Ok fellas I need some input, I'm replacing the stock 350ci. motor in my 78
S.A. with a stroked 412ci(mild cam). This should give plenty of torque and
I'll still be able to pass emissions in Ca. I also want to beef up the
tranmission (3 speed auto THM350) but I don't want to spend much as next
year I want to install a Tremac TKO5, ($3K/kit).
I thought I could get by for a year if I installed a B&M shift kit. Any
thoughts, suggestions, helpful ideas?

A shift kit will do nothing for beefing up the transmission, doesn't matter if it's the B & M, Transgo, or whatever. They just make it shift faster.

Sorry Big Fish, I have to only slightly disagree. Well, add to is more accurate.

As you said, a shift kit won't beef up the transmission. Hard parts are only so strong. If torque is exceeded on a shaft, spline, or case it will break. But the shift kit will make it more resistant to slippage under heavy load. It increases the main line pressure, which applies more pressure to the clutches, which make them grip tighter, which make it more difficult to slip with high horsepower/torque input.

If it does not slip, it will last longer with a stronger motor. The clutches and bands are the weak point in almost any automatic, and the major failure point. So the shift kit does help the trans take more abuse. It is the solution for many racers. It has it's limits. The down side is if the grip allows enough torque transfer, that's when you break hard parts. This does require a really wicked motor, or driver abuse. The second one being much cheaper to come by. That's why we don't let just anyone drive our cars.

I agree with ksyter.. you can be a little more abusive with a shift kit..

he is definitely right about taking it to a new level of failure though.

you can have minor failures without.. but with an SK you always seem to have major ones when they do come.

I personally have not had very good luck with THM 350's, I had a particular 72 caprice 2dr hardtop "sleeper" with a SB 400 that use to eat them like candy.. changed to a thm400 and it never ate another..

ive heard (but never personnaly experienced) that a 700r4 with the right shift kit is one tough mother.

also... ive heard this many many times from transmission guys and in many an old redneck tale that you can tighten up your shift and reduce slippage by adding a small bottle of brake fluid to your transmission fluid. I dont know about the veracity of this.. but i did run this in my thm400... it seemed to help (added to whiplash effect in kickdown ) but it may have just been in my head.

also another trick to make your shifting stiffer is to use type F (ford) fluid. you need to completely drain all of your fluid (especially from torque converter) and use type F. ford used this to make a transmission with fewer moving parts, in doing so they also had a stiffer shift and the fluid is less compressible..

I read this in a corvette restoration guide so the likelyhood of its veracity is pretty good.

I agree with Ken as well, I really didn't think about the slippage factor that is improved with a shift kit. I still don't believe it is a fix for an already tired transmission however.

Agreeded. Worn out is worn out. If the trans is sloppy due to wear, a shift kit will build pressure and it will probably fail faster than with out the kit.

Ford fluid will make a harsher shift, but you don't get the increased pressure on the clutches, just the effect. Line pressure does not go up, the trans is NOT stronger. This is done with the chemical effect and friction quality of the fluid acting on the clutches. Although it does work, I don't think I would want to increase torque transfer to the disc, without increasing the pressure. This may not, but could lead to increased wear on the clutch disc. Worse with more horsepower, not so good either way.

Brake fluid will make the car shift firmer, and sometimes revive a slipping trans. It chemically alters the clutch material and seal material, softening both. The softer material becomes more pliable, thus making worn seals work again. The clutch material softens and swells, making them take up space and grab firmer, and slip less. BUT IT DOES NOT STOP DOING THIS. A little may help, but more is deadly to the trans. The softer material will not withstand as much torque. This may help a wimpy shift, but a lot of horsepower in a hard shift and the soft stuff tears away. AND a little will only help for a period of time. As the seals and clutch material get softer, it starts to come apart. You know what happens next. Rebuild. It's only a matter of time.

Brake fluid used to be very popular for slipping transmissions, so the car could be sold with a working trans. A few weeks or months later, the trans would completely die. Brake fluid does not lubricate, so not only did the clutches and seals fail, the hard parts could be trashed as well. I have seen the results of this several times. BAD IDEA

So what's the answer. Use a good chemical to clean it out, change the fluid, use the correct fluid, fix what's broke, and if you want more, use a shift kit. If you want a lot more, go to a high performance trans. Some high performance trans are nothing be a stock trans with a shift kit. Be sure what you are spending you money on.

How fast do you want to go? How much do you want to spend? The two go together.