3.1 tranny on a 3.8?

**vinny of destruction** · 02-25-2011

I have a quick question. Sorry if this is a repost, I searched but didnt find any thing.

what is the difference between the 4t65e on a 3.1 vs 3.8 for 98-02 grand prix?? (the motor is 3.8)
From what Ive read elsewhere its a direct bolt up but I wanna be sure before buying one.

**Poil336** · 02-25-2011

i'm pretty sure they're the same

**GrandZero** · 02-25-2011

I would check the flywheel befor i bought it I think they are different

**vinny of destruction** · 02-25-2011

thats the problem Im looking at buying on line.
and its an automatic btw

**nascartech** · 02-25-2011

3400 and 3800 interchange forsure not sure on the 3100

**vinny of destruction** · 02-26-2011

thanks for the help guys can anyone confirm this ??

**Poil336** · 02-27-2011

you might wanna pm a mod. i expected them to find this by now, but apparently not

**vinny of destruction** · 02-27-2011

will do thanks

**Bio248** · 02-27-2011

4t65e = 4t65e = 4t65e... etc.

the trans in the 3100 car is the same that is in the 3800 car.

**GrandZero** · 02-27-2011

flywheels are different, maybe you can modify one from a f-body

**vinny of destruction** · 02-28-2011

Originally Posted by GrandZero

flywheels are different, maybe you can modify one from a f-body

you mean the flex plate ?? this is for an automatic

Originally Posted by Bio248

4t65e = 4t65e = 4t65e... etc.

the trans in the 3100 car is the same that is in the 3800 car.

Thanks BIO

**BillBoost37** · 03-01-2011

Is the gear ratio the same guys?

**gtpinsc** · 03-02-2011

id call a junkyard that can cross reference it before wasting money on something that doesnt work. i would have thought 3.1's had a 4t60e's. theres alot of factors that could make it not work at least without some work. we dont even know what the op's car is...such as SE,GT or GTP.

**BillBoost37** · 03-02-2011

GP2002.. How do you know it's the same gear ratio? You listed out what looks like an HD trans with 33/37 tooth counts on drive/driven gears and didn't mention the FDR ratio. NonHD transmissions have a 35/35 tooth count on the drive/driven and differing FDR ratios based on the vehicle. In NA Bonnies 4T65E you can get 2.84 or 3.06 FDR's, All SC'd HD 4T65E's had a 3.29 FDR (when combined with the 33/37 it becomes 2.93)

In GP GT's there was a 3.29 diff in the non-hd trans.... I totally forget whats in the W body non-hd normally.

**gtpinsc** · 03-02-2011

i was half right... alot of GM 3.1's had 4t60e's but apparently the GP's 3.1 had the 4t65e.

GM 4T60-E transmission - Wikipedia, the free encyclopedia

**gtpinsc** · 03-03-2011

Originally Posted by GP2002

gtpinsc,

All '97-'03 Grand Prix had the 4t65e trans, no matter if it was a 3.1L or 3.8L.

not "ALL"... my 97 GT had a 4t60e in it.

**BillBoost37** · 03-03-2011

In 97 All SC 3800 drivetains got the 4T65E HD. All 3800 NA's still had the 60 for another year. In 98 All 3800 drivetrains were swapped to the 4T65E whether na or sc.

**gtpinsc** · 03-03-2011

yes it was factory... it was the only year IIRC that the trans was used in a GP and it was only on non supercharged apps.. its the POS vac modulated tranny. but even on some of the latter year 4t65e's the trans cooler lines differed from others.