betooz

I've decided not to throw away anymore $ with the 4L60E.

I'm taking the plunge and going to a 3 spd.

Should I do the TH400 or 350?

Any disadvantage with one or the other?

Please advise.

Any pros and cons to both would be great! Thanks for your time.

comp

need more info on your combo.

aj1988

If you are going to go with a TH then you should go with a 400. It was the heavy duty tranny offered back in the early 70 with the high torque engines. I had one in my 72 that I had rebuilt with a stage II shift kit and there was no doubt when it shifted.

CFI-EFI

Between the two, the gear ratios are virtually the same. With a 2.48 or a 2.52 first gear, you will lose some of the off the snap you get with the 3.06 first gear in the 4L60E. The OD trans CAN be beefed, significantly. My builder rates mine at 700+ hp, and it bolts in. Either TH trans will require driveshaft mods and adaption to the "C" beam. The TH400 is bigger, heavier, and eats more horse power than the TH350. The TH400 is beefier and will require less money to hold up to a given level of power. Like the 4L60E, the TH350 can be built to withstand incredible amounts of power, probably more than the 4L60E. With either TH, you lose first gear reduction AND the overdrive. Not to mention the lock up converter.

RACE ON!!!

gunslinger1971

You lose a little more power through the TH400, although the strength makes up for it in my book.
The TH350 is geared a little lower in first and second gear but not much.
The Th400 weighs more, and its getting harder to find cores at salvage yards.
A properly built TH350 can handle a good amount of power.
TH400 has electronic kickdown and the TH350 has a cable going to the carb linkage.

All that being said, I built a stroker big block for my Chevelle a couple of years ago and the TH350 that was in the car lasted a couple of hours. I found a rebuildable TH400 core at a local salvage yard for $100, had a Fairbanks shiftkit installed and a rebuild and torque converter replaced and had less than $600 in the setup. Havent had a problem with it yet.

I would go with the TH400, but dont rule out the TH350 if you have a rebuilder you can trust.

0ski_dwn_it

why don't you buy my trans/converter off me and let me do the TH350 swap first

I all seriousness I want to do the same thing. My tranny is great and works perfectly, but I think the T350 with the 2.52 gear would work great in this car.

The 350 will take less power from your setup as mentioned, and if built RIGHT, will take more power than 99% of the people here can throw at it.

The 400s are great, but if your going to make the swap, get the extra HPs you can get with the 350, not to mention the adaption for the 350 will be easier.

Now when you taking order for my tranny/converter?

comp

need to know what you want and have

CFI-EFI

I think if he had a builder that was capable and was ASKED to build a stout 4L60E trans, he wouldn't be considering a swap.

RACE ON!!!

vader86

I would try to get the 4L80E or TH400 with a Gear Vendors OD (4L80 is the electronic generation of TH400 we use today in trucks), if youre going to be making gobs of power and want it to withstand the power, but it will suck up more power to run a 400 than it will a 350. 350s can be built stout and rebuilds are going to end up being cheaper.

Gear ratio drops in 1-2 between either of these and the 700 is excellent in comparison, youll lose some off-the-line snap, but the closer ratio in these 2 will give you gains in ET.

The problem with any Automatic is finding the right builder. They can be built with lockup converters.

CFI-EFI

The 4L80E is an overdrive version of the TH400. A Gear Vendors OD used with that trans would be redundent. The 1st, 2nd, and 3rd gear ratios are the same as the TH400. There never was a non-electronic version. Only the electronic, 4L80E.

RACE ON!!!

comp

we still don't know what he want's ....If 400 and less on HP & torque
a warm T-350 up to 450 on both a worked T-350 past that YES i'd
do a Hot T-400

vader86

WTF are you talking about now? I didnt tell him to stick a GV unit on a 4L80E, I told him to put a GV unit on a Th400 so he'd have an overdrive.

aj1988

Patience there Grasshopper. If you go back and read your first post quickly, you can easily get out of it that you said the 4l80 and th400 need an overdrive. If you would just write slower for us slow readers, there wouldn't be a problem.

vader86

No what I see is CFI being his usual smartazz self and trying to tell me things he thinks I dont know.

Perhaps from now on I should italicize or bold every other word, like he does, so that he can finally grasp usage of the English language.

CFI-EFI

I am NOT being a "smartazz". I am NOT guessing at what you may or may not know. I am not even addressing YOU. I am simply trying to clarify WHAT the transmissions ARE for other slow readers like myself. I didn't attack you or your knowledge.

The word OR sure looks like the comments apply to both named transmissions. You DO bother to mention, "4L80 is the electronic generation of TH400 we use today in trucks", but you forgot to mention it is an overdrive trans. And since YOU seem so willing to pick nits, there is not, nor was there ever, a "4L80" transmission.

You NOTICED! It must work. My crystal ball is in the shop. I can only read, what you write. It isn't MY, "usage of the English language" that is in question, here. A little sensitive, are we?

RACE ON!!!

4DRSS

Did you see this thread?

Betooz has a Nu-Tek 396 making about 525 HP @ 6,700 RPM. He has been through 4 4L60E's the last few months built by a reputible builder. The tranny does not like the high revs.

I recommended the TH400 with a reverse manual valvebody, that is what I am using in my 650 HP Impala SS. What is needed to adapt the C beam to a TH400? Who makes a kit? Is a custom length driveshaft needed?

4DRSS

Oh and I would say his first priority is reliability. The car is 99% a street car so I think the taller first gear would actually benefit him, his car is a torque monster and just lights them up on the street.

The engine has been in his car almost a year and he hasn't had a tranny last over four weeks yet. That's using two different builders too.

betooz

Thanks for all of the responses guys. Sorry, didn't mean to stir up commotion between some of you there.

If the TH350 is good enough for Ski, it should be good enough for me. The easier install for the TH350 is a big deciding factor as well.

Ski, I hope I'm in that 99% you're talking about. If you are, I likely am as well. I know alot of people say the 4L60Es can be built to hold, but I see just as many people saying just the opposite.

Thanks all. I love this board because of all of the good folks on here.

0ski_dwn_it

At under 650hp a Pro-built tranny would last you forever on the street without slicks. Even with sticky tires on it, I think it would.

However if your looking into a stronger setup, then I would go the T350 route. Rossler builds some of the toughest trannies on the planet bar none. Dad just picked one up for his 555CI motor that will make over 650hp with the current heads and upwards of 800hp with aluminum heads next year. Rossler said the 350s stand up to ~1000 hp on a strip car regularly from what he has seen. Turbo and Nitrous applications above the 1000 mark, he says 400s are the ticket.

That is why I said 99% of the car on this board would be fine with a good built t350 behind their motors.

Remember for the street, trannies take much less abuse. Taking out on the strip with slicks and NO spin is devistating on clutch packs if not built right. On the street a high HP motor will just spin the wheels and unload the tranny clutches. In our 1/4 mile sprints, there is no unloading anywhere till you leave off the gas.

There is no reason you can't get a good 700r4 to live behind your application. Look at our setups and they live with over probably combined 500+ runs easily with our 406s figured into them.

Are you adjusting the TV cable correctly? That is what ruined my first stock tranny when the cable broke on a run and I did not know. Smoked it the next run.

What is failing in them. Mine was the 3-4 clutch packs.

mike 1985

thanks for posting that link. I need to learn how to do that. I'm telling all you guys it just doesn't get any easier than that.

My trans isn't anything special, just a good build with heavy duty sprag and a shift kit. I told them i was going to 375 HP motor and a 250 shot out of the box with slicks...he said no problem.