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Weird problem with TH400 (see post #79)

I think if you had a new 700 built right you wouldnt hate on it so much. Just sayin, they get off much quicker. I can waste my buddies $4000 383 with th400 and np241 in 4lo off the line with my $1200 motor and built 700 and in 4hi to boot. That first gear is just soooooo long.
 
Deuling said:
I think if you had a new 700 built right you wouldnt hate on it so much. Just sayin, they get off much quicker. I can waste my buddies $4000 383 with th400 and np241 in 4lo off the line with my $1200 motor and built 700 and in 4hi to boot. That first gear is just soooooo long.
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So a slightly lower first is the only reason to run an inferior transmission? For the money you'd spend buying a 700r4 that might survive you could build a bulletproof 400 or a decent 4l80e.

I've got a love-hate relationship with the 700. My K5 had one, had it built with good parts at a local place. Truck had 33x12.50's and 4.10 gears, drove it back and fourth to school. Trans failed in under a year. My Syclone has a 700 thats bone stock except a 3200 stall and it took the abuse from a built motor and big turbo all day everyday without a whimper.

I think the 700 is great for stock rigs and fast cars (because of the smaller size and lighter weight) but if you're building a truck to abuse why not use a trans that was designed for severe duty to start with?
 
Glad to hear its working out for you!

Deuling, That was a stupid argument. Want to compare something, do it apples to apples. Some things about 700r4's are better than th400's and the opposite is true as well.
 
Cruz89K5 said:
So a slightly lower first is the only reason to run an inferior transmission? For the money you'd spend buying a 700r4 that might survive you could build a bulletproof 400 or a decent 4l80e.

I've got a love-hate relationship with the 700. My K5 had one, had it built with good parts at a local place. Truck had 33x12.50's and 4.10 gears, drove it back and fourth to school. Trans failed in under a year. My Syclone has a 700 thats bone stock except a 3200 stall and it took the abuse from a built motor and big turbo all day everyday without a whimper.

I think the 700 is great for stock rigs and fast cars (because of the smaller size and lighter weight) but if you're building a truck to abuse why not use a trans that was designed for severe duty to start with?
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An SM465???

If I was going to run an inferior transmission (read "automatic") I would run a TH700R4, or a TH350, a TH400 would be my least desirable option.

Martin
 
82355 said:
An SM465???

If I was going to run an inferior transmission (read "automatic") I would run a TH700R4, or a TH350, a TH400 would be my least desirable option.

Martin
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Touche, sir. While I'm a big fan of the sm465 and 4 of my 7 vehicles, including my current DD and tow rig, have had manual transmissions I've just never desired a manual trans in a wheeling rig despite the gearing benefits, simplicity, and brute strength.

Being that I nearly always find myself agreeing with what you Nebraska boys have to say, I'm inclined to wonder why you wouldn't want a th400, aside from it not being a manual.
 
What my transmission guy said is that t400s while being strong as h3ll, just waste so much power to turn them that he said he can build a 700 (built mine for $500 out the door) to take the abuse, and the gearing is just so much better. But also this is coming from a guy that used to build drag cars so all they cared about was get up and go. I like the same thing for in the dunes, i dont wanna waste what power i have to get me going.
 
Cruz89K5 said:
Touche, sir. While I'm a big fan of the sm465 and 4 of my 7 vehicles, including my current DD and tow rig, have had manual transmissions I've just never desired a manual trans in a wheeling rig despite the gearing benefits, simplicity, and brute strength.

Being that I nearly always find myself agreeing with what you Nebraska boys have to say, I'm inclined to wonder why you wouldn't want a th400, aside from it not being a manual.
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TH400's are too big. Too much parasitic loss. The only use for them (in my opinion) is in high horsepower applications where they are needed. Other than that, if I am going to put up with an automatic, I like TH700R4's. I can also rebuild them for a couple hundred bucks though.

Martin
 
That being said, I am not trying to dog on this swap, if that's what you want, go right ahead.

Martin
 
TH400's are too big. Too much parasitic loss. The only use for them (in my opinion) is in high horsepower applications where they are needed. Other than that, if I am going to put up with an automatic, I like TH700R4's. I can also rebuild them for a couple hundred bucks though.
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my take on this.....

I wouldn't give a 700r4 a second look..... seen too many of them fail..
rebuilt a few for family /friends...never was happy with the way they turned out....
I've had friends spend big bucks for high dollar / high performance upgraded 700's and they were trash in a matter of months...I just can't see spending 1500.00 plus on these transmissions...


Turbo 350's... good overall trans for mild wheeling / mild hp engines..
easy to rebuild... reliable/ decent strength... only down fall.. the 4 bolts at the adapter / tail shaft are known to strip/pull threads... studs/red locktite and back up nuts and washers help..

Turbo 400's....stupid strong....handled blown big block power in my blazer for a long time..weak point...thin casting at the output housing end of the trans case is prone to cracking ( I broke 3 cases there) cracks are not fatal to the working of the transmission,,,they just cause drooling leaks....

I run a T-400 and doubler set up in my buggy behind a BBC and I doubt that the trans even knows that there is "parasitic drag"....for my money...I'll stick with the 350's and 400's. :bow:
 
Yeah I haven't noticed any "parasitic drag" so far. I'm not sure how I would even measure that. I'm not going to dyno this old piece. Maybe it's just the fact that I now have a trans with new internals vs. my old worn out one, but the truck seems to take off better and rev out a lot better. If I give it light throttle, it shifts into second at about 12 mph and if I put it on the floor, it will rev out to about 40 in first. The 700 may have a lower first gear, but it would bang into second pretty hard way sooner than this 400 does. I don't think I would ever fool with another 700 if I had the choice. I think they probably do save gas when they're new/newly rebuilt in a vehicle with a stock engine, tires and axle gear ratio. Other than that, I don't see any need for me to mess with them.

I still don't care for automatics though. As good as this 400 seems to be, I still don't fully trust it. If I had a parts truck with all the stuff to put in an SM465, that's what I would have done. Oh well. I'm sure I'll be doing some more swapping in the future.
 
400s suck power. My camaro lost 75whp going to a 400 from a manual.
 
I think any more I'd take some power loss for reliability. I've owned a couple th400s and worked em hard and even overheated one to were it blew atf out the dipstick all over the engine. I topped it off and ran it for the rest of the year until I swapped in a sm.

Pretty sure they make lower first gear sets for the th400 too.

Of course the 4l80e is nice too....

I thought I read somewhere that the tall first gear is for starting out easy with a heavy load. No jarring, parts braking jolts. But this could be mythical internet hearsay
 
COCHEV said:
I thought I read somewhere that the tall first gear is for starting out easy with a heavy load. No jarring, parts braking jolts. But this could be mythical internet hearsay
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The TH400 was first used in cars. Their use in pickups was secondary.

Martin
 
Automatics can be fickle...I had a TH400 in my '69 GTO and I used to love doing burnouts,it had a non-posi 4.11 tear axle and could smoulder one rear tire for 300+ feet easy,and I often would floor it in second gear around a rotary and have the tire smouldering all the way around it--in the rain you could spin the wheels endlessly in all 3 gears.............................................One winter I parked it in my sisters yard on the lawn,and we got a 12+ " snowfall--I tried backing the car out of there and got it badly stuck--spent a good 45 minutes rocking it from first to reverse ,before it finally came out of the ruts it made!...next day,the tranny sounded like a siren when I started the car,like a P/S pump low on fluid...I noticed it didn't go right into gear,it now hesitated a few seconds and seemed to "slide" in,instead of the usual immediate firm shift...................................................................................................I took the car to a gas station where a friend worked,he let me use the lift,and I changed the fluid and filter in it--the pan was FULL of what looked like coffee grounds,probably clutch pack peices!..but after getting it back together,the noise went away,and the tranny once again went into gear immediately and would still spin the tires and bark second gear just as it always did...I drove it another 20K miles before I sold it,never had a problem with the tranny at all....despite all the punishment!.........................................................................................Other guys I knew with Buick Grand Sports would lunch a TH400 in them almost monthly,one guy decided he hated TH400's and bought a used TH350 and put that behind his 455,and never had any troubles with it.......................I owned a '72 K5 with a TH350 that would refuse to go forward first thing in the morning or after sitting several hours--once the engine warmed up a bit,it would suddlenly go in drive--then you could drive it 500 miles if you wanted and it worked fine,till the next day,when the process repeated...after nearly losing my job from being late a lot because of that,I decided to swap in a SM465 setup...looking back,I would not do that again,unless I had a better rear axle ratio than the 3.08's it had...it was pretty doggy, and too high geared....but at least I knew chances were good it was going to MOVE when I let the clutch out!......................................................................................................My 82 K2500 has a TH400 behind the 6.2...though it was supposedly "just rebuilt" before I got it,and maybe it was,its never had the proper vacuum going to the modulator valve,I had to run the line direct from the vacuum pump to the modulator and turn in the adjustment screw in order to get it to upshift correctly ,because a valve on the injector pump that regulates vacuum was fubared..it shifts "early" but it doesn't slip,if anything its a bit harsh when it upshifts..but despite me beating the crap out of it plowing for almost 10 years in many 2+ foor blizzards,its still hanging tough....the truck is no dragster with this tranny/engine combo,however!...I've driven another truck with a 6.2 with a SM465.and you definately can tell the difference the TH400 makes as far as robbing more power...
 
Whoa son. That was the longest post I've seen on here in a while. Are you sure Fordum didn't take over your computer remotely or steal your user name or something? Hahahaha.

Good stories though. I don't doubt that an auto trans robs power. Anyone can tell that. I've found it quite interesting to read everyone's opinion on this topic. I should have known there would be a lot of different schools of thought. Right now I can only go by my experience with these two trannies because they're the only automatics I've ever owned. And so far the 400 is anhilating the 700 in my old junk pile. Only time will tell if my opinion changes. It has been known to do that sometimes.
 
As good as the TH400 seemed to do at first, now I seem to be having a weird problem. The other day it started acting funny and I found out it was low on fluid, so I added some. A couple of weeks later it started doing weird stuff again and it was low on fluid again. I got up under the truck and couldn't find any evidence of the trans having leaked out anywhere. (The transfer case and engine are a different story). So I took the line I had made off of the vacuum modulator and transmission fluid puked out of the hole a little bit. Same thing at the other end where it goes into the intake manifold.

I know this sounds weird, but it looks like the vacuum modulator is letting transmission fluid escape out of the vacuum line and go into the engine. Also, I can tell that the exhaust pipes are blowing out some kind of fluid because there's some weird greasy spots all over the tailgate. What's going on here? This is a brand new adjustable vacuum modulator.
 
Your vacuum modulator is junk, the rubber diaphram has a hole in it and your engine is sucking tranny fluid into the intake and burning it, and your vacuum modulator is probably not modulating tranny fluid pressure correctly either. Get a new modulator, you must of bought a bad one unfortunately.

Hopefully the fluid didn't get low enough you damaged your clutches, low enough it was acting funny isn't good, hopefully you fixed the fluid level immedatialy and you can just swap the modulator with one bolt and be done in 2 minutes.
 
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