The trans are the same bolt pattern wise, if it will bolt to a SB, it will bolt to a BB. Keep in mind there is a different bolt pattern for Buick/Olds/Pontiac transmissions.

Performance wise, the T400 can handle more power, but some people like the T350 better. You may also want to think about an overdrive tranny, 200R4 or 700R4.

You'll get a lot of different opinions and suggestions, but the bottom line is what do you want to do with your car, what will it be used for, and how much HP will you be making.

 

The Turbo 400 is significantly stronger than the 350, but also weighs more (about 75 lbs). The Turbo 350 has a wilder 1st gear ratio for off the line, but the sprag is the weak spot for this tranny. I'd go with the Turbo 400. If you want overdrive, go with Gearvendors or a built 700R4 depending on the HP of the engine. Under 400hp, then the 700 will live ok.

 

A th400 only weighs about 10-15lbs more then a th350.
If you took a 11sec car and ran both trannys in it with the same converters you might get .005 difference.

 

How will I know which will fit my 69 Camaro? Is there a long and short tailshaft version of each trans? If so which will fit?

 

You would use the short tailshaft TH400 for your Camaro. The long tailshaft 400 was used in larger cars, such as Impalas, dually trucks, etc.

 

I agree 100% with what Bob has posted. The th350 is a decent tranny but, like Bob said the sprag is weak, even the performance sprags break. This is what drove me to switch to a th400.

What kind of HP are you thinking about? Are you going to drag race the car?

 

I broke two 350's in 2000 miles on my 68 with around 400 hp.

 

what about a powerglide?

 

Powerglides are good for light drag cars, with a lot of gear and stall. That would not be my choice for a street driven car. They can be built strong but, you will lack performance, in a heavy streetable car (IMO).

 

A little more info would help on which trans. is best for you.Smallblock street car will be fine with a TH350.Bob and Royce are correct about the TH400 being stronger but it is also heavier and takes more horsepower to turn it.They are running blown bigblocks too.

 

Actually mine is a blown SBC. I agree that it depends on the car and the use. I broke 2 profesionally built th350's before the blower motor but, I beat on them pretty good. The last one I broke was supposed to be "bullet proof" well it wasn't. I built my own th400 and haven't been able to hurt it yet. I like piece of mind and not having to worry on every 1-2 shift that the sprag was going to explode. Yes, the th400 is heavier and takes more power to turn. If you "need" the extra strength then it's more than worth it.

 

I really like TH-400's myself.

 

The th-350's where originally put into cars with 350 lbs of torque or less. The th400 went into the cars with more torque. So IMHO ... you have to start thinking about how much torque you are going to be making along with your Horse Power.

As mentioned above, unless you are making a wild drag car or a mild mannered numbers matching street car - The Power glide isn't really the best of options for a driver.

 

Will I be able to tell if I am looking at a short tailshaft TH400? I am thinking that unless there is a short and long side by side each other i will not be able to tell which one that I have found when i go to buy one.

I am going to either build a stroker small block or a nice performing bigblock that will push the 500HP level.

And ANY short tailshaft TH400 would work?

 

Just make sure the flange pattern ( where it bolts to the block ) is a chevrolet and it will fit. The buick/pontiac blocks are different.

The tail shaft on a short TH-400 is about 6" long and the long shaft is about 10" long. They both bolt to the back of the trans with 4 bolts and a long shaft can be changed to a short shaft with the right parts ie: shorter tail shaft and rear short housing.

 

TH400 would be my choice. You didn't mention what your motor was or it's intended rpm range. The TH400 shifts itself out of first around 6000 rpm even if you pull the shifter down into first and leave it there. You can avoid this by using a manual valve body. There may be other ways to tweak the shift points, I'm more of a 4 speed guy. But the 3 TH400 I've owned all did this and so did my brothers. He went manual valve body route on a drag car with a 302. I converted one of mine back to 4 speed and the other two were really at or above redline at 6000 rpm anyway (74Z28 with a factory L82 and SS396/350hp 70 Chevelle). The other car was a 68Z that someone had converted to a TH400, bad idea as the little 302 was just starting to make good power when the TH400 wanted to shift. I changed that car back to a 4 speed pretty quick and was much happier being able to once again wind it up to 8K.

 

As mentioned, it depends on what power levels and torque you ultimately go with, how much the car weighs, and what the car will be used for the most.

I only broke one TH350 transmission in my 3500 lb '70 Nova with a 383 stroker making about 370 rwhp off the bottle and about 510 rwhp on the spray. 11.40 car off the spray, 10.60s on it. About 200 passes and about 2-3,000 miles a year. The key was using a heavy duty sprag and a TH400 drum unit, and it lasted three 3 years and was still in good shape until I swapped to a TH400.

As mentioned by others above, the TH400 holds up to more power but you lose a little "off-the-line" gearing. I swapped to a TH400 transmission due to wanting to add a transbrake.

The old adage of powerglides not being a good street transmission is misleading. They used thousands of them in GM cars until the early 70's, but the 1.80-1.96 first gear ratio does give up a little to the 2.3-2.6 gear ratio in a three speed (or even more on an overdrive transmission). But higher hp cars like the 'glides due to a "easier" launch, and if the car has a properly matched torque converter it won't be that bad to drive.

Just my $.02

Derek

 

I know that my experience is not the norm, but I built 2 turbo 350's for my race car. It was a big block with a 250 shot of nitrous. I raced the car for 2 years and never needed the second one, and I beat on the thing hard. When I sold the car it still had the first and only 350 I put in it. This was in a 67 running 6.60 8th mile times, nitrous off the line, foot braking.

 

the drive shaft is slightly different in length from a 400 to 350. the yoke can be changed to compensate. the 400 is the best you can get, you can not tear it up and it will even shift for you if you over-rev 1st. the 700R will shift you to death around town and shifts up too fast and makes it bogg down. you can get a switch that will correct the too fast up shift but felt a little weak to me. i traded a powerglide to a 400 and before the power glide, went through 3 350's. still in car today, 396/325 horse. if available, 400 street, strip, show, etc. have a rebuilt 350 in a 68 today with the best of everthing, I would drag it across the street with my teeth for a good 400 stock. :thumbsup:

 

I have a Th350 they can be built to be just as strong as a 400 and are lighter and less powerlosses with them.

The TH400 is a great transmission to just rebuild stock and slam her in you car. She should take 500 no problem the 350 will definitely need work.

I would highly consider a 700R though because of the overdrive. I am using the TH350 and planning to get a gearvendors overdrive unit but I will have a little over 4 grand in my transmission with tc and the overdrive unit. The 700R is pretty much the same thing as the 400 just with an ovderdrive unit. It should be able to take 500hp but you might want to build it just for safety. Jay Leno believe it or not has a 700r which is the samething as the 4L60 in his tornoado with 1000hp and its a stock unit from GM I know I had a hard time believing it but the engineers assured me.

If you are going with the 700R i would not worry about anything you can get a valve body to keep you from going into low line pressures. If I was going to do a 700r I would go for the 4L60E and get an aftermarket controller. The computer assures that you are not getting into low line pressures that will burn up the clutches and gives you complete control of shiftpoints. The unit is a stand alone controller. Alot of places have them.

HaHa Irony the bottom ad right above the quick reply box was for this.
4L80E Transmissions
Computer Controlled Performance Extreme Horsepower This Will Do It
www.BowtieOverdrives.com

 

I have a Th350 they can be built to be just as strong as a 400 and are lighter and less powerlosses with them.

The TH400 is a great transmission to just rebuild stock and slam her in you car. She should take 500 no problem the 350 will definitely need work.

I would highly consider a 700R though because of the overdrive. I am using the TH350 and planning to get a gearvendors overdrive unit but I will have a little over 4 grand in my transmission with tc and the overdrive unit. The 700R is pretty much the same thing as the 400 just with an ovderdrive unit. It should be able to take 500hp but you might want to build it just for safety. Jay Leno believe it or not has a 700r which is the samething as the 4L60 in his tornoado with 1000hp and its a stock unit from GM I know I had a hard time believing it but the engineers assured me.

If you are going with the 700R i would not worry about anything you can get a valve body to keep you from going into low line pressures. If I was going to do a 700r I would go for the 4L60E and get an aftermarket controller. The computer assures that you are not getting into low line pressures that will burn up the clutches and gives you complete control of shiftpoints. The unit is a stand alone controller. Alot of places have them.

HaHa Irony the bottom ad right above the quick reply box was for this.
4L80E Transmissions
Computer Controlled Performance Extreme Horsepower This Will Do It
www.BowtieOverdrives.com

I would like to know what parts are used to build a th350 to be as strong as a th400. Do you have a parts list? I have 2 th350's I would love to build if they can be made as strong as you say. What kind of sprag did you find that is that strong? Call a few tranny shops and ask them if they can promise you this.
Sure a th350 can be built fairly strong and what usually kills them is the 1-2 shift being to hard or doing burnouts in 1st and shifting to 2nd. This is not "good" for a th400 either, you are better off starting your burnout in 2nd and just leaving it there. If you don't have the power to do that then start it in 1st and shift to 2nd as soon as the tires start to spin.

 

Like I said and some of the others have also mentioned, the TH400 will upshift way too soon for a high reving short stroke motor. Plan on a manual valve body at least as a fix to this if you go the 400 route and want to rev past 6000 rpm.

 

Like I said and some of the others have also mentioned, the TH400 will upshift way too soon for a high reving short stroke motor. Plan on a manual valve body at least as a fix to this if you go the 400 route and want to rev past 6000 rpm.

This is easily adjusted and if you are building a tranny or having one built it's simple. I would not worry about this at all. The same could be said for any automatic transmission that is not "tuned" to the combination.

 

Forgive me, I haven't owned an automatic muscle car in over 20 years, I much prefer manual trans for street cars. However I had a few TH400 and a Nova with a TH350 30 years ago. I put 6 TH350 transmissions in that Nova in a very short period of time. The next cars were TH400 cars. If I remember right the TH350 has a vacum modulator and you can install an adjustable modulator that's available in the aftermarket. But how do you taylor the shift points of a TH400, short of what my brother did in his race car by changing to a manual valve body?

Just trying to learn, who knows maybe I'll end up with another Th400 BBC car down the road.

Thanks.

 

TH400 also has a vacuum modulator. If the adjustable modulator doesn't get you the shift points needed you can recalibrate the governor.

http://store.summitracing.com/partd...g.com/partdetail.asp?autofilter=1&part=BMM-20248&N=700+-118159+115&autoview=sku

 

You can adjust upshifts by tuning the governor. Weaker springs shift at a lower RPM. There are clips you can install or heavier springs. I am no tranny expert but, I did build my current th400 with the advice and online help of Jakeshoe he used to cruise around here but, I haven't seen him on any board in a while.

I will be building the one for my Nova as well.

By the way a th400 has a vacuum modulator on it as well and you can put on adjustable ones just like you can on a th350.

 

I am no tranny expert but, I did build my current th400 with the advice and online help of Jakeshoe he used to cruise around here but, I haven't seen him on any board in a while.

Royce..I am in the market for an OD trans.Jakeshoe over at big brother Team chevelle can and will build a forward pattern,full manual non electric 4l80 with lock up feature that will survive behind my blown big block.He thinks my current tci 700r4 even with the constant pressure valve body is living on borrowed time.For the original poster..I would seriously consider the overdriven non ecm controlled 4l80 for a street/strip car.The strenght of a th400 without the failure of the 700r4.I posted in team chevelle trans about the tci cpvb and Jakeshoe recently advised me.Hope this helps.

 

Thanks guys! I'm always happy to learn something new. I've avoided auto trans for years, so please forgive my ignorance about them. But maybe it's time to step up to a BBC with a TH400 behind it now. Thanks again!

 

The TH350 can be built strong no doubt, I do not have a parts list but it did cost me over a grand in parts alone. The downfall of building a strong 350 is the cost associated but if you look at how much people spend on an all roller 400 I don't understand why not put the money in a 350.

It's just like the 4l60 and the 4l80, the 4l60 can be built just as strong if not stronger than the 4l80 i know a few cars with 4l60's and 1000hp +.

 

The TH350 can be built strong no doubt, I do not have a parts list but it did cost me over a grand in parts alone. The downfall of building a strong 350 is the cost associated but if you look at how much people spend on an all roller 400 I don't understand why not put the money in a 350.

It's just like the 4l60 and the 4l80, the 4l60 can be built just as strong if not stronger than the 4l80 i know a few cars with 4l60's and 1000hp +.

If you say so but, I haven't seen it yet. You can build a th400 that will hold 750-800HP for less than $500 in parts if you know where to shop. It will cost you at least double that to build a decently strong th350. I paid over $1200 for my "bullet proof" pro built th350, I broke it with about 475HP it lasted about 8 months on the street with maybe 10 passes at the track. I then built the th400 (home built) it lived through that engine, I then built a blown small block and stuck that in front of the th400, it is still alive and well. That is first hand experience. I am a rookie tranny builder so imagine what a pro can do with a th400. You just don't need to do anything special to make a th400 strong it is already strong, A better drum and clutches a few pressure mods and you have an instant monster of a tranny.

I am not going to say a th350 can't be built very strong, I just don't understand why you would spend double and have a tranny that is still questionably as strong as a decent built th400? The difference in weight isn't big enough to offset the cost (IMO).

I would like to know what the th350's that are stronger than the th400 are using for a sprag. Does anyone know? Is there some new super sprag out there? If there is a new super sprag out there I "might" be willing to repair one of my broken th350's and give it another shot.

Once again I am no tranny guru so, maybe I am wrong. I just would like someone to show me the light. A parts list would be nice or a modification list to make a th350 stronger than a built th400. All the tranny shops I consulted with said the th400 is the better choice if the car is heavy or making big power/torque.

 

I completely agree with Royce. The TH400 is such a beastly strong transmission in stock form it is very tough to break. Take a look at the stock cast sun shell in a TH350 vs. that battleship armour of the TH400 shell, and it quickly becomes apparent how much larger and beefier the parts are in the 400 vs. a 350 and why they have such a solid rep for reliability and durability.

I have ran a TH400 for the past 6 years behind two 11-second street 400 small blocks in my heavy 1977 Z-28 Camaro. I paid $75 for it used, out of a core yard. I was told it came out of a 1-ton truck. All I did was pull the dipstick, the fluid looked and smelled okay, so I bought it. I then put a $30 B&M shift kit in it. So for around 100 bucks I've had a tough, strong transmission which I've proceeded to beat the crap out of on the street and with many passes at the track over the past 6 years or so. My last outing at the track on Friday night, I noticed the transmission was flaring on the 1-2 and 2-3 when shifted manually, and the shifts are not as crisp or timely as they used to be, so now I'm going to have it rebuilt and throw it back in. Even with those issues, it still enabled me to run a few 11.90 passes on drag radials right off the street on pump gas. Bang for the buck, it's very difficult to beat the TH400. Maybe it takes a few more ponies to turn than a TH350, but so what. The trade-off in my favour in terms of dead-nuts reliability, the capacity to take a pounding, and handle a high-HP and torque engine in stock form is worth it by far, in my book.

 

Yes, I am not saying for the money the 400 isn't the winner. I am saying that if you are willing to spend a bit of money you can build a great 350 in fact I know a few guys that used to build 350's for alot of chevy circle track racers. They can be built strong all the components that are weak can be replaced. A pro vs a rookie in trans building can be huge in performance of trans if clearances aren't right and so on.

I do know I have an upgraded sprag and drum set although I don't believe there is a sunshell in the th350 no overdrive in it and no need for one with a clutch to band transmission. I also have about 4 extra clutches for my foward gears and 3 for my reverse. Which basically is the difference between different power rated transmissions.

The new transmissions 6 speed automatics that is the only difference between trans's really are extra clutch packs. If you beef up the carriers and sprag and add clutches the trans is much stronger.

 

I don't believe there is a sunshell in the th350 no overdrive in it and no need for one with a clutch to band transmission.

Both the TH400 and TH350 have sun shells, the input planetaries sit inside the sun shell.

 

Radcannon,
By all means stick to what works for you. I would never try to change someones mind. For giggles I went out on the web and tried to see if anyone was offering a guarantee on a "race" or "performance" th350 tranny. Most sites didn't even offer a th350 for racing and the one I did find only rated them to 550HP max (non supercharged) and I didn't see a warrantee. While the same site rated their th400 at 950HP.

I was trying to support what you were saying about the th350's I just couldn't find anything out there. I know some shops will tell you anything to make the sale. I fell for it once. You can also upgrade the drum and add more clutches to a th400 which is one of the basic mods to make them hold more power.

There is a "super" drum for the th350's which my broken one has. It's the sprag that is the major weak link in th350's. I would bet 80% or more of the failures in "built" th350's is the sprag. The hard 1-2 shift kills them. Last I checked (about 4 years ago) there wasn't anything out there to help with this issue. Yes, the roller sprag helps but, I have that too in the broken tranny and it's the sprag that's bad.

 

I'm around still but I don't frequent as many boards as I used to.
Honestly trying to put good information out there while dealing with all the "experts" arguing with you have never even rebuilt a transmission gets old.

A TH350 will never be as strong as a TH400 simply because of it's design. That said, I will warranty my units up to 800 HP in racing applications. IMO this is the limit of the TH350 due to it's planetary design. They just don't have the strenght above this level. I think that if you are purpose building a car and picking a GM 3 speed, the TH400 should always be selected at over 500 HP/TQ, but if you have a stout car and it already has the TH350, just upgrade it to handle the power.

Just to clear a few things up...
A TH350 weighs 125 lbs, short shaft, without converter, dry.
Same specs TH400 weighs 134 lbs.
That isn't 75 lbs by my calculations.

A TH400 doesn't have a sun shell. This is a major reason the TH400 is a better choice for a transbrake application.

I use 36 element sprag and drums for the TH350. These help tremendously with sprag failures in the TH350. I have never had one break in a unit I built. I have warrantied ONE drum assembly to a customer who built their own trans and it broke several months later.
I am making these drums, and they are similar to the pieces offered by other major manufacturers.
The TH350 outer race doesn't have as much cross section as the TH400 piece, so without using a redesigned race and intermediate clutches, I can't get away from that, but as I stated, failures are rare.

The 1-2 shift must be kept within reason on both units, but especially the TH350 because of what I stated above.

I was looking at using a mechanical diode style setup on the TH350 drum but others have already tried this and it wasn't as successful as expected according to some.
I may still try it for giggles.


Royce,
I'm glad your TH400 is still working great for you. If you are interested in putting together one of your TH350's let me know. You'll like the drum assembly.

Jake

 

Just to clear a few things up...
A TH350 weighs 125 lbs, short shaft, without converter, dry.
Same specs TH400 weighs 134 lbs.
That isn't 75 lbs by my calculations.

Yes, I corrected that comment. I was thinking of a 'glide versus a TH400 when saying there was a 75 lb difference.

 

The HD sprag works just fine IF you have proper shift timing. I'm with Jake on this... a well-built TH-350 can take some serious abuse.