Do I have 3.73s?

91LX-5.0 · Mar 10, 2004

Hey all,
I just recently bought a 91 Lx 5.0. It came with a few things like headers, and h-pipe. They also said it had 3.73 and a shift kit (B&M). At about 65 mph I was pulling 2k, does that sound right? Also is there anyway to tell if the shift kits installed. It hits hard on down shift and jumps off the line well, for an automatic. (Not an auto fan, never owned one either, any tips on helping me launch would be welcomed). So any other ideas on weather I have 3.73s would be much appreciated.

Thanks alot
Ben

dvs bullet · Mar 10, 2004

unless you want to take off the diff cover then you have to count the wheel rotations and drive shaft rotations. It's not extremely accurate but it will give you a good idea if the gears aren't stock. As for the rpm question, sorry I'm a stick man.

Black 93 Fox · Mar 10, 2004

dvs bullet said:
unless you want to take off the diff cover then you have to count the wheel rotations and drive shaft rotations. It's not extremely accurate but it will give you a good idea if the gears aren't stock. As for the rpm question, sorry I'm a stick man.

I am also a stick. Like he said jack up the rear and count how many times the drive shaft turns in ONE wheel rotation.

Black 93 Fox

huskerpower02 · Mar 10, 2004

91LX-5.0 said:
Hey all,
I just recently bought a 91 Lx 5.0. It came with a few things like headers, and h-pipe. They also said it had 3.73 and a shift kit (B&M). At about 65 mph I was pulling 2k, does that sound right? Also is there anyway to tell if the shift kits installed. It hits hard on down shift and jumps off the line well, for an automatic. (Not an auto fan, never owned one either, any tips on helping me launch would be welcomed). So any other ideas on weather I have 3.73s would be much appreciated.

Thanks alot
Ben

I turn 2k rpm's at 60 mph and i have an automatic. I know i dont have 3:73's Im almost 100% sure you dont have 3:73's

-Drew

WDT440 · Mar 10, 2004

Hope this will help you.
I am using standard tire size 16" rims

Transmission Ratios: AOD
1st: 2.40 2nd: 1.47 3rd: 1 4th: 0.67

Tire Diameter 1: 25.74 inches
Rear Gear Ratio 1:3.55:1
MPH
RPM 1st 2nd 3rd 4th
1000 9 14 21 31
1500 13 21 31 46
2000 17 28 41 62
2500 22 35 52 77
3000 26 42 62 93
3500 30 49 72 108
4000 35 56 83 124
4500 39 63 93 139
5000 43 70 104 155
5500 47 77 114 170
6000 52 85 124 185
6500 56 92 135 201
7000 60 99 145 216
7500 65 106 155 232
8000 69 113 166 247

Tire Diameter 2: 25.74 inches
Rear Gear Ratio 2: 3.73:1
MPH
RPM 1st 2nd 3rd 4th
1000 8 13 20 29
1500 12 20 30 44
2000 16 27 39 59
2500 21 34 49 74
3000 25 40 59 88
3500 29 47 69 103
4000 33 54 79 118
4500 37 60 89 132
5000 41 67 99 147
5500 45 74 108 162
6000 49 80 118 176
6500 53 87 128 191
7000 57 94 138 206
7500 62 101 148 221
8000 66 107 158 235

A real accurate way to determine your tire diameter is to draw a line on the bottom of your tire, then draw a line on the ground which lines up with the line you just drew on your tire. Then move the car until the car makes one full rotation of the tire and mark the ground where the line on the tire is at the bottom again. Now measure the length between the two lines and divide by pie (3.14) and you'll have your tire diameter to use on the calculator (don't forget to use inches). This is the preffered method to use in determining your actual tire diameter.

Try here to better understand.
http://smokemup.com/auto_math/mph_range2.php

FOOT2DFLOOR · Mar 10, 2004

I've got an auto and i turn 1700 rpms doing 75 mph. But i have a pissy little 2.73 gear that came stock in it. As far as launching harder, use the foot brake like your about to do a "break torque" burnout. Let the car tack-up untill it wants to push the car through the light, thats the best way I have found to do it.

91LX-5.0 · Mar 10, 2004

???

So I am confused, you guys are saying its pretty sure i don't have 3.73s? Well are the hard to install, and do i want gears for an 8.8? Would it be easier to just buy a used rearend from someone who already has 3.73s?
Thanks Alot
Ben

saniutza · Mar 10, 2004

today i'm takin my car to the shop to put the new 355's in... btw i'm a stick guy... and with the pinion and gear i got a RING & PINION INSTALL KIT... the gears were about $140 the kit $100 then labor about $150-200 so you're looking at about $400... my opinion get new parts and not used rear end...

ohh yeah... my mechanic told me to turn the wheel and look at the driveshaft... if the wheel makes 3 turns and about 1/2 while the driveshaft makes one turn then you have 355... so if the tire will turn 3 times while the drivehsaft makes 1 turn then you have 308 ...

donsbad68 · Mar 10, 2004

you have 2.73's

Dustin

Luvmy88 · Mar 10, 2004

Sholdn't you be able to just pull the speedo cable and look at what color gear? Red for 3.73? (too simple?)

hllon4whls · Mar 10, 2004

dvs bullet said:
unless you want to take off the diff cover then you have to count the wheel rotations and drive shaft rotations. It's not extremely accurate but it will give you a good idea if the gears aren't stock. As for the rpm question, sorry I'm a stick man.

The rotating the tire/counting driveshaft rotations can be very accurate if done correctly. You dont do it one time. You rotate everything 10 times to increase the accuracy. If you rotate the tires 10 times, with 3.73 gears, you get 37.3 driveshaft rotations. With 2.73 gears, you get 27.3 DS rotations. With 3.55 you get 35.5 DS rotations. With 4.10 gears you get 41.0 DS rotations.Takes a few minutes and a keen eye, but you can absolutely tell what your gears are with only a jack and a piece of soap (to mark the tire and DS).

91LX-5.0 · Mar 10, 2004

Thanks Alot

Thanks alot guys
You all have been most helpful! I am very impressed with this forum, you guys answer insanely fast, and are very nice with such an ass of a question! I will soon be upgrading to 3.73s for sure!!

Ben

GMstomper · Mar 10, 2004

donsbad68 said:
you have 2.73's

Dustin

He absolutely does NOT have 2.73's...they do 65 at about 1500 RPM's

91LX-5.0 · Mar 10, 2004

Ah Ha,Thanks Stomper I knew I didn't have 2.73s cause the RPMs are way to high, do you think their is 3.08s? or something else?
Ben

GMstomper · Mar 10, 2004

I would say most likely its 3.55's....but with how off the stock tack and speedo can be it may be 3.73's...I would go with LUVMY88 and check the color of the speedo cable gear and count the teeth. I'm dont know which color/# of teeth goes with which rear gears off the top of my head, but its easy enough to find out. No need to take the rear diff cover off. The simplest solution is usually the best....you people are makin this way more complicated than it has to be.

GMstomper · Mar 10, 2004

OK...if you have 3.55's it will have 20 teeth and you will have 21 teeth on it if you have 3.73's. I'm not sure of the colors. Someone else might be able to track them down.

91LX-5.0 · Mar 10, 2004

Thanks a bunch man!
I really appreciate it! After I get the car back (getting new tires and stuff) I will be sure to check!
Ben

saniutza · Mar 10, 2004

91LX-5.0 said:
Thanks alot guys
You all have been most helpful! I am very impressed with this forum, you guys answer insanely fast, and are very nice with such an ass of a question! I will soon be upgrading to 3.73s for sure!!

Ben

Do I have 3.73s?

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