Th350 vs th400

[tiguido]

What are the differences between those transmissions ? thx

 

[cntrhub]

The 350 is a 3 speed, and of course is a little smaller in size, (approx. 3'' to 4'') because it has one less clutch pack than the TH400. Basically, one is a 3 speed, the other a 4 speed. Thus, the designation of the names. There are arguments by aficionados as to which is the best. 3 speeds will work up to 325HP. The TH400 will accept a higher output engine.

 

[MaineShark]

The TH350 and the TH400 are both 3-speed automatics.

The 4L80E is a 4-speed that is based on the TH400 design, but it is a separate transmission and is only used in trucks.

Joe

 

[Eric]

Maineshark is right, they are both 3 speeds; I'm guessing the "4" threw him off and make him think of the 700R4 that showed up a little over 20 years ago.

The TH400 is a beefier tranny that the TH350, handles more torque than a TH350. Back in the infancy of 3-speed autos, all Vettes got the 400, but the rest of the fleet got the 350 unless it had a big block, LT-1 or other high power engine.

Though nothing is 100% indestructible, many refer to the TH400 as bulletproof.

I'm sure some of folks more experienced with the engineering aspect will chime in with the specifics of why the 400 is the beast of the two but for now here are the ratios along with the 4-speed autos:

Transmission Ratios
1st / 2nd / 3rd / 4th
TH350 - 2.52 / 1.52 / 1
TH400 - 2.48 / 1.48 / 1
200 4R -2.74 / 1.57 / 1 / 0.67
700R4, 4L60(E) - 3.06 / 1.63 / 1 / 0.7
4L80E - 2.48 / 1.48 / 1 0.7

 

[C3forME]

The TH350 also has a lower 1st gear ratio than the TH400.

 

[Jacko]

Let me EDIT this message and apologize. The more I look at it, the more I don't like what I wrote.

QUOTE :
The 350 is a 3 speed, and of course is a little smaller in size, (approx. 3'' to 4'') because it has one less clutch pack than the TH400. Basically, one is a 3 speed, the other a 4 speed. Thus, the designation of the names. There are arguments by aficionados as to which is the best. 3 speeds will work up to 325HP. The TH400 will accept a higher output engine.

REPLY: EDITED and my sincere apology to MainShark.

The TH350 will handle a whole LOT more than 325 hp.
Also, it is much lighter than the 400 tranny. You lose 10% hp all things equal, with the TH400 vs. the TH350 in a 3500 lb. car.
That is due to the extra effort required to turn/move all the heavy internal parts.
And you can ADD an additional clutch if needed, along with better material.
I run one and it works!!!!!!! and it works GREAT !!!!!!!!!

Once again, I am sorry if I sounded rude. My reply was un-called for and meanspirited.
I am not my normal self lately. I have been sick for some time now and I am undergoing chemo-therapy treatment and the drugs cause some strange side effects.

I wish you all the very best for the holidays.
Jack

 

[cntrhub]

Well, I looked at a few websites that exclusively build TH type transmissions, and this is where I got the information. I was thinking 700R 4-sp. I'll research more accurately next time. Sorry for the misinformation. My apologies.

 

[Bob Chadwick]

We all make mistakes.

 

[Eric]

Play nice everyone, no need to be negative.

Eric Whitaker
CAC Community Administrator

 

[Rob]

The purpose of these forums is for people to learn about the Corvette. It's obvious that some people are going to know less than others and as a result, they're going to come to the table with inaccurate information.

Rather than crucify them for their bad information, simply provide them with the correct information and cite your sources.

 

[Jacko]

Well, I suppose you are suggesting that I "crucified" someone.
If it came across that way, I am sorry.
I did not mean for it to be that way.
Merry Christmas in any event.
Jack

 

[AKRAY4PLAY]

Jack,
you don't loose 10% of your power with a 400 vs a 350. it is more like 10 hp. basically speaking they are almost identical in design, the old school drag racers were the ones that pushed the 350, saying that the 400 zapped a bunch of hp. the reality was the difference in first gear ratio. Merry Christmas to you to, as well as everyone else!! Brian

 

[Jacko]

Akray4play, I am sorry to disagree with you, but the facts are accurate that I quoted. I said 10% and I tried to be conservative.
It is actually 10-15%.
The following quote below is direct from Novak Conversion's website. See for yourself.


TH400's do not convert well into 81" and shorter wheelbased Jeeps. The exception is if a V6 is used and moved forward in the engine bay. However, a V6 and TH400 is not the best combination, as 12-17% of the engine's power is consumed just to run the transmission. The more efficient TH350 would be the automatic of choice for such a swap. However, the TH400, coupled to a strong V8 in a CJ7 and longer Jeeps, is a fine choice for a conversion. If you have any questions about planning around such issues, feel free to give us a call and see if we can assist you.
http://www.novak-adapt.com/knowledge/th400.htm


And Merry Xmas to everyone here at CAC
Jack

 

[AKRAY4PLAY]

Jack,
we agree on the point that the 400 sucks a little more power than the 350. your refference states that the 400 takes 12-17% of the engines power to turn it. now i point out that they talking about a V-6 engine. i ask, what V-6?? is it a Buick 231?? Vortec 4.3L?? Amc ?? what was the power rating of that engine?? what % of the power is required to turn the TH350??
the point i am getting at is there is no base from the angle Novack is working. you can't make % statements without supplying HP figures. you could look at like this, my 406 makes 600hp and i'm running a TH400, John Doe is running a 350 making 200hp mated to a TH400. i seriously doubt that the TH400 in my car (sucks 60hp) and the TH400 in John Doe's car (sucks 20hp) are different. this is going from your stated 10% to make figures easy. see were the % thing goes wrong?? the tranny only "drains" a certain amount of hp, not a %. and where is the drain that a TH350 has posted?? i know a TH350 is not friction free.
i read about the TH350 on their stie, and no mention of the power needed to turn it. if i was a betting man, i would guess that the TH350 required 10-15% of that peticular V-6. Brian

 

[tazdevl35]

Just FYI the turbo 350 and turbo 400's first gear ratio can be changed by using a different plantary for first gear without changing second and third. Parasitic drag(loss of horsepower) is caused by the front pump converter ,and and other reciprocating parts in the trans. The 400 is a bit bigger and has heavier internal parts. As a point of reference a turbo 350 can be built to be as tough as a turbo 400 using a better sprag, hardened shafts,upgraded pump assy and such so if horsepower loss is an issue, I suggest going this route. However ,building it with heavier parts will cause more parasitic loss than a stock TH 350.It always worked for me in the transmissions I have built for my own cars.I also use a case saver to keep the inside of the case of the TH 350 from being damaged in higher horsepower applications.Making sure the tolerances on the clutch packs is a bit closer than oem helps too as well as better clutches and steels, better band and better servo and accumulator as well.


Taz:bang

 

[Jacko]

Here are some power loss estimates:

If memory serves me the TH-400 takes approximately 45 HP, the TH-350 uses about 30HP, and the PowerGlide/JetAway uses about 20HP. It is possible to pick up nearly two tenths by switching to the TH-350 behind a 327 c.i. motor. I attribute this to 3 things:


1) the 350 weighed less.
2) the 350 has a slightly lower first gear (2.52 vs 2.48).
3) and finally the supposed HP loss difference.

The differences in loss also seem plausible when considering the size (mass) of the internals on each of these transmissions.
And what is the percentage difference? 15%.

The TH-350 will handle in exccess of 550 lb ft of torque if built right. I have used one for 5 years with NO failure of any part. Keep the fluid changes to 12,000 miles, and put an auxilary cooler on it. As a note it takes approximately 14-18 less horsepower to turn the TH-350 compared to a TH-400. So you are freeing up some horsepower. It also has a slightly lower first gear.

The 350 was the transmission of choice for drag racing up to about the late '70s as it was easy to build up strong. The TH-350 was the tranny of choice for drag racing because it has less internal mass and weighs less initially. But, for the same reasons, it is not as strong. The TH-400 and TH-350 use the same converter.
[ Thanks to Steve Ochs, Jack Wendel, Jim Chermack, John Pajak, Joe Padavano, Dave Wyatt, Greg Beaulieu for this information ]

 

[AKRAY4PLAY]

now that we are on the same page, let's have a beer. Jack as you stated, it takes 15 more hp to turn a TH400, i said 10, close enough for government work. i agree on the times of TH350 vs TH400 at the strip. i only said that the parasitic loss is not as bad as what was previously stated. granted a TH350 can take punishment when built right.
it all depends on the eyes of the end user.
1. need a strong tranny- budget is more important than performance, TH400 wins.
2. need a strong tranny- performance is more important than budget, built TH350 wins
3. don't care about reliability- performance higher than budget, TH350 wins
4. don't care about reliability- budget higher than performance,
either tranny wins, but you may be walking!!!
5. absolute reliability needed- performance higher than budget, build a TH400
for me a TH400 is the better tranny, i don't race for a living. i want the ultimate in reliability and i'm not affraid to spend a little money or give up a couple ponies to get it. when i was building my car, i talked to all the racers and got the name of the best tranny guy within 300 miles of home. i emailed him a dyno sheet and figures on the car. he said a TH350 would work, but could not testify it would last. he swore on his eyes that the TH400 he built me would take 850ft/lbs though. so that is what i got, and i hammer it with 588 ft/lbs as often as i can. after three years the fluid is still clean and she ain't leaking a drop. the only complaint i have is getting my head slapped into the rear window every time i shift with WOT. Brian

 

[Jacko]

I agree with you 100 %.
And a cold beer would be great (but it's only 8:00 AM)
so we have to put it off for a few hours.
But I will buy.
Do you want to head on over to the strip Club
or the local joint?
Have a great holiday,
Jack

 

[74bigblock]

I speak opnly for myself here... but all this talk about TH350/400 trannys being put into jeeps and correlating this with Vettes is camel dung. I've got a 400 in my Vette, It came from the factory like this... therefore I will never swap it out. So you say it sucks 45p? Fine... Considering my motor is pushing out about 450HP... I figure I still have at least 55 HP on all you 327 folks, plus one Bad A** sounding ride. I'll let you all know the exact HP rating as soon as Hooker decides to send my new headers back to me.

 

[AKRAY4PLAY]

Dave,
we were simply trying to describe the real world eff numbers of TH350/400 in any vehicle. it took at little bit for everyone to see the big picture, but it happened! i would be intersted in getting some info on your big block. i am always curious to see what other's are running for performance upgrades.
Jack,
let's hit them all!!! ain't nothing like throwing money away on strippers first thing in the morning to get your day rolling. and it is never to late or early to get a beer. in the old west (and Mexico now-a-days) you have to drink beer all day, the water will kill ya. Brian