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Old October 22nd, 2009, 03:05 AM   #1
Disturban
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Default Transmission guys?

1988 Suburban th400/350cid...I just picked up a 454 and am rebuilding it. I plan on dropping in the motor in the spring. Mild built with heads and cam 450-500hp. Questions, will my stock th400 be strong enough? If not what mods should I be looking at? Keep in mind that my truck see's a lot of different uses such as wheelin, towing, pulling people out of ditches...it is a work horse!

One more question...does my transmission have a computer controlled lock up converter? I am planning on running a carb and doing away with the computer...so if it does have a computer controlled lock up converter can I just swap it out with a converter from an early model th400?
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Old October 22nd, 2009, 04:54 AM   #2
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as for the trans the newer 400s are not the same as older ones. you should check http://www.tciauto.com/Products/GM/g...amatic_400.asp

as for parts anything that fit the `86 trucks should be usable on yours. I tend to wonder about the fuel sender? as I can't remember if it used an intank pump or a piggy back set up like the diesels did?

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Old October 22nd, 2009, 05:50 AM   #3
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as for the trans the newer 400s are not the same as older ones. you should check http://www.tciauto.com/Products/GM/g...amatic_400.asp

as for parts anything that fit the `86 trucks should be usable on yours. I tend to wonder about the fuel sender? as I can't remember if it used an intank pump or a piggy back set up like the diesels did?
That does not tell me a whole lot...the main thing I need to know is if I have a lock up converter that is controlled by the computer? Other mods can be made later, my main goal would be to just get it going.
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Old October 22nd, 2009, 06:04 AM   #4
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A th400 does not have lock up. What is the history of the stock th400? If it has a lot of miles on it, It wouldn't hurt to have it gone through and beefed up a little bit.
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Old October 22nd, 2009, 06:09 AM   #5
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Ya what year is the TH400?? I'd get it rebuilt at the least, then tell who ever is rebuilding it what you plan on doing w/ it!
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Old October 25th, 2009, 09:43 PM   #6
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1988 Suburban th400/350cid...I just picked up a 454 and am rebuilding it. I plan on dropping in the motor in the spring. Mild built with heads and cam 450-500hp. Questions, will my stock th400 be strong enough? If not what mods should I be looking at? Keep in mind that my truck see's a lot of different uses such as wheelin, towing, pulling people out of ditches...it is a work horse!

One more question...does my transmission have a computer controlled lock up converter? I am planning on running a carb and doing away with the computer...so if it does have a computer controlled lock up converter can I just swap it out with a converter from an early model th400?
Your trubo 400 is what they used behind the 454s back in the day anyway, a 4L80E is an electronic th400 just like the 4L60E is the electronic version of the 700R4/4L60

It should bolt right up and be usuable as is, though i'd reccommend a shift kit for the 400, it hold up better bolted to the 454. It doesn't have a computer controlled lock-up converter
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Old October 26th, 2009, 07:53 AM   #7
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Your trubo 400 is what they used behind the 454s back in the day anyway, a 4L80E is an electronic th400 just like the 4L60E is the electronic version of the 700R4/4L60

It should bolt right up and be usuable as is, though i'd reccommend a shift kit for the 400, it hold up better bolted to the 454. It doesn't have a computer controlled lock-up converter
A 400 doesn't have a lock up converter period.
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Old October 26th, 2009, 08:20 AM   #8
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A 400 doesn't have a lock up converter period.
Thanks...thats what I needed to know, I am good to go!
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Old October 26th, 2009, 08:33 AM   #9
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one other thing to consider.... Is your truck currently a TBI motor? The kick down switch is actuated by the tps voltage and ecm on a TBI motor. That's easily fixed buy installing a switch from an earlier truck on the accelerator bracket.
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