Gear Ratio & Me

[newman187]

I bought a Jeep Grand Cherokee (please no flames cuz i'm a noob when it comes to rock crawling), from what I know now and what i'm most concerned about is the gear ratio. According to the gentlemen I bought the Jeep from he put a Ford 9" 31 spline rear end and a Dana 44 30 spline up front, the jeep has a custom 4 link suspension with coil springs and Blisten shocks with resivoior. Any way he got the axels from the Junk yard and he does not know what the gear ratio is, there is a tag on the rear axel with a 3/50 or something like that, i'm assuming that the gears are 3.55, the front has no indication and he suspects its 3.55 as well. The truck itself has 35" tires, and according to some people the optimum gear's are 4.86, the truck itself runs and drives fine with the current gears (open axel's), long story short the truck punked built 4 runners all day long last Thanksgiving (before I bought the truck). I guess I just want to know are the gears ok, or should I spring for the 4.86 and throw lockers in there as well? I'm tight on money right now so droping a few grand just isn't going to happen.

Also whats the easiest way of determing the gear's without cracking the cases?

 

[Spork]

Get a buddy make a mark on the driveline and one on the tire slowly roll the truck forward one tire rotation and count the number of times the driveshaft turns.
4 and a half turns of the driveshaft ~ 4.56
3 and 3/4 turns of the driveshaft ~ 3.73
etc.

 

[notajeep]

3.55 seems an odd ratio for a stock junk yard 44. but you never know I guess.

 

[Kiel]

3.55 seems an odd ratio for a stock junk yard 44. but you never know I guess.

Thats what I thought when both my waggys came with 3.54's. Usually the trucks have a steeper gear ratio but I'm guessing your came out of a fullsize bronco or something so it is very likely. I would change gears if you were planning on locking it, but if money is tight and you know you will change it later anyway. I would weld them and go till you break, that is if you trailer it

 

[Tacoma]

aren't all Dana R/P's stamped with the tooth counts????

 

[Meat_]

3.55ish isn't uncomon if it had a stick

aren't all Dana R/P's stamped with the tooth counts????

He doesn't want to open the diff

 

[Tacoma]

Man, my Skim Speed is set too high tonight. Oops!

 

[newman187]

I'll try and find out what the axel's came out of and maybe that will help me figure out the ratio. I am going to Moab this Easter but wont have the money to gear the truck untill the summer at the earliest but I still want to be able to lock at least the rear end. I'm going to buy the lockers and install them with my mechanic buddy in the next few weeks so we'll be able to figure out which gears are in the axel's.

Last night I was under the truck and saw no indication on the D44 what the gear ratio was, is there a specific place it might be stamped?

 

[newman187]

So I found more info out about the axle's, they cam out of a 76-77 Ford f100 or F150 and possibly a Ranger, front axle is a 30 spline Dana 44 high pinion, the rear axle is a 31 spline for 9".

as stated above the tag on the rear says 3/50 or something, any thoughts or any one know what the stock gear ratios are on these axles?

thank you