M6 to Th350 or Th200r4 swap

[1BADAIR]

drive around in 4th on the freeway. 4th is 1:1 in a t56 and 3rd is 1:1 in a 350 so that would be around the same rpm

[mtuggle86]

drive around in 4th on the freeway. 4th is 1:1 in a t56 and 3rd is 1:1 in a 350 so that would be around the same rpm

Good point

[Gottork]

2004r FTMFW

[steddy]

from what I have read, even the TH350 is substantially stronger than a 4L60e.

another thing to consider (and another reason I like the TH350/400) is a taller first gear ratio. The short gear in the 4L60e seems to be designed for lower power vehicles to help generate some off-the-line torque...whereas a high-power car is going to blast right though that. A taller first gear will be more useful and also means you get a shorter jump to second. And I think the taller first gear is the reason many cars will do a couple tenths better in the quarter mile after swapping from a 4L60e.

I've run the same TH350 in the '79 ever since the day I brought her home. Have never had a problem with it. Its been run pretty hard and there hasn't been any hiccups, etc. It's held the power, hasn't minded smokey burns and shifted when I needed it to on the quarter (also holding consistent 12s with street tires and a stock, tied body). It used to skip shift, but that was cleared up by putting a B&M ratchet shifter in (ie, my fault with the stock shifter). A rule of thumb from back in the day is that when you went to a 454 or bigger, then a 400 was used, mostly for the beefier housing (I believe the shift points are a bit different also, though I don't know by how much). The down side is that you won't have OD with either. The TH 350/400 is a straight 3 speed, though I never needed more than that on the quarter and she went out on cruise nights maybe once a week. Needless to say it wasn't a daily driver.

The TH200, I believe was also called the metric 200. I can't say whether or not it was any good, being that I never ran one. The folks I hung around with back in the day were either TH350 or TH400 fans.

The 4L60E in my '96 has a sunshell called "The Beast", which, I believe is either fully welded or fully machined as one unit. Can't think of it off the top of my head. This puts alot more strength into the trans, as opposed to the OEM sunshell being just spot welded, which, if I remember, caused OD to be lost (I may be wrong on this). Total, I think it was like $200. I'd have to look into the receipt book at home. I originally wasn't going to go for the sunshell, being that my build, though extensive, was mild, but the trans was completely rebuilt also, so it did nothing but help things, while it was opened up anyway. I'd say go with the 4L60E if you're going to daily drive quite a bit, for the OD. It'll save some gas.

[steddy]

My '79 has the TH350 with 3.73 gears and posi and, well, to be truthful, I never built the car for the mileage (roughly 8-10 mpg) and I can also tell you that with the TH350, it revs pretty high on the freeway (round about 2500 at 60), but, on take off, it's got a REAL nice pull to it.

[Gottork]

The TH200, I believe was also called the metric 200. I can't say whether or not it was any good, being that I never ran one. The folks I hung around with back in the day were either TH350 or TH400 fans.

the th200 is NOT the 2004r the 200 metric is only behind v6s and no OD, the 200 4r has OD and can be built to withstand MORE than the 700 but thats all I know.. if you wanna know more about the 200 4r look up art carr trannys online or call Mike Ridings, they both love building them.

Chevrolet Automatic Transmission Identification & Description

Automatic transmission types are generally identified by their pan shape.


The THM200 and the THM250 have pans shaped like a THM350, HOWEVER, the THM200 will have the words HYDRAMATIC DIV. and METRIC stamped into the pan. Chevy Automatic Transmission Description & Usage
THM200 - Light duty, "metric" 3 speed transmission.
THM250 - Used in small 4 cylinder cars (Vega, Sunbird, Monza) from 1973 to 1981 and some Nova/Camaro/Chevelle 6 cylinders in 1974 & 75. The 4 cylinder models have 4 large cooling holes near the torque converter, while on the "bigger cars" there are no cooling holes.
THM200-R4 - Used in GM rear wheel drive cars with the 3.8 V6, 305 & 350 Olds and 301 pontiac from 1981 to 1989. This is a 4 speed, overdrive unit.
THM350 - Medium duty 3 speed trans used from 1969 to 1989, Used in Buick, Olds, Pontiac and Chevrolet cars and Chevy & GMC light trucks until 1987. Generally used in straight and V6 and small block engines. Generally able to handle up to 400 foot pounds of torque.
THM375B - This trans is identical to the THM350, but is considered a heavier duty transmission.
THM375 - This transmission is a derivative of the THM400 sharing the external appearance of the 400. It'll be marked 375-THM on the bottom of the tailshaft housing. It's a light duty version of the THM400, has ABSOLUTELY NO RELATION to the THM375B, and was found in 1972 to 1976 full-size cars. The Turbo 375 was modified to accept the Turbo 350 driveshaft yoke.
THM400 - The THM400 was GM's Heavy-duty 3 speed transmission used from 1964 to 1990. Used on large displacement, high torque engines and engines with towing packages. Generally found in Chevy & GM trucks, cadilacs and large displacement engined, full size GM rear wheel drive cars.
THM700-R4 - 4 Speed transmission used in GM cars and light trucks with the 2.8, 3.1, 4.3, V6, Chevrolet built 305, 350 and 454 engines from 1982 to 1992.
4L60 - Early 1990's saw the 700R4 renamed to the 4L60, and "electronic" models were named 4L60E. 4L60 means 4 forward speeds, L = longitudily mounted (rear wheel drive). 60 is the strength rating (less than the 4L80).
3L80 - The 3L80 is a renamed THM400, used in the early 1990's. The 3L80HD would be the THM475 (heavy duty unit).
4L80 - An overdrive model of the THM400. The 4L80E would be the "electronic" model.
Transmissions with a suffix of "C" on the end of the type (THM200C) indicate the transmission has a lock up torque converter.


Transmission 1st Gear 2nd Gear 3rd Gear 4th Gear
GM Power Glide 1.76/1.82 1.00 -------- --------
GM TH350 2.52 1.52 1.00 --------
GM TH400 2.48 1.48 1.00 --------
GM 200-4R 2.74 1.57 1.00 0.67
GM 700-R4 3.06 1.62 1.00 0.70
GM 4L60 3.06 1.62 1.00 0.70


as you can see, the 200-4r has a lower first gear than the rest of OD trannys