[perseverance511]

I just recently bought a 90' Chevy Single cab, with a rebuilt 350, 305 heads, intake, cam, 4 barrel carb etc.
Also the standard trans was changed to a 700R4 with upgrades.

MY QUESTION IS THIS: seller described the rear end as being geared high. The truck is definately geared for stoplight to stoplight performance. But a friend told me today that this mean it was geared low. Which is correct? My father and I seemed to think that the larger the gear number (such as 4 11) meant geared high? Somebody please explain.

Is there any way to find out which gears i have exactly? this friend also told me of a trick by jacking the rear end up and turning the wheel one full rotation and then count how many times the drive shaft turns? Any validity to this?

Thanks for any insight...

[MI2600]

A "High" rear end is a low number, and vice versa.

[derm]

This is an arguement that will never end. Kinda like is it a 'soda' or a 'pop' or a 'coke'.

In my world, higher numerically is 'lower' gearing. ie: the 6.62:1 1st gear on my tranny is a Granny Low, and the 5.13's in my pumpkins are 'real low geared'. Thus, you double your gear reduction using your transfer case and shifting into 4WD 'Low' range.

Jack up one tire with the tranny in N. Assuming you have an open diff, you can mark the pinion position, rotate the tire 1 complete revolution, and get a rough estimate of the gear ratio from the # of turns the pinion makes.

Depending upon the rear end, it may be just as easy to pull the differential cover and count the teeth.

[poncho62]

One of the most misleading automotive terms..................

Depends whether you mean "high speed" or "high # of teeth" on the gear........and they amount to the opposite.

I have always stated it as the number of teeth....That doesnt change, but the speed does........So, a high geared rear has more teeth on the ring gear................But, thats just me.,,,,,,,,,What do I know, I cant even play a guitar.........

[jimfulco]

If you use the jack-up-one-wheel method, you need to turn the wheel TWO full turns for the ratio to match the turns of the driveshaft.

[pasadenahotrod]

Numerically high-geared differentials are 3.90:1. 4.11:1, 5.56:1.
Numerically low-geared differentials are 2.70:1. 3.08:1, 3.23:1.
Somewhere in the mid to high 3s lows become highs numerically speaking.

The opposite is true when speaking of bottom end speed or top end speed.
Top(high) speed differentials are the lower numbers. Here we're speaking of road course and land speed stuff.
Bottom end(low) speed differentials are the higher numbers. Here we're speaking of drag racing, any short course acceleration contests.

With an overdrive transmission you get a referee which gives you the best of both worlds.

[xntrik]

Do you start out in low gear and cruise in high gear?

Low gear gives more rpm, high gear gives less rpm.

Terminology has been that way for at least 6 decades.

If people are too stupid to realize that, don't become like them.

[shiftstick]

pasadenahotrod has the correct terminology. As for determining gear ratio pretty close you can do the following as others have sugested if you have an open diff you will have to rotate the wheel that is jacked up two complete turns and count how many turns the drive shaft has rotated ,IE: two turns on wheel = 3 and 1/2 turns on the drive shaft you will have a 3.50 gear set. The reason for two turns on the open diff is the differental or some times called spider gears. They have a two to one ratio and require two turns of the wheel to walk the ring gear around 1 revolution. If you jack up only 1 wheel with a locker, limited slip or spool you will not be able to turn the wheel thats jacked up with out the other wheel trying to move.

[Richard Ellis]

OK...Lets' throw in another term which I myself like to use & is not quite so confusing. "Tall" gearing ,which is regarded as a low numerical number, 2.55-3.08, freeway cruising. "Short" gearing, high number, 3.95-4.10, lotsa jump off the line, lousy for the freeway.
_________________________________________Rick..... ...........

[poncho62]

Originally Posted by Richard Ellis

OK...Lets' throw in another term which I myself like to use & is not quite so confusing. "Tall" gearing ,which is regarded as a low numerical number, 2.55-3.08, freeway cruising. "Short" gearing, high number, 3.95-4.10, lotsa jump off the line, lousy for the freeway.
_________________________________________Rick..... ...........

More confusing....................we called tall gears here as the 4.10s etc.

we didnt use the short term....just called the 2.73s etc...."highway gears"

[xntrik]

Originally Posted by xntrik

Do you start out in low gear and cruise in high gear?

Low gear gives more rpm, high gear gives less rpm.

Terminology has been that way for at least 6 decades.

If people are too stupid to realize that, don't become like them.

Ditto

[jimfulco]

Don't forget the "deep" gears.

[peteshotrodshop]

someone mentioned that it is determined by the number of teeth on the ring gear. actually this isnt true. it is determined by the difference between the number of teeth on the ring gear versus the number on the pinion. one example is GM 7.5 rears. as far as i know they all have 41 tooth ring gears. but a 4:10 has 10 tooth pinion, 3:73 has 11, 3:42 has 12, etc. dividing the number of teeth on the pinion into the number of teeth on the ring gear is the only real way to find out what gears are actually in the rear. over the years they could have been changed and therefore dont match a tag on the cover, or the option sticker in the glovebox. so unless the gearing in your truck is unsuitable for the use you intend for it, don't wory about it. of course if you just absolutely have to know. take off the cover and start counting. the old rear could use new lube and gasket anyway. as for the terminology about "tall" gears. its as stated by others. now how about "STEEP" gears, lol.