Stock 02 Z71 Tahoe Gearing
11-03-2006, 04:09 PM
#1
Stock 02 Z71 Tahoe Gearing
As mentioned, I have a 2002 Z71 Tahoe, just put a set of BFGoodrich TA KO 285/70/17's on it, and had a quick question. I could have swore I read somewhere that these things had 3.73 gears... My gearing seems much taller than that. At 70 or so I'm barely taching just abve 2 grand. Let me know if they're 3.08's or 3.73's, or whatever the heck they are!
Tony
Tony
11-03-2006, 04:23 PM
#2
Hopefully this comes out right.....
70 mph = 73920 inches / min
Tire diameter = 32.7 inches
Tire circumference = 102.73 inches
Tire RPM = axle RPM = 719.56
Engine RPM = 2100 RPM (assumed from your statement)
4th gear ratio 4L60E = 0.7
Trans output shaft RPM = 2100 / 0.7 = 3000
3000/719.56 = 4.16 gear ratio
Did you change tire sizes? If so - did you recalibrate your speedo? If all that is taken care of, seems like you have 4.10 gears.
If you had 3.73's it looks like you would be running at about 1900 RPM at 70mph.
70 mph = 73920 inches / min
Tire diameter = 32.7 inches
Tire circumference = 102.73 inches
Tire RPM = axle RPM = 719.56
Engine RPM = 2100 RPM (assumed from your statement)
4th gear ratio 4L60E = 0.7
Trans output shaft RPM = 2100 / 0.7 = 3000
3000/719.56 = 4.16 gear ratio
Did you change tire sizes? If so - did you recalibrate your speedo? If all that is taken care of, seems like you have 4.10 gears.
If you had 3.73's it looks like you would be running at about 1900 RPM at 70mph.
Last edited by thunder550; 11-03-2006 at 04:32 PM.
11-03-2006, 04:32 PM
#3
Here ya go, you can check my math here
http://www.csgnetwork.com/multirpmcalc.html
3.08 rear end = 1551 RPM @ 70 mph
3.73 rear end = 1878 RPM @ 70 mph
4.10 rear end = 2064 RPM @ 70 mph
http://www.csgnetwork.com/multirpmcalc.html
3.08 rear end = 1551 RPM @ 70 mph
3.73 rear end = 1878 RPM @ 70 mph
4.10 rear end = 2064 RPM @ 70 mph
11-03-2006, 04:50 PM
#4
Yes, I had 265/70/17's on it, went to 285/70/17's instead. The speedo will be off like 2.5 mph @ 70 mph so when it says 70mph I'm really going 72.5. I will verify the rpm/speed and report back. BTW - No easy way other than tuning software to recal for tire size changes right?
11-03-2006, 05:09 PM
#6
That'd be even better... I'm kind of a n00b when it comes to the 5.3 in the trucks/suv's. The intake is completely different, as well as the induction system. Is there a system like on my TA where I can replace the box with a "lid" and make a world of difference like the F-bodies? What about TB bypass, free mods? LOL Not even really sure where to start. Definitely could use a new set of tr55's and wires. I'll research the RPO and see if I can't find out what it's got!
11-03-2006, 05:18 PM
#7
Look inside your glove box, I think that's where the codes are listed. I just don't know what they mean. I'm sure if you search you can find them though.
There's no lid mod unfortunately, and the TB bypass can be done easily (pull coolant tube off TB and re-route to the crossover tube on the heads. It's long enough to reach.)
Some guys have used a hole saw to cut some holes in the stock airbox as a free mod. Don't bother with aftermarket wires unless you like the color, general consensus is that the stock wires are just as good as any aftermarket ones. There was a website floating around here for awhile with the free mods listed, but I can't remember what it was.
There's no lid mod unfortunately, and the TB bypass can be done easily (pull coolant tube off TB and re-route to the crossover tube on the heads. It's long enough to reach.)
Some guys have used a hole saw to cut some holes in the stock airbox as a free mod. Don't bother with aftermarket wires unless you like the color, general consensus is that the stock wires are just as good as any aftermarket ones. There was a website floating around here for awhile with the free mods listed, but I can't remember what it was.
