Gear Ratio/Rear End 70 GTX/how to tell what's in there?

[WISCOPAR]

OK. Per the original build sheet my car came with 3:54 gears. Now....I've never had a car with this gear before but I swear what's in the car is much lower. I've had 3:23's and 3:73's both behind 727 trannys. My GTX is a 4-speed.

The gears are low enough, that I don't dare run it down the interstate.

Is there a way to tell (short of tearing apart the differential) what gears are currently in the dana 60?

I'm convinced someone, at some point switched out the rear gears.

Any thoughts or ideas are appreciated.

Thanks,

Will

 

[badlite]

Jack it up turn rear wheels 1 turn, count turns of drive shaft, that is your ratio.

 

[moparsteve636]

The only other factory ratio was 4:10

 

[WISCOPAR]

Jack it up turn rear wheels 1 turn, count turns of drive shaft, that is your ratio.

OK Makes Sense I think. 1 complete revolution of the wheel = the gear ratio.

So, I'm still a bit confused. The driveshaft should turn 3.54 times if this is the correct factory installed gear ratio??

 

[hashmaker]

^ What they said, all though you don't have to tear it apart... just pull the cover off and look at the edge of the ring gear most say the ratio or have the pinion gear tooth count and the ring gear tooth count stamped in them. Divide the pinion into the ring gear and you have it. Or if the drive line turns a hair over 4 times for the one turn of the tires it is a 4:10, 3 and half turns will be a 3:54 etc. I have had a few 3:54 sets and they don't leave you afraid of the freeway.

 

[WISCOPAR]

OK. Thanks guys. I'm guessing somebody put a lower gear in. Next question, is swapping them out a huge job....or something to leave to a pro???

 

[Cranky]

If you don't know what you are doing, you can burn up a set of gears in no time. At a minimum, you can end up with whining gears. There's a lot of youtube video on setting up gears. Many set them up by trial and error going by the pattern the gears make using marking grease which is usually white or yellow. I use the dial indicator method. Either way, it's a pretty good job.

 

[WISCOPAR]

Thank you very much. BTW. Is this like the A body forum? When I hit 25 posts then I can begin to formally thank people?

I think I'll leave this to an expert. I'm not completely mechanically stupid, but I've learned over the years....it's better to pay a pro for some jobs.

 

[WISCOPAR]

OK. I checked the rear end. I have 3:54's for sure. Is it possible that the transmission has somehow been geared differently??

Maybe all this has to do with the tire size I chose on the rear end??? I don't have the size at my fingertips, but I know they are short and fat!!

 

[NJRR]

Nice GTX!!!!!

 

[Cranky]

Nice looking car!! As for the amount of posts you have to make before you can thank someone.....well, I have no idea And yes, short tires can make a gear seem lower. The auto trans is pretty much a set deal. There are different gear sets for 1st but don't think there's anything other than stock for 2nd and high gear is 1-1. High stall converters can result in more slippage depending on the rate of stall. How much rpm can you generate sitting still and on the gas? Doing that isn't the most accurate way to check but it'll give you some idea. Stock factory performance converters were around 2200-2400.

 

[69roadr]

sweet GTX! i've got 3:91 in my 69 RR and it's at about 3000 rpm at 70! not real freeway friendly

 

[WISCOPAR]

Nice looking car!! As for the amount of posts you have to make before you can thank someone.....well, I have no idea And yes, short tires can make a gear seem lower. The auto trans is pretty much a set deal. There are different gear sets for 1st but don't think there's anything other than stock for 2nd and high gear is 1-1. High stall converters can result in more slippage depending on the rate of stall. How much rpm can you generate sitting still and on the gas? Doing that isn't the most accurate way to check but it'll give you some idea. Stock factory performance converters were around 2200-2400.

If this is like A bodies only, when I hit 25 I graduated to the rank of member, from "junior member" at that point, I was able to thank, and my Avatar went live as well. Anyway....I'm not sure what you mean my total RPM's sitting and on the gas????? Again this is a 4 speed. At stand still I'm sure I could rev her til she blows...??? I'm sure that's not what you mean though.