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1984 c10 5.3 turbo.

Old 12-27-2018, 01:56 PM
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Default 1984 c10 5.3 turbo.

Hi folks, kind of a new guy here but been lurking on LS1tech for a long time. I recently started a swap build on a 1984 c10. Among smaller issues like getting the engine brackets from a SBC because the i6 ones don't work, I'm having a hard time figuring out what to do about the transmission. I'm in Alaska and to say the least our junkyards suck. 0 luck finding any 2wd th400's or 4l80's. 4x4 transmissions everywhere though. So I have the th350 I pulled from the truck, it has 50k miles on it. I have a 5.3l with a 78/75 and shooting for 600-700hp crank.

Penciling it out, the transmission guy can do a build on a th350 or th400 for 900 which includes a shift kit clutches, etc... but if i want any upgraded sprags or shafts that's extra and on me to find and buy. I can get a used, th400 for about $500 but its 4x4 set up. So thats another $300 in parts for just a housing and tail shaft to convert it.
Th350(own it $0)+rebuild(~$1200-$1300)
th400($500)+tailhousing($300)+rebuild($1200-$1300)= ~$2300 probably

And that brings me to he real debate. Being where I'm at with limited access to used parts and limited access to builders that know how to build for this stuff. Do I just order a transmission through the mail? Five different outfits I looked out online have transmissions with converters for about $2000 shipped to me. But that's crazy risky to me buying something like that through the mail. This site has a sponsor i saw that didn't seems bad on prices and seemed to put out parts that made people happy. Some outfits had terrible reviews of course. If something happens to it I'm not sticking it back on a pallet.

So is it worth it trying to make the th350 work? I see them holding 600hp when done right. But its usually not a boosted application and usually not on a c10 long bed.

Last edited by LetsTurboSomething; 01-01-2019 at 04:15 PM.
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Old 12-27-2018, 02:13 PM
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i usually try not to push th350's past 350 wheel without upgraded internals.

you can probably make one live at 500 for a time

but you'll get bored of 500 and turn the boost up to 700 inside a week

you're money ahead to put a 400 or 80e in now. you can buy the output shaft and tail housing used on ebay for <200
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Old 12-27-2018, 06:03 PM
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you will want the 400 or 4l80 , 350s are great transmissions but require lots of expensive upgrades for big power , and you are talking huge power , an 400 or 4l80 can take that with minimal upgrades , ie , good converter and shift kit .
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Old 12-27-2018, 09:25 PM
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Got a lead on a BOP th400 with long tailshaft I think. Going out early in the morning to get it. $50 adapter plate seems like a better deal than a tailhousing/shaft swap.
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Old 12-28-2018, 09:37 AM
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4L80 for the win. Why not get better milage. You may think you don't care about it now, but it WILL be a asset to the build.
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Old 12-28-2018, 09:57 AM
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Originally Posted by Jimbo1367 View Post
4L80 for the win. Why not get better milage. You may think you don't care about it now, but it WILL be a asset to the build.

Like Jimbo says...this option is a win-win...
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Old 12-28-2018, 04:59 PM
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Originally Posted by CattleAc View Post
Like Jimbo says...this option is a win-win...
I totally agree, and would pull the trigger if the budget was set with that transmission in mind when I started. And I'll probably get a 4l80e as well and install it, it's just not going to be the first thing in there at this point. My issue is the cost to buy it vs the cost to own it/fix it. The th400 this morning was $300 and the guy threw in a set of engine tower brackets i needed, a good high stall converter and the yolk for it i needed. Nice old guy who raced cars for 30 years....pretty much where all the parts I need in this state are located are in the parts barns of these types of guys here. So meeting him was a blessing today.

There are 2 guys Ive talked to who do transmissions who even entertained the idea of working on a transmission for this kind of thing. Out of 7 places I called, 5 flat out didn't want my business. The two entertaining me didn't seem overly confident about it and neither had ever done a transmission for over 500hp, when i mentioned drilling a couple places for more fluid and lubrication they had never done it. Just shift kits and extra friction rings and stuff. No one does this stuff here, there is no real market for performance stuff unless its going in a diesel truck or maybe an import like a Subaru or jetta.I think I've only ever seen one single gas v8 turbo here ever.

The cost to do a stock rebuild on a 4l80e was over $2000. The cost to swap in just a 2wd tailhousing and shaft was $600 in just labor, shipping a 2wd one up would run about $500 in shipping charges alone.. I feel confident opening up a th400 my self, but not a 4l80. Ive just never done it. Cost to rebuild the th400 by one of those guys with a new sprag and everything was $1200. And from the looks of it, its no more complicated than rebuilding it like stock.

I'll end up building a second truck in the next year or so, so even if i swap the transmission out later having the th400 around isn't a bad thing since its become the largest headache of this so far. This just seems like the way to go for now. The 4l80 doesn't pencil out well for the budget, it basically costs more than the rest of the build.

I still have to pop the engine apart and regap the rings, change the cam, change the valve springs.
Rework the wiring harness
Figure out the lowering stuff, front end is just spindles and springs. The rear I'm debating on. There is a C4 complete rear end for sale, a few explorer 8.8's around and I keep staring at complete independent rear ends from Mustang SVT's, '13+ GT's and v8 early '90's Thunderbirds with the 8.8 diff. They look too easy to just weld in.
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Old 01-09-2019, 12:09 PM
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Got the transmission rebuild stuff in the mail yesterday. Going to pull this thing apart today, first automatic transmission I've ever done myself but I read and entire US Army SoP like 5 times over for the overhaul and the ATSG. Looks easy enough.

Does anyone have any recommendations for anyone on here that can help me with some remote tuning? I have a little experience with someone else's HPtuners and I finally have my own in the mail on its way here. I can fine tune once i get something in that can get it running but I'm leaning towards paying someone to help me get in a better starting position just so I'm not using up a whole month on basic **** like pruning out unnecessary systems. I've tuned on efi bikes and snowmobiles but not a GM vehicle or anything. I feel safer paying someone to start off.

Heh, 4" exhaust pipe stuck into the 4" notch I took out of the rad support and just ran the 3" piping through it. Used 2 poly bushing from an old ATV shock and sandwiched them between the cooler and the rad support and tightened till they squished. You can see that sweet bend i put in my perfect radiator when i dropped in on the floor from neck height....Need to pressure test it and make sure i didn't ruin it still.

$9 vice grips and 10cents in washers...worked impressively well by the time I made 2-3 beads, seemed to be the LS1tech go-to for at home bead rolling when i searched.

Last edited by LetsTurboSomething; 01-09-2019 at 12:24 PM.
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