supposedly i have a TH200 tranny in my 305 4bbl 1982 Z-28, and i am now out of debt on the car, so the mods start here. Im looking for some mods to make my car scary fast. Future plans are to do a 355 motor. First i want to attack the tranny and the rear end, so when i do get the motor in the car, nothing grenades. I was thinking of a 3.73 posi rearend from a late 80's iroc. Ist this a good strong rear end, or does anyone have any other suggestions. Also i heard the tranny was a piece, so i was thinking of installing a 700-R4 tranny also out of a late 80's iroc. This tranny would have a stage 3 shift kit, and a 3000 stall converter. If i want to replace my existing tranny in my car right now, would i need to switch my crossmember for a 700-R4, and would i need to mod anything else for this swap?? Any information is greatly appreciated, as i have this buddy who is willing to sell me his tranny, out of his iroc. Thnx again,

Nick

Hey pimp, replace thjat 200c with a th350. All you need is a bracket. B&M makes one

if you can get all the supporting parts for the 700r4 swap- crossmember, torque arm, driveshaft, shifter- i'd go that route. it would be a direct bolt in.

what is stronger, the TH350 or the 700-R4. The TH350 swap sounds pretty good, how many speeds does it have???

The 350 is a 3 spd old school auto. The 700R4 is a 4 speed overdrive with a lock-up converter. It would take more work and money to go the 700R4 route, but it would reward you with better performance and better fuel economy.

thnx, so if i want to go with the 350, then is the car going to top out at a higher speed than with the Th200c? because right now, the guages reads a max of 85 mph. Will the th350 make my car a little faster?? Also, how much power can the 350 handle around??
Thnx guys

The 350 is the cheapest way out. Used ones are everywhere, and rebuilts are cheap. The only new parts you will need are a torque converter and the arm bracket. No new Driveshaft, etc. They are stronger than a 200c, and can be built tough. A $30 B&M shift kit is easy upgrade too. Watch the speedo gears (as in any swap) so the speedo still reads right. The OD swap requires more parts, that maybe you can get from a donor car.

But it is a 3 speed auto, final drive is 1:1, just like the 200c so the th350 won’t increase top end. BTW, just because the gauge only reads 85 doesn’t mean you can’t go faster than that. An overdrive trans, like a 700r4 or a 200r4 will by offering a lower final drive gear.

If $$ matters, a 350 is the way to go. But I would want an overdrive.

Chek out http://thirdgen.org/techbb2/

so, if i plan on having around 400 horses to the pavement later on, can the 350 be built up?? Also if i want to take it to the drags with this much power with the 350 tranny, will it have a problem with speed being topped out, before i reach the finish line?

so, if i plan on having around 400 horses to the pavement later on, can the 350 be built up?? Also if i want to take it to the drags with this much power with the 350 tranny, will it have a problem with speed being topped out, before i reach the finish line?

If you need a trans now, then don’t worry about it. But yes, a th350 can be built to deal with that all day long.

In regards to speed, your rear gears & tire height are (a bigger) part of the equation.

i plan on running around 3.73 to 4.11 in the near future.....

Then an OD might be a good idea.

so how hard is it to intall a late 80's 700R4 that came out of an iroc, into the 1982 Z28?

Found this link at www.thirdgen.org, where I've tried to send you before. As said in the past, not trying to keep you out here, but you'd get better answers over there.

http://chevythunder82.tripod.com/TrannySwap.htm


Also from www.thirdgen.org

Q: Can I replace my 700R4 automatic tranny with a later model?

A: Yes. In fact, if your car was built prior to the 1987 model year, it's probably a good idea (if you have the cash). In 1987 (and even on some of the very-late-1986 cars), a number of improvements were made to the 700R4, the most prominent of which was a change to the auxiliary valve body with the main body and stronger components. This valve body is a section added in conjunction with the full valve body that routes the fluid differently. Earlier versions simply have a cover plate in place of this valve body where a small amount of fluid reserve is kept for some operation. The newer model has an accumulator to regulate the engagement of the forward clutch so that the shift into "D" would be smoother. An abuse valve was added which, based on throttle position, would short circuit the accumulator and cause the "D" shift to occur faster (benefits apparent when rocking a car that's stuck in snow or sand as it causes the clutch to engage faster to eliminate slippage and heat built-up). These two items were also made applicable to the engagement of the reverse clutch, thus smoothing its operation except during "abusive" conditions.

The auxiliary valve body is on the drivers side, just behind the trans valve body (opposite the accumulator housing). Four bolts hold the a 6 x 2 inch block in place with a tube a tube connecting it to the front-side of the main valve body. You can tell if you've got the auxiliary valve body without pulling the pan. The later tranny has a slightly deeper pan to accommodate the auxiliary valve body. To make certain identification, GM changed the pattern of markings on the pan bottom where the magnet is located. These markings are visible from the underside, near a rearward corner, forming a square shape of size 1.75 inches or so. The later pans (accommodating the auxiliary valve body) have unequal length lines (one set is longer than the rest) unlike the earlier pans which have all lines equal length. Also, behind the torque converter, look for a casting number on the front pump. If the last three digits are "732", then you have the new, improved version of the 700-R4.

The newer trannies also have a 10-vane pump instead of the old 7-vane pump (more pressure results in quicker, firmer shifts and tranny longevity).

If do want to upgrade, you should check that the input and output shafts will function with your existing converter and driveshaft. One of the other upgrades for 1987 was the change of the input shaft from a 27 spline to a 30 spline. But keep in mind that there have been subsequent changes after 1987 as well. Your best bet is to use the most recent model you can find.

But, also remember that if you want the shift points to remain the same as before, you should try to get one from a similar auto and engine since the valve body springs and the governor are sometimes different for different auto and engine combinations. In some cases the differences are subtle and others not. The valve bodies on the early 700R4s are not interchangable with the later models, so you do not have the option of simply swapping valve bodies to get around this issue. Also, note that if the newer tranny has an electronically controlled shift, it can be overridden.


There are some questions as to the ability of a 700R4 to withstand higher HP, and some feel the 200R4 is a better choice. I do not know how the 200 and 200R4 compare in terms of mounting, but if they mount the same and the 200R4 can withstand more power, then a 200R4 is the way to go.

a 200r4 would be a good idea- except you would be on your own figuring out the torque arm mount. there are ways to make them stronger than a 700r4.
the overall length is the same as a TH200 or th350, but the mount is farther back in a different location than any other GM trans, so the crossmember mounting might need some engineering.
all things considered, i'd go with the 700r4- especially if the one you can get is already built up and you can get all the mounting hardware to put it in.