing. . .

Unfortunately I have no source of funds right now, so I won't be able to get project terror running as soon as I would have liked . . .
 
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