Is there any way to figure out what the rear end gears are without taking it apart. I just bought a 84 berlinetta with a v8 and t tops. And was wondering if there was a way if not, I just might have to pull the cover off to change the oil.

 

pull the cover it isn't a lot of work to do

 

thanks I was just wondering.

 

If the original gears are still in your rear end than it's a 3.08.

 

Is the 3.08 a good rear? If not what would a good to put in it that is good all around? Im not looking for alot of speed I would like to get better take off.

 

I wouldn't waste the time or the money changing gears. Nothing up front to show any improvements in performance.

 

Q: How can I easily determine what rearend gear ratio I have?

A: Jack up the whole rear of the car. While turning the tire on full rotation, count the number of times the drive shaft turns. A chalk mark can be used as a reference point. If you have a posi rear, then the number of turns of the driveshaft (per single wheel rotation) is your gearing (i.e. 3.50 turns would be a 3.50 rear, or a 3.55 more likely).

If you have an open (non-posi) rear, then you must multiply the number of driveshaft turns by 2 to get the gearing (i.e. 1.5 turns would be a 3.0 rear [1.5 * 2 = 3.0], or a 3.08 more likely). The reason for multipling by 2 is that in an open differential, the planitary gears cause the driveshaft to rotate half as fast as in a posi if only one tire is being rotated. Therefore, you must multiply the drive-shaft turns by 2 to get an accurate ratio, otherwise you must rotate one tire then the other (and not multiply). When one tire is not moving, the planitary gears are "walking" around the differential housing in the opposite direction causing the drive-shaft to rotate slower than if the diff were "locked".


This is from the Tech Articles.

 

If your car is an automatic and has a tachometer, then take a ride..............

Drop the tranny into 'D' and cruise on the highway until you reach 70 MPH........ read the tachometer. It will reflect your rear end rear ratio. ( 3800 RPM = 3.08 gearing. )

I think most manual tranny cars need to be in 4th gear for that little trick to work !

You can spend $300-500 for gear swap (or better yet - a complete rear end ) to get a BIG difference in "take off". Try making an engine do that on $300-500 ! Replacing the entire exhaust with 3" pipes and headers would cost more than that and not give you the same feeling............... ( But it would sound real good ! ) Maybe if you then replaced the entire intake system with upgrade parts, but then you added another $300-500 to the cost to get the same effect when you mash on the gas !!!

Replacing your rear end gear will give you you the largest improvement for the dollar if what you are looking for is quick satisfaction in your "take off" ---> IMO. The benefits to this are the option to add Disk Brakes or POSI if the car is not already equiped for VERY little additional time or $$.

Give your local junkyards a call and see what they have !!!!!!

 

Right. But 3080 = 3.08 rear gears.

 

Thanks for all the cool tips and tricks. I think the rear is a 3.08 but going to check it out. Everything else on the car is original so i dont see why it wont be the same also. But still have to check.

 

It also depends on your tire diameter. There is an equation by some link on the homepage.

 

I can't believe I forgot to mention this, This is how I found out whats gears I had in my 10 bolt (couldn't find the RPO stamped on the Rear). I did the turn the disk and count the yoke turns, came between 3.25 & 3.5. I figured 3.42's but wanted to make sure.

If you are sure it's the origanal rear for that car and the gears have never been changed. Call your local Chevy delership/Parts department, give them the last 8 digits of your VIN. They can tell you your gear ratio, open/Limited slip,etc.

No bashing, I just did this a few days ago when I was selling the 10 bolt. IT WORKS!!! If everything is still Factory

 

IF you pull the cover and do a tooth count

Gear ratio Ring Pinion

2.73= 41-15
3.08= 40-13
3.23= 42-13
3.42= 41-12
3.73= 41-11
4.10= 41-10

 

whats the deal with the 3.23's having more teeth than the steeper gears? how does that affect their performance? i have a gta with 4.10s and want to swap some more highway friendly gears, but i was thinking 3.42s or 3.73s. probably going to keep the 2500 stall, i basically just use the car for driving around town, and like the snappy acceleration of the 4.10s, but once or twice i would like to take it back home which is about 1200 miles away. would 3.73's make a trip like that with a tranny cooler, in may or june without excessive wear on the engine or transmission? it has a 700r4

 

I would pick 3.42 based on the Engine (355ci) tranny (700R4) and stall converter (2500).

Just M/O.


A tranny cooler is a good idea for ANY tranny - but not required. And I'm sure a 1200 mile ride will put "excessive wear " on any engine or any Trasmission !

Do you want to set the car up for your once a year trip - or for everyday ???? That will help you decide on the 3.42 or the 3.73 !!

 

Do you have a lock up torque converter? If not, that would make a huge diference in your highway driving no matter what gear your using. Also, just try slowing down. I often take a 1000+ trip home to see family and often pass the old muscle cars obviously driving to some weekend show doing 55-60 on the freeway. This will add a few hours to your trip but you'll get much better gas mileage and strain your car less also. I've seen many big block, non lock-up 3 speed, 4.10 gear or lower crusing just fine on the highway so it is possible. I also believe that at 65mph 4.11 gears only rev 300-400 rpm higher than 3.73's. there was a calculator online that will tell you the exact rpm for any given speed assuming no torque converter slip but I am unable to find it again. I just remembering thinking that the 4.10's really wouldn't rev that much higher at all at highway speeds, especially with overdrive.

 

I found the calculator. It's under the equations tab. With stock size tires, the rpm dif at 70 mph between 3.73's and 4.10's is less than 300 rpm with a 4 speed with overdrive. And with the 4.10's you should only be at about 2600 rpm(with no driveline slip) at 70. Not a huge change in O.D.

 

he saied to put the tranny in "D" not "d with the circle around it" (OD) wich is a 1:1 gear ratio, it works, but you have to be at ~75-77mph for it to be accurate