hello, got a 70 skylark with a 455 out of a 73 riv, has a th 350 currently and plan on upgrading the valve train, heads and pistons, probably gonna get ram air eventually. Point being i plan on having a pretty beefed engine, So first thing is is it needs to be tough enough, 2nd my application of the car is mainly for crusing, maybe a lil street draggin, and occasionally actually taking it to the strip. Id like to put 3.73 - 4.10 rear ratio in. I know the muncies are the historically correct transmission to install but with that deep of a rear, when going crusing on then highway id like to not have the rpms wound so tights. Which lead me to maybe doing a 200-4r, due to the ease of the conversion from a 350 to a 200-4r and also the overdrive, but as i think about it, to not make betty run on 2 legs every once in awhile would be a sin, plus nothin beats slammin gears. My options ive looked at for manuals are a muncie pulled or bought, or a new autogear version, richmond super t-10, or the richmond super 5 speed. Idk much about them but ive heard of tremec making some decent options. Originality is not of too much concern, im more interested in performance and cost efficiency. Im partial to the super 5 speed due to the overdrive in 5th. Also info on the amount of work to complete the conversion would be appreciated. Thanks in advance for any info! Respectfully, BigSmo54
I have the 5 speed tremec tko600 behind my 70 Skylark 350. This trans is rated for 600ftlbs. Car drives great. Shouldn't have any problems handlng your 455 and it gives you the option of a .82 or .64 overdrive. You just have to decide what clutch you would like. I strongly recommend a hydraulic clutch set up. The feel is really nice for the street. Plus it gives you added clearance for headers, if you have them. You can also use a factory bellhousing and cross member. The main thing to be aware of is making sure your crank is machined for a pilot bushing. If not, the engine will have to be pulled in order to have this work done. Not expensive, just time consuming. Second, is the trans tunnel hump will have to be modified. There are templates available from companies like SST, but usually it requires you purchasing from them in order to aquire this template. I honestly feel the template is not necessary. You can take measurements yourself, locate the shifter and go from there. There is a great post by another member about converting to a manual from an auto. In this post there are many specific details, parts lists and dimensions. This post was for a 4 speed though. Still, should help a lot. Hope this helps with your decision. Feel free to ask for any more details. Best of luck
My car has a 200-4R behind my 462. Rear gear is a 3.73. On the highway 70 mph is just over 2,000 rpm's. Much better than over 3,000 with the TH400. It just has to be built to handle the power as they were originally put behind engines with about half the power and torque of a 455. I actually have a post that journaled the installation in my car. http://www.v8buick.com/index.php?threads/installing-a-200-4r-in-a-1970-gs-a-tutorial-pictoral.68307/
I would go with the Tremec TKO600. I know Richmond makes 5 speeds that are not overdrive in 5th gear. 5th gear is 1:1 and 1st is super low so you would probably need a 256 rear to get what you want.
I used a Richmond super street and wish I would have went with the TKo 600. Although the trans is physically smaller The external shift linkage makes shifting difficult compared to the Tremec's.
I have a Tremec tko500, and love it, except i had to cut the floor hump. It has a deep 3.27 1st gear, and a tall 0.62 5th gear. The rear is a 3:31 gear ratio. Equating the gear ratios to my old wide ratio Muncie (2.56 1st gear, 1:1 4th gear) using a 3:31 rear gear, the Tremec would be the same as a Muncie with a 4:22 rear gear in 1st and a 2.05 rear gear in 4th.
Since you already have an automatic, the swap to a 200-4R would be a snap compared to the manual change over. I do understand the appeal of a manual though. I have 3.73s and a 200-4R in my 70 462 Stage 1. It has held up well over the years. With the low first and overdrive, 3.73s launch like 4.30s and cruises like 2.73s.
