turbo 350 vs turbo 400

[jbk240z]

Let's not get too technical here. I have always heard that a T400 takes more power to turn Than a T350 as well. I have known people to swear by this, but none of them or myself have half of the knowledge and experience that dr_hunt or jakeshoe and others here on HybridZ have. That is why I love to hang out here on the premier Z site.

 

On another note, do either of you know if a 350 crank will fit a 283?

 

Just kidding guys.................lol!

[Mike kZ]

This is a great thread, keep it technical! I have heard that there isn't much of a difference between the T350, and T400 until you get into the 8's and 9's

[dr_hunt]

Well, you kind of got it figured out already, the TH400 internals are heavier, therefore if it goes from zero to 120mph, going through 3 gears, it will take more HP to accomplish that than a th350 and a powerglide.

 

How much would have to be tested on a dyno. Kind of pointless, though, splitting hairs, 15 to 25 HP difference isn't that much in the big scheme of things when you consider a manual trans uses even less HP, but an auto is typically quicker since you don't have interruptions in power to the rear wheels.

 

I've heard the same, seen some 9 second cars pick up some time going to a glide from the th400.

[Guest Indy]

Wow, tons of info. Thanks for the replies. But could we dumb things down a bit for me. Specifically I'm building a cruise around town but want a bit o'power now and then car. I don't have anywhere nearby to drag, so as much as I would like to I can't.

 

I have a '78 280z w/a stick, that right now is a big chunk of rust but has dreams of a VR body kit and a v8. I finally found a guy nearby that has both a couple good 350's and a couple good tranny's, a 350 and a 400. I'd prefer a stick, for an auto I'd prefer an OD. But at the same time I really really want to start working. The car has been untouched for over a year now, and I figure I can swap a stick back in later if I really want to.

 

The engines are mid 70's which I think are less than ideal. But I think they'll be fine to start with and I can build more power later on. In all likely-hood 300-350hp is the max I would ever see. I don't have the funding to spend more.

 

So for my setup, are there any advantages/disadvantages to either trans?

 

Thanks again for all the replies.

[Mike kZ]

Where is Omicron Persia 8? If your car is a " big chunk of rust " you may want to look for a better car for a V8, unless there just isn't any where you're from.

I would go with an OD , stick or auto. If your only choices are a T350 or T400, I'd go with the T350. It's lighter, and shorter, and if down the line you want OD, a 200-r4 is the same size.

[Guest Indy]

Thanks, that's what I'm looking for.

Most of the rust has been or will be removed. Around the wheel wells and the like that my plasma cutter is going to fix for the new body anyway. It's more ugly than structurally unsound. I've been looking for quite a while for a workable engine/tranny combo, and I can pick this up for less than $500. I'd like newer/better, but the budget only goes so far. Down the road i can stroke the engine and put in a 5 speed. But I'm sure I'll have fun for a couple years as is.

[Lason]

Where is Omicron Persia 8? If your car is a " big chunk of rust " you may want to look for a better car for a V8' date=' unless there just isn't any where you're from.

I would go with an OD , stick or auto. If your only choices are a T350 or T400, I'd go with the T350. It's lighter, and shorter, and if down the line you want OD, a 200-r is the same size.[/quote']

 

Actually the TH350 and 400 came in different length tail shafts and are about the same size. A long shaft th350 is the same length as a mid length th400.

 

 

http://www.tciauto.com/tech_info/trans_dims.htm

 

That being said the tranny mount is moved back a few inches on the TH400

[Scottie-GNZ]

Great thread!!!

 

I too was concerned about all the Internet info about weight and HP loss. My drained TH200-4R was less than 10# lighter than the TH400. Marginal, considering the location in the chassis. As for HP, if my engine is using more power to drive the TH400, then Shhhhh, dont let it know :D For sure, big HP cars (especially forced-inductions) will actually benefit from the gearing, one of the reasons why turbo cars should not use the 700. What is puzzling to most is how a lower numerical overall gearing can make a car accelerate quicker. My best example of this was 240Z Turbo who used a JATCO for a while and switched to a Glide and with no other changes went from 11.1s to 10.6. In theory how could a tranny with a 1.8x 1st gear make a car accelerate quicker than one with a 2.8x?

[Lason]

Great thread!!!

 

I too was concerned about all the Internet info about weight and HP loss. My drained TH200-4R was less than 10# lighter than the TH400. Marginal' date=' considering the location in the chassis. As for HP, if my engine is using more power to drive the TH400, then Shhhhh, dont let it know :D For sure, big HP cars (especially forced-inductions) will actually benefit from the gearing, one of the reasons why turbo cars should not use the 700. What is puzzling to most is how a lower numerical overall gearing can make a car accelerate quicker. My best example of this was 240Z Turbo who used a JATCO for a while and switched to a Glide and with no other changes went from 11.1s to 10.6. In theory how could a tranny with a 1.8x 1st gear make a car accelerate quicker than one with a 2.8x?[/quote']

 

Well you can leave harder without having to worry about blowing your tires out from under you which is a big reason Im running one. Second reason is with only one shift you can stay into the upper rpms and boost longer and only have to shift once. Also the internals are lighter (which Im not going to argue the effects of that again, lol) and the overall weight of the 'glide is lighter. As long as you have somewhat of a light car that can handle a 1.76/1.80/1.82 first gear and not fall on its face then your good to go.

[jnjdragracing]

Hey Scottie,

 

Great thread!!!

 

In theory how could a tranny with a 1.8x 1st gear make a car accelerate quicker than one with a 2.8x?

 

It is called Horse Power baby.....

 

Remember we went from a TH350, breaking to many parts, to a PowerGlide. Then we went from a 3.70 gear ratio to a 3.54 and picked up even more ET and Speed.

 

John

[jnjdragracing]

I agree, only have to shift once.

 

John

 

Well you can leave harder without having to worry about blowing your tires out from under you which is a big reason Im running one. Second reason is with only one shift you can stay into the upper rpms and boost longer and only have to shift once. Also the internals are lighter (which Im not going to argue the effects of that again, lol) and the overall weight of the 'glide is lighter. As long as you have somewhat of a light car that can handle a 1.76/1.80/1.82 first gear and not fall on its face then your good to go.

[jap tin]

A loose converter and a low rear gear always helps. My glide has a 1.89 first and with a 4.86 rear gear along with a 6100 rpm launch will get you 1.16 60ft. times.

[jakeshoe]

Actually the TH350 and 400 came in different length tail shafts and are about the same size. A long shaft th350 is the same length as a mid length th400.

 

 

http://www.tciauto.com/tech_info/trans_dims.htm

 

That being said the tranny mount is moved back a few inches on the TH400

 

Gonna have to correct you here, you started out right, a TH350 and TH400 are about the same size,

A SHORT SHAFT TH350 and a short shaft TH400 are almost identical in length. I believe the difference is about 3/8".

The mount on a short TH400 is 6 3/8" further rearward than a TH350.

 

SOMETIMES you can use the same driveshaft on a TH350 - TH400 swap, I have been able to do it before. sometimes it will not work because of the yoke design.

You have to change the yoke anyway, but GM used several different length of yoke on the TH400's.

 

A 200-4R is almost exactly the same length as a TH350 and TH400., It will use a short shaft TH350 yoke and driveshaft, and the crossmember in the TH400 location ~6" rearward.

 

I'm actually installing a 200-4R in the 260Z tonight.

[Lason]

Gonna have to correct you here' date=' you started out right, a TH350 and TH400 are about the same size,

A SHORT SHAFT TH350 and a short shaft TH400 are almost identical in length. I believe the difference is about 3/8".

The mount on a short TH400 is 6 3/8" further rearward than a TH350.

 

SOMETIMES you can use the same driveshaft on a TH350 - TH400 swap, I have been able to do it before. sometimes it will not work because of the yoke design.

You have to change the yoke anyway, but GM used several different length of yoke on the TH400's.

 

A 200-4R is almost exactly the same length as a TH350 and TH400., It will use a short shaft TH350 yoke and driveshaft, and the crossmember in the TH400 location ~6" rearward.

 

I'm actually installing a 200-4R in the 260Z tonight.[/quote']

 

Then please contact TCI and tell them they are wrong since you know everything about trannies. THEY say a long shaft (12" shaft) TH-350 is 33 27/32" just like the Th400 with mid length shaft (about 9" shaft). That is why I included the link.

[jakeshoe]

TCI's website is a good reference and fairly accurate.

 

let me ask you a question here, you seem to be distrurbed that I am correcting you.

 

First,

We have a potential audience of thousands of other enthuisiasts.

You are trying to help them by posting information, however if you post incorrect information you haven't helped and have potentially cost them more money.

I have alot of experience as a mechanic and hotrodder. Several years of experience working in private shops or dealerships. I currently work for an OEM automotive manufacturer.

I also have quite a bit of automotive machining experience.

I'm certified by ASE as a Master Auto Tech and Master Gasoline Engine Machinist, my master auto tech is a recert, so I've been certified for almost 10 years now.

I would be considered an automotive repair expert by most people. However there are still people out there who know alot more than I do, or alot more about certain aspects of autos.

My "specialty" or what I concentrate on now is mostly GM automatic transmissions for high performance applications. This is what I do as a "hobby" and side business. So yes I do know a little about the subject we are discussing.

 

Now back to the specific discussion we are on,

We are dealing with Datsun Z cars that have a fairly short wheelbase.

My 260 with JTR mounting and a SBC/ short shaft TH350 combo has a driveshaft center to center length of 22". That's pretty short. Nothing wrong with a short driveline but you can start to have issues if you get too short, driveline angles.

I wouldn't recommend using a mid or long length transmission in the Z car unless you had a specific reason for doing so and know how to properly set the driveline angles.

[Lason]

I have no problems being corrected but when I have solid data to prove what Im saying then I dont see how come you keep trying to correct me. Its a little belittling to tell ya the truth. Now, have you sent TCI that email yet? I would be very interested in reading their response to you.

[Michael]

For a rotational system, power is torque times angular speed. The power dissipated in spinning a transmission comes from two parts: that necessary to change the rpm (when accelerating), and that needed to maintain a steady rpm.

 

The former goes as moment of inertia times rate of angular acceleration times angular speed. This is where spinning “big stuff” takes more power. The latter goes as force (as in friction) “times” (actually cross product) a moment arm times angular speed.

 

A transmission with lots of big, heavy parts (technical terms here!) does not necessarily absorb lots of power when maintaining a constant rpm, but it will absorb lots of power to spool-up. Whereas a transmission with "light" parts might nevertheless absorb lots of power in cruise, if it has a lot of internal friction acting between surfaces at high relative rotational rates.

[jakeshoe]

I have no problems being corrected but when I have solid data to prove what Im saying then I dont see how come you keep trying to correct me. Its a little belittling to tell ya the truth. Now, have you sent TCI that email yet? I would be very interested in reading their response to you.

 

You are probably correct on the lengths for the Long tail TH350 and mid length TH400, however try to find a 13" tailshaft Th350...they were rare to begin with, now after being out of production for 20 years, they are virtually impossible to find. I actually don't believe I've ever seen a 13" tailshaft TH350 in my 14 years of rebuilding transmissions....

And as stated earlier you wouldn't want to run that long of a tailshaft in the cars we are speaking about for driveline angle reasons.

 

A short shaft Th400 and Th350 are approx 5/8" different, I measured tonight to refresh my memory.

[jakeshoe]

[jakeshoe]

Pic above, TH400 is on top, short shaft, Th350 is the lower unit, also a short shaft.