Gear ratios / RPM @65Mph

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Dec 16, 2008 | 01:20 PM

#21

Ratracer

Senior Member

Joined: 08-18-2008

Posts: 508

From: Moved to Camaro 5 forum

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.

Dec 16, 2008 | 01:34 PM

#22

ChevyMgr

Founding Member

Joined: 11-23-2007

Posts: 8,210

From: Texas

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.

Dec 16, 2008 | 08:40 PM

#23

c2vette

Senior Member

Joined: 11-27-2007

Posts: 1,115

From: Austin, Texas

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.

Dec 17, 2008 | 11:55 AM

#24

LT1GMC

Senior Member

Joined: 01-28-2008

Posts: 357

From: INDIANA

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.