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700R4 or TH400 - which is best?

J

jstevenj

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I finally found and bought the Blazer I've been looking for for the past several months. It's a stock 87 model with the factory 350 TBI. I plan on adding about 6" of lift and maybe a body lift. I have a set of 14b, d60 axles for it with 4.56 gears. I will be adding a 205 with a custom adapter for the tranny. I intend to stay with an automatic transmission. I need some advice on which tansmission I should use. I have the stock 700R4 that is in the vehicle (which seems to be in good condition) and I have a good used TH400. I'll be making the tcase adapter either way I go so that's not a factor. The engine is stock but has good power and I don't plan on building it. I plan on running 42" tires. So which way should I go, 700R4 or TH400? Give me some pros and cons please.

This will be a play truck, mud holes, trails and an ocasional trip in to town to show off how muddy it is or to get a milkshake on Friday night. It will not be a daily driver.

Thanks, Steven
 
With 42" tires the TH400 would last alot longer than a 700R4. But a 4L80E would be the best choice for a strong tranny yet keeping an overdrive. However 4.56 gears are going to make that OD useless. You would want to run 5.13 gears if you keep an OD with the 42's.

What is your plan with the blazer? Offroad only, daily driver or mixed?
 
Well with 4.56 gears and 42's you will burn up both trannies. The th400 burning up slower. You need at LEAST 5.13's for that big of a tire.IMHO. Do you ever drive on the highway? Bottom line if an over drive transmission would benifet you and you can control the temp in the transmission than I would keep the th700 and buid a badass one when that one eventually burns up. If you don't need OD than I would just swap in the th400 and be done with it.

I have a built th700 and I love it because I get better mileage on the highway, quiets my motor at 65mph, low first gear, and easy to adjust TV cable. If it wasn't a daily driver that saw a fair amount of freeway miles than I would have just put a th400 in because that would have been cheapest.
 
I would probley use the th400 for your use. Put a huge cooler on it, slap it in low-range and roll. /forums/images/graemlins/pimp1.gif
 
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Well with 4.56 gears and 42's you will burn up both trannies. The th400 burning up slower. You need at LEAST 5.13's for that big of a tire.IMHO.

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Yeah, 2200-2400 RPM cruise sure burns up those TH 400s quick. /forums/images/graemlins/rolleyes.gif If I recall correctly, your cruise RPM with 4.10s and 35s with overdrive is about 20% lower than that.

So, if what you say is true, your tranny is under 20% more strain than that TH 400 or so, considering your cruise RPM is 1800-2000 or so.

/forums/images/graemlins/rolleyes.gif /forums/images/graemlins/rolleyes.gif
 
I was going to ask this too, what is the strongest tranny between the TH400 and the 700R4? It will not see on road driving alot. It will have 44"'s with 5.13's of course. Used for mudbogging if no-one has seen my signature /forums/images/graemlins/grin.gif
 
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I was going to ask this too, what is the strongest tranny between the TH400 and the 700R4? It will not see on road driving alot. It will have 44"'s with 5.13's of course. Used for mudbogging if no-one has seen my signature /forums/images/graemlins/grin.gif

[/ QUOTE ] A stock th400 is stronger than a stock th700.
Aftermarket wise a th700 like mine or bowtie OD's is just as strong as a stock th400 basically. Modified th400's can take crazy HP, just ask mudjunkie82.

My question to you guys is why do you even consider a th700? They can be finicy trannies and require regular maintance and cool running temps. The only reason I would think a th700 would be needed if it is a daily driver and OD will be used a lot. If it won't see onroad use much( or higher speed traveling for that matter) than just run a fresh th400 with a shift kit and good cooler and forget about it. Don't waist time building a th700 that can handle big tires and offroad abuse because you can't use OD anyway.
 
My vote goes for the Turbo 400. When it comes to reliable automatic transmissions the T-400 has proven to be the best there is. The T-400 is controlled by valve body fluid only, and not a computer (at least the last T-400's I remember where).

One thing you need to take into consideration though is that your truck is a computer-controlled vehicle, and taking out the current transmission, with a speed sensor, is going to negatively affect the performance of your truck radically, unless you are ripping out the computer, and all its input devices on your truck. The computer on your truck needs the transmission speed sensor to help control everything from shifting, to ignition timing, and fuel mixture.

The manual 4-speed SM 465 is probably the most bulletproof there is, literally. If you shot at SM 465 at close range with a .458 magnum, you had better duck because it going to ricochet right back at you.
 
[quoteAftermarket wise a th700 like mine or bowtie OD's is just as strong as a stock th400 basically.

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That is quite possibly the most ridiculous bunch of crap I've ever heard in my entire life.

I don't care what you do inside a 700R4, it will never even approach the strength of a stock TH 400.

Not saying that a 700R4 cannot be built, but to compare it to a TH 400, built, not build, or worn out is absolutely ridiculous.

There is a reason that GM didn't put a 700R4 behind big blocks or in 1 ton trucks and it sure isn't because they could have designed enough strength into it to make it live.

If you look at the outside dimensions of a 4L80E it takes a much larger transmission in physical size to make an overdrive automatic that will live in a heavy duty application.
 
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My vote goes for the Turbo 400. When it comes to reliable automatic transmissions the T-400 has proven to be the best there is. The T-400 is controlled by valve body fluid only, and not a computer (at least the last T-400's I remember where).



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A th700 isn't computer controlled, just the converter lock up....the speed sensor is in the transfer case.
 
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A th700 isn't computer controlled, just the converter lock up....the speed sensor is in the transfer case

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Thanks! /forums/images/graemlins/thumb.gif

I Got out of being a mechanic in the late 80's, and got into a different occupation, when a lot of the computer controlled stuff for trucks started coming out. That is why I am not really up on the transmissions like the 700 R4, 4L60E, or the 4L80E

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That is quite possibly the most ridiculous bunch of crap I've ever heard in my entire life

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Don't sugar coat it, tell us how you really feel.
 
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My vote goes for the Turbo 400. When it comes to reliable automatic transmissions the T-400 has proven to be the best there is. The T-400 is controlled by valve body fluid only, and not a computer (at least the last T-400's I remember where).



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A th700 isn't computer controlled, just the converter lock up....the speed sensor is in the transfer case.

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My 700R4's lockup was controlled by a vacuum switch.
 
Whole lotta opinion on here, this comes down to preference the 700 has a lower first gear ratio and lock up feature it also can be built to take anything. The 400 has a reputation for being strong....
You can break anything at anytime, for my money and not the trail only trucks the 700 is awesome. Which is to say my preference would be that. There is no doubt that you can build the 400 to take alot of abuse. Just keep in mind that if you decide to use either one or even the odd ball comment tranny (465) they can all be broken....
 
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That is quite possibly the most ridiculous bunch of crap I've ever heard in my entire life

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Ahhh, I bet Tim is running his babbling mouth with useless garbage pouring out of it like always. He probably is spewing out crap about a th700 like he does in every tranny post. /forums/images/graemlins/histerical.gif

Thank god I finally put him on my ignore list, life is so much quieter and not crouded with so much useless BS anymore. I highly recommend it as a great stress reliever. /forums/images/graemlins/thumb.gif /forums/images/graemlins/rotfl.gif
 
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Whole lotta opinion on here, this comes down to preference the 700 has a lower first gear ratio and lock up feature it also can be built to take anything. The 400 has a reputation for being strong....
You can break anything at anytime, for my money and not the trail only trucks the 700 is awesome. Which is to say my preference would be that. There is no doubt that you can build the 400 to take alot of abuse. Just keep in mind that if you decide to use either one or even the odd ball comment tranny (465) they can all be broken....

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Yep, Th700's can be built up offly strong, stronger than a th350 and as strong as a stock th400 IMHO. Get an 82'-86' th700 though and you might as well head to the tranny shop because it will blow before you get there. It took GM a while to get them together right to last for a while. They still can't handle much power stock though and generate a lot of heat which is the cause of a lot of their failure due to poor cooling. Today there are a lot of aftermarket upgrades for them that take them to a new level vs. the older ones. There are a few members here that are running very large tires, good HP, and seem to be lasting fine. I've tortured my built th700 behind my torquey 406 and 35" boggers with no problems and it shifts better now than it did the day it rolled out of the tranny shop.

I still think that if the rig isn't going to see highway useage than you might as well go with th400 to save some money. The thing I don't like about 465's is that they are tiring shifting all the time in traffic. Offroad you have to know the rig well to know which gear you should be in for the on coming obstacle. I always liked not having to think about what gear I'm in when I was coming up to a big mud hole or hill... /forums/images/graemlins/tongue.gif
 
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A th700 isn't computer controlled, just the converter lock up....the speed sensor is in the transfer case

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Thanks! /forums/images/graemlins/thumb.gif
I Got out of being a mechanic in the late 80's, and got into a different occupation, when a lot of the computer controlled stuff for trucks started coming out. That is why I am not really up on the transmissions like the 700 R4, 4L60E, or the 4L80E

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No prob. /forums/images/graemlins/grin.gif Far as I know a 4L60 is basically the same as a th700 just that is completely computer controlled where the th700 isn't. I've always wondered how the computer controls the shifts, it is cool that you can just "plug" in a programmer and get a firmer shift. /forums/images/graemlins/ooo.gif
 
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http://dictionary.reference.com/search?q=offly

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Offroad you have to know the rig well to know which gear you should be in for the on coming obstacle

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Shouldn't you know your rig well anyway if you're wheeling it?

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Obviuosly but that doesn't mean you're used to every obstacle either. Say it's a mud hole and you choose a gear estimating how deep it is...it's deeper than you thought and it bogs you down and you're stuck. Thats all I was thinking. I have seen it happen but never done it because I have always had autos. /forums/images/graemlins/dunno.gif
 
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