Turbo 400 Build - Mega Carnage to Better than New.

[crazy4offroad]

Nice writeup, I cant wait to see what kind of magic and insider tips you have for the plain jane TH350 (since I have one in my basement begging for my attention).

 

[HotRodPC]

Nice writeup, I cant wait to see what kind of magic and insider tips you have for the plain jane TH350 (since I have one in my basement begging for my attention).

Not really alot needs done to a Turbo 350 either. I actually like Turbo 350's better than I do Turbo 400, although a 400 is going to handle more abuse and last longer than a 350. Same thing in a Turbo 350, go for the wedge dog bone sytle sprag cage. Then an upgraded aftermarket sprag gear, and updated aftermarket input shaft and those are the 2 weakest points in the Turbo 350 as far as I can recall. Sure there are more billet parts etc if you want to run 600hp or more, but for the basic mild mud truck those few upgrades will beef up a 350 nicely.

 

[HotRodPC]

OK Boys and Girls, Ladies and Gearheads, I am posting an update to the 400 Write up. This is not the same transmission as built above, but another Turbo 400 I am building for a bud. I have never run accross this problem before, so in case anyone else ever does, here is how I handeled it. This is the bolt that goes thru the valve body area of the transmission into the Center Support of the transmisison. The bolt head uses a 3/8 12pt socket. Not a hexed 6ft. The bolt also has a hole thru it to transfer fluid, so its a very rare hard to find proprietary bolt used only for Turbo 400 transmissions. This transmission had been sitting outside in the weather and rain for months maybe even up to 2 years. So bolts and parts are a bit rusty and corroded being the case is alluminum. The Center Support bolt, 3/8 12pt, rounded off. I tried everything, even tapping a hex socket over it to no avail. I decided I was gonna have to easy out it. The easy out was small in that fluid hole, I was afraid it was going to break, but the Vise Grips just let go anyway. It was so small the vise grips didn't get a good bite. So with nothing to lose, using extreme caustion to keep the drill bit straight and follow the same hole, I drilled the hole to at least double the size. A bigger easy out now fit in the hole. The Vise Grips bit into the easy out great. But still it didn't give up. So of course I had already sprayed some WD-40 into the hole. The WD-40 had done all it was gonna do now and was not puddled up at all. I decided to get out the torch and add some heat to it. I had the torch directly on the bolt for about a full minute. Then tapped the easy out into the bolt hole, put the vise grips back on the easy out and held good very strong pressure for about 20 seconds and boom, broke it loose. So if you ever get in that situation, that is the trick. Drill the hole to about or just over double size. Heat the bolt, and its heat will also transfer to the aluminum case. Then thread the easy out into the hole and hold good strong pressure with the vise grips until you feel the bolt give up. Then of course you will have to replace the bolt. Good Luck there. I happen to have a spare one here from my transmission core supply. Keep in mind, this is going to leave some shavings inside the case that you will need to make sure you get completely out of the case before you start your build. Very Important to get them all out. They are course shavings for the drill bit, and will hang a valve in the valve body in a half of a second and lead to trans failure. Here are pics of the bolt location, and a pic of the socket, new bolt and bad bolt.

 

[Manbearpig]

Spent $30 on trans fluid

Thats cheap for trans fluid

 

[HotRodPC]

Thats cheap for trans fluid

Yes, If I recall, the cost was $8.69 or $8.99 on sale at Walmart for the gallon jugs. Maybe $9.49. Not sure but it was cheaper by the gallon and I got 3 gallons. It was late at night so I had to go to 24hr SuperCenter and buy it, and I got their Super Tech brand in Dextron ll.

 

[Manbearpig]

The blue jugs?

I have a couple of those but have been reluctant to try the stuff out lolol

 

[HotRodPC]

Yep, The blue ones. I think its Super Tech Brand. Its not bad stuff at all. As long as it has the proper properties and ratings, then its good for transmissions. If it didn't meet that criteria, it would be illegal for them to label it as such. So I don't get as picky with T fluid as I do motor oil.

 

[Old77]

Somehow I'm just now seeing this thread! Nice write up

 

[HotRodPC]

Somehow I'm just now seeing this thread! Nice write up

See, you learn something new everyday on this site. You got today out of the way already. Thanks for the kudos. I hope to be having a Turbo 350 and a 700r4 build thread up soon too, like within this month. Never know how the holidays might affect it though, but certainly by the end of January. Those build threads really are time consuming, and they also slow down the build itself, trying to stop in between, wash the hands, grab the cam and take pics. But, the pay off is there. Occasionally, I find myself looking back over my pics if I think something is missing or I find an extra parts. LMAO, parts leftover after building a transmisison, is NOT a good thing. Rarely happens but on a T400 for example, earlier models have a thicker Center Support and do not have one of the bigger snap rings. The later ones have a thinner Center Support and use that big snap ring and its purpose is called Case Saver. Just one of the very few design changes along the way to make the trans better and avoid wearing out the case. So when I think, where is that snap ring, and can't find it, I can look at my tear down pics and realize, Oh this case didn't have it. Duhh and carry on.

 

[Old77]

I definitely do learn something new every day! The other day it was about Nomads (that were produced into the 70's) and that Pontiac had a version as well, then it was that Chevy had a full size van called a "Caravan", then it was..... the list just continues to grow!

 

[HotRodPC]

Well boys and girls. Just an update on where I'm at on my buds 400 rebuild. I finally got the thing apart. Every servo pin was seized in the case along with the servo pistons. The Vac modulator valve is seized in the case and no way to get it out since it can't be tapped or hammered thru like I did the servo pins. It hat to be vatter anyway, as I do all rebuilds. Thinking the vat may clean it up and loosen the vac mod valve, I took it to the machine shop. Machine shop calls says they ran it 3 times and its not coming clean. Went and picked up, sure enough bad shape. I could see all the funkyness and crusty junk in the valve body passages. Even if I was to get that **** out of there, its still going to be throughout the trans where its not exposed and can be seen. So as bad I hated to, I suggested to the bud to get another core after he just spent $100 on this one. Lucky for him, he had a T350 that had been recently rebuilt out of his pick up that this 400 is being built for. A guy had been bugging him to trade a T400 for his T350. The guy needed a T350 to swap out a T200 junker from an 82 Cutlass I beleive it was. So they swapped + my bud got $100 since his was recently rebuilt. Seems this new core he swapped for is going to be great. Its a 89 truck 400 out of a 3/4 ton. Nice fluid color, and very clean inside. Look at the differance of the one had been vatted 3 times, vs the one that has not even been vatterd yet. The new one should be a good build and finally I can get on with this project. Its been in limbo far to long crampping my style.

 

[HotRodPC]

BTW, I know I skipped around a few things on the original write up, so if anyone has any questions or needs pics of anything to do with the 400 build. Lemme know. I can get requested pics this time durning this build. I may get more pics anyway and include some of the details I didn't last time.

 

[HotRodPC]

I am likley going to be building another TH400 within the next month. Anyone have any special requests??? Should I do a thread on it or is this one good enough for everyone? I am hoping the next one isn't a rush job. Its already been disassembled and cleaned, but its going to be building parts from 2 differant TH400's to make one. Its pretty much going to be a stocker TH400 but with a Stage 1, RV/Heavy Duty shift kit in it. Its intenton will be for the 88 Burb project.

 

[davbell22602]

That one trany looks nasty.

 

[89Suburban]

I think it will be easier to follow if you keep the dissasembly and assembly threads separate boss.