Changing gears in my 4T45-E....questions.

[mfuller]

Okay gang, I need some assistance here.....

The vehicle is a 2000 Olds Alero with the 3400 (LA1)
Transmision is a 4T45-E (GM RPO MN5).
Differential/final drive has a 3.05 ratio.
The "side gears" (drive/driven sprokets) under the side cover are 35/35 tooth.

According to my Helm service manual, this transmission was also available with a 3.29 final drive (for the 1999-2005 Grand Am GT only).

If you have the 3.29 FDR, you can have 3 possible chain setups to acheive different effective (overall) ratios:

32/38 ---> 3.91
33/37 ---> 3.69
35/35 ---> 3.29

If you have the 3.05 FDR (like I do), there are also 3 possible chain setups to acheive different effective (overall) ratios:

32/38 ---> 3.63
33/37 ---> 3.42
35/35 ---> 3.05

So, by now you see that my 3.05 overall ratio is not the ideal performance choice for my 3400 V6. But I think 3.63 gears would be too much........3.42 seems like a happy medium.
So drive/driven sprockets, new chain (not a dual chain setup) and a new input speed sensor (I have part numbers for all), plus my DHP PowrTuner........whaddya think? Any other parts I'm missing (aside from gaskets, etc.)?

TIA

[geldartb]

i was talking with another memeber probably the same one you got the list from and from the parts you named thats all you need.

well beside the dhp to fix it.

im aimin for the 3.69 since i got the 3.29 FDR

[sprucegagt]

Why do you need a new ISS?

[mfuller]

Mostly because I compared various part numbers for the RPO MN4 and MN5 transmissions, and the part number for the MN4 with a 3.42 overall ratio is different.

[95Grand-Am]

Wouldn't it be a lot easier to put the 3.29 diff in your trans? You wouln't have to change the drive and driven sprockets which would save alot of time, if you were only going to change to a 3.42. There isn't alot of differance between 3.29 and 3.42 only which would be barely noticable.

[sprucegagt]

To pull the diff in a 4T45E you have to remove everything including the drive sprockets and clutch pak. There is no cover like the 4T65 cases have.

Mostly because I compared various part numbers for the RPO MN4 and MN5 transmissions, and the part number for the MN4 with a 3.42 overall ratio is different.

Part number? I take it the connectors are the same between the MN4 and MN5 units? Strange that GM would use different sensors just from a sprocket ratio change.

[mfuller]

Part numbers:

Link Chain - #24200738
Input Speed Sensor - #24218077
33 tooth drive sprocket - #24204710
37 tooth driven sprocket - #24204713

I've long since given up trying to decipher GM's reasoning.
I think 3.69 gears might be too much unless you plan to rev to 7 grand and make all your power above roughly 5 grand. 3.29s don't provide any great benefit over 3.05s in my experience.......like I said, I think 3.42 is a good compromise between performance and driveability.

[sprucegagt]

Thanks and I agree.

3.42 shouldn't hurt cruising MPG to bad. I would expect it to be around 2500 - 2800 rpm at 75 mph. But it would certainly help 60 ft times, if you can get traction.

EDIT: Are the drive sprockets and chain sold as a matched set?

[geldartb]

24228912 Chain Drive/ W Sprockets Ratio 1.1875:1 Ratio w/ 3.29 = 3.91 which he doesnt have a 3.29 so its obviously lower

comes with the sprockets and chain its way cheaper than adding up all the numbers he listed

for me it would be 176.67 shipped from gm parts direct for the part i posted plus the speed sensor

if you buy them seperately like you listed its like a 100 bucks more

[gectek]

ok so first off u do need a new sensor for the changing in gear sprocket driven and drive ratios because it produces a different pulse and you will need the diff sensor provide the right pulse. also u have to change the ratio with the PT...second the 3.91 does come as a set, but good luck tryin to find the chain and sprockets in the 33/37 ratio, its very hard to find them. also the 3.91 that i am running has not affected my MPG at all, because it helps keep my engine in its powerband alot better, and with lockup, im only pulling 2300 rpm at 70. plus a small change in gear ratio is a big overall change due to the driven ratio of the different gears...only in 3rd gear is the regular 4t45 3.29, 1st and 2nd are tq multipliers, and the 4th is overdrive, plus add in lockup, which will take down 2-400 rpm. even a 3.29 from a 3.05 is a big jump. i have trouble burning out everywhere even when im going 20 and floor it due to my gear ratio, i need some very grippy tires now to keep traction.

and the only reason i charge more for it than GMparts direct is because i have to pay tax, and i include the labor it takes to rebuild the trans...so i dont have a huge bill at the end plus the labor...

[mfuller]

What settings did you change in the PowrTuner to make the new ratio OK? I was under the impression that there are other tables that need to be modified - tables that we don't yet have access to.

[sprucegagt]

I would say the following tables would need to be modified:

Drive_Sproket_Ratio
Calculated_Pulses_Per_Revolution (Which I think would be 29.46 (33/1.12) for a 33/37 gear set)
Pulses_Per_Mile
Max_Shift_RPM
Shift_Point_Cruise Tables
Shift_Point_Hot Tables
Shift_Point_Normal Tables
TCC_Apply_Normal_Line Tables
TCC_Release_Normal_Line Tables
TCC_Apply_Hot Tables
TCC_Release_Hot Tables
and
All of the Torque Reduction tables

Would anyone care to add to the list?

[gectek]

the tcc apply tables work just fine no need to change them at all. of course the top speed, the max shift rpm, the cruise tables are just fine as well. as long as you dont mind shifting at about 6500 there really is no problem, i shift at about 6800 and its alot of fun. yah also take the calculated pulses per revolution to 32, then just worry about the torque reduction, and shift normal and shift hot modes, and change the high rpm fuel cutoff tables, and torque abuse rpm enable, those will make it run in very good fashion

[sprucegagt]

List updated

[gectek]

y ru dividing by 1.12, it calculates the pulses as they are read right off the drive sproket which would be 32/33/35