According to my window sticker and glove box sticker I have 3.42's. But unless there gearing tranny's different I think I have 3.73's or 4.10's. My buddy has a tahoe with 3.73's and he turns 1900-2000rpms at 70mph. My Yukon turns 2100rpms at 70mph. At 75 its about 2300rpms. Can this be right?

If I do have lower gears I'm going to be pissed!!!!!!!!!!!

 

My Silvy with 4.10's and shorter tires runs 2500rpms at 75mph, so I know its close.

 

Are the tire diameters on both vehicles identical? If not, you aren't comparing apples to, well, apples.

 

Read the RPO codes in the glove box. Should be one of these!


2006 RPO - GMC Yukon/XL

G80 Differential, locking, heavy-duty, rear

GT4 Rear axle, 3.73 ratio

GT5 Rear axle, 4.10 ratio

GU5 Rear axle, 3.23 ratio

GU6 Rear axle, 3.42 ratio

It more than likly the tire size differance giving a differant rpm indication between the two.

 

I have 265/70/16's with GU6(3.42). He has 245/70/16's with GT4(3.73). My tires are taller and my gears are higher. I should read much lower rpms than him at 70mph, not 200rpms higher. Thats just not right. I need to look and see what gears they come with. It has the heavy duty tow package, but you can get that with 3.42's right?

 

i think it may be 4.10s.. i have 255/75/16's and 4.10's and i run roughly 2300 rpms at 75mph.. lol uh oh...

 

Is that on the lower side of 2300 or the higher side of 2300? The only available gears for my model is 3.42 and 4.10. I may have to find out for sure, but how?

 

i believe my truck was at a little over 2000 with 3.73s and 255/35/20

 

I have just to the opposite problem. My truck has the towing package and I thought it had 3.73 gears. But it actually has the 3.42s. So, I m pissed over that now.

Hey, think we can convince GM they screwed up our trucks and they need to swap the gears out under warranty? I think they got my order and yours mixed up and now they need to fix it.

 

Pm me your vin# and i'll run it and check the vehicle build through gm to see if it matches your rpo sticker. Also, I wonder if you do have the correct gear, is your
converter locking up in 4th? Have you compared the 2 trucks in another gear other than 4th?