I was wondering if anyone has done a manual transmission swap on a 2005 Monte Carlo LT 3800 because I’ve been wanting to attempt it but need some advice on what transmissions people think would work even with some modifications needed

 

As the monte never came with a manual transmission, they all require custom work to install.

Transmissions that have been done on a 3800 / physically bolt to the engine (as long as you get the model with the right bolt pattern):
-Getrag 282, 5 speed from the 80s/90s
-Getrag 284, 5 speed from the early 90s but very low production numbers (3.4 dohc cars). Could be very tough to find one in good shape these days.
-F23, 5 speed from the 2000s
-F40, 6 speed from the 2000s

Certainly if you wanted to get into adapter plates, practically any FWD transmission could be adapted but you'd be blazing a new trail.

The one thing to keep in mind is torque rating, especially if you're modded. Some of these were designed around either very old v6s or I4s (often in cars with much lower gross weight) and have factory torque ratings below that of even a stock NA 3800. Every one has been put behind much higher torque engines (I want to say there was one 284 pushed north of 600 wheel), especially in light Fieros, but plenty of them have also been broken as well. Id just take power comparisons with a grain of salt as someone daily driving a Fiero on street tires is going to be a lot easier on hard parts than a full weight W on slicks /DRs doing drag duty at the same power level.

IMO the best resource for reading up on them are the Fiero groups. They seem to do a ton more manual swaps than W bodies and newer model 3800s get swapped into them often as well.


One thing to keep in mind with the F40 - 6 gears may sound cooler, but 1st gear is useless if youve got decent power. A 4t65HD has a 2.92 1st with a 2.93 FDR (and folks struggle to hook 1st with street tires). But the F40 is is very high 3s to low 4s for 1st with a FDR in the mid to upper 3s (there were lots of variants with different combos).

Steep gearing is a common theme across them in general though due to the low hp engines they came behind. So you may find under WOT use that you may end up skipping the first gear or two, even with a 5 speed models.

 

I know two guys personally with 5-speed manual swapped Grand Prixs. The one is using a trans found in an early 90's Lumina and the other guy is using one from a late model Cavalier. I should know the models but I don't. They both had some work to make it happen. Modifying the subframe, pedal clusters, wiring, PCM programming.
I believe there is a Facebook group dedicated to people doing 5-speed swaps on w-body cars like the Monte. I have seen someone who did it with an Impala. So even though I never saw someone do it with a Monte, given Grand Prix guys and an Impala guy did it, it can me done.

 

There is a post from a few years back where one of the members on here did a manual swap but I think he did it with a 5th gen MC. If I recall corectly he got something from a Pontiac.