as u all no i got a new z28 that has been modded. but i got 2 things that i need to know and r driveing me up the wall. first i dont know if my stall converter is stock or has it been changed. also i got the same problem with my gears. i got know clue if they r still stock. and if these have not been upgraded i am sure it is robbing me of power( 83 gears have got to be crap). so my question is what do i do to find out what i got? oh and the dude the built this car died so just asking him aint gunna happen.

 

To be truly sure with gears the only way to find out is to look right at them. Changing your diff fluid would be a good idea anyway when you get a new car yer not sure about.

 

Yeap to find out your gears, remove the diff cover and have a look. there will be a ratio on the side of the ring gear.. you really have to look for it though as it is kinda small. But say you have 3:73 then it would read 11:41 for example. But Justin is right being that you just got this car you should have the gear lube changed anyway, just so you know it has been done recently. I presum it is posi?? If so make sure to go to GM and get some of the Posi/LSD additive to add with the gear oil. I ususally put the additive in first.

Now as for you stall, well that can be a bit harder to tell, unless it has like over a 3000 stall point. Does tha car seem to need a decent amount of RPM to get her moving, or does it basically just go?

 

To find out the torque converter stall speed,
Drive the car as slow as you can go in 2nd gear. MANUAL 2nd
Floor the *gas and brake* Hard at the same time.

Read the tach, the rpm reached, just before the trans downshifts
is your stall speed. Only valid if the tires do not spin.

To find out your rear gear ratio you'll have to do a simple driving test and some math.

Drive the car steady at 100KLM/HR (62.5 MPH) with the shifter in D.
3rd gear on a automatic or 4th on a manual trans.

Not in OD. Read the tach.

Measure the distance with a tape measure (in inches) from the ground
to the center of your rear wheels. Multiply this by 2.
This is your actual tire diameter. (in inches)

rear gear ratio = rpm / 62.5 x tire diameter / 336

Example 3311rpm / 62.5 x 26" diameter /336 = 4.10:1

 

.... from the ground to the center of the wheel

 

kool thanks for the info guys. F-BIRD'88>thanks for explaining it with details i am gunna try it later tonight when i go out. but anothing guy told me to do a burn out slowly and just before it spins what ever the RPMs r at it the stall point. i just tryed this and the first time it just started to spin at 1700 to 1800 PRMs then i tryed again but car started creep forword but did not spin>rpms went more higher, does that count. anyway i will try your method tonight.

 

brake stands wont be an accurate measurement as your rear brakes play too much of a variable.

 

I cant remember if u said your car was stick or auto but 83 had some good gearing, most are 3.73's or 3.23's for the z28's


https://www.thirdgen.org/newdesign/tech/techdb.shtml


Now this dont help if he changed your gears, but if there stock, they are at least not too bad

 

similar question, did any 85 z28 come with posi? Also what would the gear ratio be?

 

85 Z LG4 came w/3.23 for manuals and 3.08's for auto
85 Z LB9 came w/3.23's only

 

The easiest way to find out what gears you have in the rearend is to simply turn the REAR WHEEL and count howmany times the drivshaft turns. if you have 3.23 gears one rev of the rear wheel should turn the driveshaft 3.23 times. Only turning the rear wheel once and trying to determine whether the driveshaft turned 3.23, 3.08 or 3.73 times can be a little tough so I just turn the rear wheel ten times count the number of times the drive shaft turns and divide by ten.

example:

turn rear wheel____ drive shaft turns____Math____Gear ratio
10 times____________ 37.3 times____37.3/10_=_3.73 to 1
10 times_____________30.8 times___30.8/10_ =_ 3.08 to 1
10 times_____________27.3 times___27.3/10_ =_ 2.73 to 1
10 times_____________32.3 times___32.3/10_ =_ 3.23 to 1
etc. etc. etc.

Method

To do this I ususally jack the car up at the rear and support with jack stands. Put the transmission in neutral and rotate the the rear wheel by hand. Putting a chalk mark on the driveshaft and the wheel you are watching makes counting a lot easier. If your car has posi no other set up required however if it is an open rearend you need to stop one of the wheels from turning so the driveshaft will turn.

No big deal to do this at home with jackstands but if you happen to have your car in a shop and it is up on a hoist it is even easier.

ATB
Ric