transmission question on a v6 87 monte carlo

[87luxsprt]

So i have a 87 monte carlo LS v6 with a floor shift 3speed auto transmission. I have no overdrive. So i wanna install a 200r4. With the overdrive. My question is does anybody know how hard will this conversion is. The 200r4 will be off a colum shift 86 Monte Carlo v8. I currently have 24 inch wheels. So i feel like i do need that overdrive. On the freeway. If i let go of the gas pedal instead of kinda coasting it lowers my speed like right away.I feel like am really forcing that 3speed transmission ... Thanks for any ideas.

 

[DRIVEN]

By swapping in the overdrive you'll just be working the engine and transmission that much harder. The reason the car decelerates so much when you let off the gas is because of those big steam roller tires. That's a ton of rolling resistance. If you upgrade to the 200-4R alone it's a step backwards. You will need to re-gear the rearend too if you want the combination to work well. The 200-4R is basically a bolt in swap if you get the crossmember from the donor car. Obviously the shift indicator won't line up but it should still work. The proper thing to do is get the matching floor shifter parts too. For the rearend you'll probably need something in the 3.55-3.73 range to compensate for the overdrive. It'll also make a huge difference in acceleration. Your 4.3 won't be happy with the tall factory gears, overdrive and big wheels. Try plugging your specs in here to help select the right gear ratio.
http://www.angelfire.com/fl/procrastination/rear.html
For example, I found that with my car I needed to replace my stock 2.29 gears with 3.42s to keep the same cruise rpm when I swapped in a 200-4R for the original TH200. It basically made the car way quicker but let me keep the freeway mpg. Remember that GM engineered these combinations for maximum economy. Cruise rpm is important. Changing it very much in either direction is likely to give undesirable results.

 

[87luxsprt]

WOW great information!!! Do u think i should also get the rear end off the donor car.

 

[Evan11]

WOW great information!!! Do u think i should also get the rear end off the donor car.

If its a base model monte that has the 200r4, it will still have tall gears like 2.56 or 2.73 gears, doubtful but it could have 3.08gears. If you can find a 83-87 monte ss rear end, it would have either 3.42 or 3.73 gears, depending on the year. which is what u need for those huge wheels with overdrive.

 

[DRIVEN]

You'll need deeper gears. I played with the calculator that I linked but had to guess at the numbers (because I can't measure your wheels). If you swapped in the 200-4R and 3.73 gears you'll only be turning 1800rpm at 65mph -- using 30" (guessing) as your tire diameter. That's actually about the same cruise rpm you have now (assuming you have 2.41 gears) with the 3speed. You may need even lower gears to get to a better cruise rpm. Those big wheels might actually need 4.11s or even 4.56s. You'll really need to run the numbers yourself to be sure. I would think 2200-2500 is a pretty safe target for cruise rpm. Less is kind of lugging a 4.3 -- and more is probably going to hurt mpg.

 

[TexasT]

If you do decide on the 2004r swap hit your local recycler up and look for a big Cadillac with one. Look for one with the fluid nice and cherry red. I'd get the torque converter, TV cable and the brackets off the carb and maybe the carb too. Also the plug and such for the lockup. Dipstick and tube. Look for one that has the AA code on a yellow tag on the passenger rear of the trans. Be sure to read up on the tv cable and its proper adjustment to avoid a burnt up trans.

 

[87luxsprt]

I really just though i was gonna be able to plug in play with that transmission never knew all this stuff about the gears.

I was checking out this link http://www.c2e.info/rpocodes/gmrpocodesGthroughM.html
it tells you what gears u have if the car has never been tampered with. After looking at my trunk tag i found a GH2 code. Which means am running 2.29 super LOW isn't???

Again thanks for all the information