hi guys, is anyone running this combo here? if so....i'm worried about my gas mileage giong wayyy down if i throw 4.11's out back....what rpm's will i be running say at 55mph and at 65mph and 70mph??? should i just go with 3.73's if i'm worried about this or is it really not that bad with the OD? thanks!


jeff

my 3.73s only pull about 2600 rpms at 70 mph
4.11s probably wouldnt be that much higher

You will gain 10.2 percent in rpm with 4.11's over 3.73's on the freeway, with the torque converter in lockup mode.

ok, thanks a lot! still undecided, but i'll figure it out as soon as the time comes for the install.

I would definitely go with the 3.73's for the street. I went with 3.73's and I now wish I still had the 3.42's ....80-85 comes in a 2950, a little high for the high-way.

My fried had 4.11's in his 4th gen Z, untill he drove the car one day when it was wet......He was on the freeway and he went to speed up, and the rear end just got out from under him. The rear of the car started sliding and it knocked up the drivers side fender pretty good when it hit the dividing wall (no shoulder on the road). He went down to 3.73 after that

Gear selection should be considered by cam selection. I was running a 373 in mine[posi was worn out], put in a 342 rear while rebuilding original. I didn't like the way mine ran in third gear at 30 mph. 342s were much worse. I now have 411s and love them. I don't do much state running, but the 411s only run the rpms up about 200 or 250 more than the 373s. The larger the cam the deeper gears you'll need to get smooth drivability.

well the cam i'm using will be the LT4 hotcam with 1.6 rockers so that will be a lift of .525....any suggestions?

I dunno about you guys but 3.42 or 3.45 for the 9 bolts... are a very good match for TPI.....with an auto...i was turning something like 2500 @ 70-75 and with a 5spd it drops to somewhere around 1600..... I have not drvien the car in a while so they are accurate recalls...sorta...lol....