Putting In a 700r4 into the 77 coupe

I bought a conversion kit from monster transmissions that is supposed to have everything minus the crossmember and drive shaft. Apparently, I can use my column shifter but loose the ability to manually place it in low. D is overdrive and the lowest I will be able to manually shift into will be second.

My rear end has a gear ratio of 2.41. What do you guys think i should run?

Also, I may want to run an x pipe instead of the Y exhaust it now has. I guess a good exhaust shop should be able to cut and weld my crossmember. Or should I do it myself? Not the best welder but it don't have to be pretty!

Going to keep the quadrajet and the motor is going to the machine shop soon for a tear down. I was thinking of putting in a mild cam. Any suggestions? I want to keep it tame to get those mpg's!

Lastly, how much should I expect to pay for having my drive shaft cut three inches? Or should I look for a junkyard with a mid 80's caprice and install it?

hugh.stone.rocket wrote:I bought a conversion kit from monster transmissions that is supposed to have everything minus the crossmember and drive shaft. Apparently, I can use my column shifter but loose the ability to manually place it in low. D is overdrive and the lowest I will be able to manually shift into will be second.

My rear end has a gear ratio of 2.41. What do you guys think i should run?

Also, I may want to run an x pipe instead of the Y exhaust it now has. I guess a good exhaust shop should be able to cut and weld my crossmember. Or should I do it myself? Not the best welder but it don't have to be pretty!

Going to keep the quadrajet and the motor is going to the machine shop soon for a tear down. I was thinking of putting in a mild cam. Any suggestions? I want to keep it tame to get those mpg's!

Lastly, how much should I expect to pay for having my drive shaft cut three inches? Or should I look for a junkyard with a mid 80's caprice and install it?

U may find some columns on eBay raw painted chrome up to 33" I've seen just about 1/2" short on out columns but s lil welding and bam it fits
The gears are too low u should look for a 9c1 axle with posi or a 90's impala ss rear end
If you grab the 9c1 axle check of it came with a 700-r4 and if so get the drive shaft
Crossmember is different I think th400 xmembers are close also yoke is different from what u have on the trans end of the drive shaft
Comp cams has some high energy that claim mpg gains along with power
.390/.421/.454 lift

Thanks,

I will check out comp cams.

Definitely need a 3.08 with any of them 4 speeds, my 84 caprice that i had came with a 2.73 with a 700r4, which was ok, but you can definitely get away with (and be much happier in the fun department) with a lower gear. A perfect street combo would be 3.55 gears with a 2000rpm stall with the 700r4, youll be able to smoke the tires or tire for a mile lol but anyway, for the motor, if you do decide to change the cam a good cam for the street on a near stock low compression small block would be a dual pattern, with around a .400 lift on the intake and a .420 on the exhaust, a 112-114 LSA and somewhere around a 200 degree duration @.050 with a bit more on the exhaust side, but that will be a given with a dual pattern cam. If your sending the block to the machine shop have them deck the block to 0, so that way with a .040" standard fel pro 7733pt gasket, your quench will be perfect. I know its more expensive and may not be an option to you, but if you can, just change the pistons to flat tops, and bore it a standard .30 over. That way you will bump the compression up, and it will be a really happy street motor.

I know 700r4s are more plentiful and a tad bit cheaper, but why choose this one over the 2004r? The 700's dont have a very great gear ratio and 1st to 2nd shifts are always hard due to the 1st to 2nd gear ratio. Ive driven many cars with the 700 and every one of them had the same characteristics. And thats totally up to you im not bashing these transmissions or your decision. Just thought id throw that out.

Why the 700r? I don't know. It was time to make a decision. I had been researching and flip flopping from th350 200r4 and 700's for a while. I saw what I thought was a good package deal for the 700 which included the torque converter, wiring, dip stick etc....

Watch now that I have committed to this tranny I will get a call from the guy that has a 77 two door in town that I have been pestering him to sell me. It has all the interior pieces that I need plus a fresh trans and motor build...

I ordered the 2000 stall converter btw.

Ohhhh gotcha, i was just curious and i guess i should have read your post better lol, anyway that 2000 rpm stall will be perfect!

Definitely go with a yard I have two driveshafts for my car both pulled from local yards. They are a perfect fit

and cost next to nothing.(In my case literally nothing but I have friends in yards expect maybe 20-50).

I plan to use a Hurst Quarterstick(older style) with my 200r4 and hence won''t have 1st gear either but really

when do you need 1st gear unless it's a truck?

Thanks for your input. Just so you guys know, I also ordered a basic crate motor from summit today too! I may not have much to report for a few days because I'm waiting on parts, but in the meanwhile:


According to calculations I have done online, my new driveshaft should be 2 and ¾ inches shorter than what I have now. Everywhere else I have read says it needs to be 3" shorter.

Also, I'm double checking that I want to yank a rear end off a donor that has around 3.5 gear ratio correct? I know I asked before I just don't want to buy the wrong diff. I don't want the rpm's to be too high at highway speeds. (350 crate rated for 195 HP, 700r4, and x.xx gears).

One more thing while I have y'alls attention, the rear wheel bolt pattern is gonna be different from the front if I get the rear end off of a mid 90's caprice/roadmaster. Should I get an adapter for the front wheels, or can I get a set of front brakes and hubs that will bolt on so I can rotate my tires in the future.

I'm excited to get her back on the road so thanks for answering my questions.

I wouldn't worry too much below 3.73s as far the rearend ratio goes especially with 4 speed. I don't like 4.56s

though I drove in Trans-Am that had 4.56s with th400 no 1st gear at all maybe you'd hit 9mph lol ok maybe 11.

As for the shaft if you know what you need you will find one in a yard to match there so many lengths that GM

made there is one for you there.

For rear ends, here's what to look for under the 91-96s:

Axle Ratio RPO Code.                   Application
2.56          GM8                   Std. Roadmaster LT1
2.73          GU2                     Std. Caprice L99 (exc. 9C1)
2.93          GW9/GU3            Std. Caprice LT1 (exc. 9C1), Opt. Roadmaster LT1
3.08          GU4                    Std. Caprice 9C1/LT1 (Police), Std. Impala SS
3.23          GU5                     Opt. Caprice L99, Std. Caprice 9C1/L99 (Police)
3.42          GU6                     Std. 91-93 Caprice 9C1/L05, Std. 94+ Fleetwood w/V4P
3.73          GT4                     Std. 91-92 Fleetwood Brougham w/V4P

*V4P = 7,000 lb. trailer towing package... look for a hitch.

Check the RPO/SPID codes to see whats under the car.


Upgrade to the 12" front brakes to get the 5x5 bolt pattern.  There's info somewhere on here about the swap.

How was the final outcome of your 700r4 swap??
I am getting the same crate motor from summit and was looking into swapping my tired THM200 for a 4 speed, not sure weither too do the 700r4 or 2004r...

I am swapping my th350 fora th700 and have some doubt as to which converter lockup kit I should get.
I see they range from under 100$ to about 200$, depending on how many parts are included. I see some of the cheaper kits don't contain the TCC solenoid, which I hear is a good thing to replace, while I am at it.
What do you think?