Gear ratios / RPM @65Mph

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12-16-2008, 01:20 PM

#21

Ratracer

Senior Member

Join Date: 08-18-2008

Location: Moved to Camaro 5 forum

Posts: 508

Quote:

Originally Posted by cannuck

at what mph does the auto shift for each gear at normal acceleration occur

I know that it shifts 3rd to 4th at about 47mph. My rural drive is @ 45mph, but I ease up the speed to get it to shift into 4th, to knock off RPM's for a little fuel conservation.

12-16-2008, 01:34 PM

#22

ChevyMgr

Founding Member

Join Date: 11-23-2007

Location: Texas

Posts: 8,210

Quote:

Originally Posted by cannuck

at what mph does the auto shift for each gear at normal acceleration occur

There really is no normal speed for the shifts. Lot's of data is sent and received by sensors and the transmission control module based on fluid pressures, ambient/trans/engine temperatures, load and others. If the auto transmission isn't shifting correctly your Check Engine Light will come on and set a code.

12-16-2008, 08:40 PM

#23

c2vette

Senior Member

Join Date: 11-27-2007

Location: Austin, Texas

Posts: 1,115

Quote:

Originally Posted by Nebulous1

Are you sure those are the correct numbers? Check out http://media.gm.com/us/powertrain/en...08/08truck.htm. Check out the spec sheets for the LNF's transmissions, both 4T45(MN5) and F35(MU3).

4T45/MN5 shows:
First: 2.96
Second: 1.62
Third: 1.00
Fourth: 0.68
Reverse: 2.14
Final Drive Ratio: 3.05, 3.29

F35/MU3 shows:
Gear ratios: MU3
First: 3.38
Second: 1.76
Third: 1.18
Fourth: 0.89
Fifth: 0.7
Reverse: 3.17
Final Drive Ratio: HHR SS - 4.05

I could not find the relevant thread, but some time back it was indicated that some of the ratios on that site are apparently incorrect.

12-17-2008, 11:55 AM

#24

LT1GMC

Senior Member

Join Date: 01-28-2008

Location: INDIANA

Posts: 355

Quote:

Originally Posted by XXL

Like I did in my post above?

La Machine.

Your post did not show how you got the second number, that you multiplied the final drive by the gear ratio, I explained it so others would understand.