Hot Rods 400 turbo vs 350 turbo

I got into a discussion with a friend of mine over power loss from a 400 vs 350 turbo. He says on a chassis dyno a 400 is 75 hp less than a 350. I say bs. What say all you transmission guys?

 

I always heard 15 HP.

 

Found this

 

Plus the 400 is heavier by 15 to 20 pounds

 

For simplicity of operation it's hard to beat the TH400. Good for hauling, towing and overall durability. Good choice if you're not worried about a little extra weight. If you're concerned with lighter weight and maybe shaving a tenth or a few hundredths off your 1/4 mile times a prepped TH350 might be a better choice.

 

i was looking for either when the 4oo popped up, so went with it. i have had a bone stock 400 in my 39 for over 20 years. not one problem. they are a tough transmission.

 

Would love to see how a Borg Warner Auto or a Hydromatic compare!

 

These Older Pg 350's & occasionally 400
Stock Bells are getting Brittle ,
Not from average torque though ,

 

Did several deuces in the 70's with 400's then switched to 350's because of availability. Currently doing a new 32 roadster with a 400 to closely duplicate one I built in 1978-9. For got how big they were. I remember they seemed to be bulletproof.?

 

I don't think there's a tougher more reliable auto than the 400. Want more? 34 element sprag, bearings vs bushings, all of which may just be ¾-1 ton truck internals. It'll last forever in a car, for years in a racer. I sold mine with a Hipster transbrake and the stuff above, had about 300+ rounds of racing. He said he was gonna freshen it up. A cpl months later I'd seen him and he said he didn't have to do anything to it. My convertor was a 5,000 stall Continental. My car weighed 3545 with me n fuel so if they hold up like that...? Can you tell I like em

 

Turbo 400 is my favorite Trans too.

To me well worth anything that it might add over a 350 to the car (15 lbs ? 10 more horse loss) I'm fine with that.

....

 

Pulled a th475 out of a motorhome.
A HD 400 with thick case and straight cut gears
Got it in my future build pile.

 

I’ve got a TH400 in my coupe and it’s a great transmission that outlive us all, but… it’s not a good combo with the other driveline components. That tall first gear plus my 3.08 ring and pinion makes it a dog, but a good road car. I have a fresh 700r4 but that would require moving the trans mount several inches forward.

motor is a mildly warmed over 9:1 327

I’d rather do a 3.73 rear and a gear vendors with the TH400 but I doubt I’ll ever be able to afford that.

 

Th475 with Doug Nash OD
Test fit, used a regular th400 that was already in my ride.

 

I’ve had my eyes peeled for one of those for years. Must be kinda rare.

 

I guess. It popped up on FB. Drove 4 hours to pick it up.
It’s a simple set up. I’m using a 2 speed rear end switch and wiring. Let off the gas and pull up the switch. Bang. It’s in OD

 

As a general rule of thumb, I avoid things that "poop" up. Normally they are shit.

 

Well I bout pooped my draws when I found it

saved me from doing a 4l80 swap

 

I will keep my eyes open.

I seem to find them all of the time, in both the overdrive and underdrive versions (+20%/-20%)

The design was eventually sold to US Gear, so look for those, too

 

HMMM not the dream I had, running freight in vans with a lead foot and a 'beat the clock' attitude. My favorite trans guy never heard of me 'til I saddled up on the 400TH
@anthony myrick Nice set up have there. I'm sure you'll do right by each other.
I just was just a demon trying to make a wad of money for cheap pay.

 

The guys who say you lose some number of HP in a transmission...how do you figure? Seems to me it's a percentage. Because I know that when I have my engine idling, making no HP at all, and put the TH400 into gear and the car starts moving, I'm not losing 75 hp in the transmission.

 

like the chart though ya just bummed me out with the C6 numbers.. I was planning on building roughly 600 hp for the F100 and figured on loosing 20-30% in drive line which would make the 65 look good but now I really want solid numbers to base the build on.. Now I'm gonna overthink this for way longer than I should..

 

It's funny to hear about a "Heavy Duty" version of a TH400... as if they aren't already heavy duty!

 

haven't done that yet but have definitely cracked a few 400's right at the 2nd gear clutch pack breaking the teeth out at the snap ring . last two broke clear through leaving a little window on top the case

 

X2!!

 

I've heard 40hp. On the 400..

 

Rebuilt a lot of Th475s back in the day for a uniform rental company, that were in their step vans.
Still have planetary gear sets for them.
You think a Muncie M22 is noisy? Wait till you put a 475 in a car. The "boom box in the trunk has trouble drowning out the gear whine in 1st and 2nd!

Bill

 

That’s music on its own
Love those gear sounds

 

HD only in terms of light duty rides.
the th400 was known for cracking bells.
Friend busted several in his step van.
If the th400 was a real “HD” trans, Allison wouldn’t have a reason to exist

 

I would think it's only a percentage up to a certain point, hence the guys quoting a fixed hp number. Say you've got a 300hp engine and for the sake of argument let's say the trans is taking 20%. OK, 60hp loss. So the same transmission will now rob 120hp on a 600hp engine?