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Friend's truck: conversion from turbo 400/NP208 too a 700r4/NP205

allenhillview

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Jonesborough, TN.
Hey akonitony, can one builder (any good builder) do a th400 better than it is in stock form to tow my trailers without breakdown if not abused? I want to go out on a trip without worry. I'm not going to get there fast but I like mountain roads always have trailer with me. 5000lbs.trailer,6.2engine, 4:56gears. Should I leave it alone till it breaks?
 

Iceman3005

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Holt, MI
every 205 had the ability for PTO
Yup all NP205's had PTO ability. As for an update, project was finished in the late summer, the owner of the truck loves his lower first gear and the overdrive, "70 is a lot quitter" he told me a few weeks after I completed it. He also likes the NP205 for its strength and the PTO option. He hasn't installed is PTO yet, said he is waiting for warmer weather. @akonitony: yes the 700r4's are not beefy but with a few upgrades they can handle a decent amount of HP going through, besides how many guys are running more than 500 HP in there daily drivers.......not many. As far as the 700r4(4L60E) they are Identical except for the "E" means the computer controls shifts. The 4L65E internals (hard parts, clutches, shafts etc.) can be put into a 700r4, this combo allows for a very beefy trans with out having to use the computer to control it, the valve body from the 700r4 it used to control it. Also what I like about the 700r4's is there are 100's of thousands of these everywhere so there cheap, most can be bought for $100 to $200, and for another $400-600 it can handle 300-400HP.
 

Iceman3005

Active member
933
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Location
Holt, MI
Hey akonitony, can one builder (any good builder) do a th400 better than it is in stock form to tow my trailers without breakdown if not abused? I want to go out on a trip without worry. I'm not going to get there fast but I like mountain roads always have trailer with me. 5000lbs.trailer,6.2engine, 4:56gears. Should I leave it alone till it breaks?
I think the turbo 400's were rated for 15,000 GCVW, and 350 HP, so the 6.2 and the trailer your towing shouldn't break the trans, I think you will be fine. My dad had a 454 with the turbo 400 and we pulled over 20,000 GCVW (truck, trailer and load) all the time with out any issues.
 
Hey akonitony, can one builder (any good builder) do a th400 better than it is in stock form to tow my trailers without breakdown if not abused? I want to go out on a trip without worry. I'm not going to get there fast but I like mountain roads always have trailer with me. 5000lbs.trailer,6.2engine, 4:56gears. Should I leave it alone till it breaks?
In my experience, it seems TH400s usually go out gradually, and it is usually burned up steels (each clutch pack has frictions and steels, and the frictions are the clutch material with the steels acting as pressure plates). TH400s are notorious for being hard on their steels. I always replace the steels with new ones no matter how wonderful the old ones look. The two main upgrades I recommend on these units are a dual-direct-feed upgrade, which modifies the center support in case the trans is subjected to RPMs in excess of 5500 and a pressure leak may develop without this mod that actually bleeds direct oil to the reverse piston, and will cause a serious bind, which with a diesel, probably will never happen, and the other mod is installing a shift kit that will correct early, soft shifts, which is another problem with these guys. Gil Younger makes a good one under the tradename Transgo. His kits are as good or better than the bigger names, and they are very reasonably priced. One other mod to make, especially for towing, is what I call the TH350 pump bearing mod. You take the torrington bearing that goes right behind the pump in a TH350, knock the rear case bushing on the TH400 you wish to build in just a little so the inside edge of it gives you a lip, then set that pump bearing in where the rear thrust washer used to go. Under heavy loads, the helical-cut planetary gears in TH400s will force the geartrain backwards and create pressure on that thrust washer, and eventually cause oil starvation. GM tried to fix this with straight cut gears back in the '60s, and a good set of those will set you back 500 clams easily, if you can find a set that is. The torrington bearing will also fix this problem since it is impossible to oil starve this type of bearing no matter what amount of pressure is against it. It also lowers friction quite a bit. This is very noticeable when you place the output shaft / ringgear assembly on top of it and turn it when comparing it to a unit built with the standard thrust washer back there. One other way to alleviate the condition is to size the backing plate for the thrust washer down a few sizes, as it is selective, and this will give extra endplay to the output shaft and make it harder to oil starve that washer. I'm a big believer in having the correct endplay set up, so I highly recommend the TH350 pump bearing thingy back there, and fix it and forget it.
 
I'm glad to see the 700 used in this thread was a K-model. That case is worth it's weight in gold, well, maybe not gold, but definately more than aluminum - lets say copper. They are getting harder to find, and they can easily be identified by the big K on the bell housing, or if the unit is still in the vehicle, and all you can see is the bottom, the torque converter cover will be cast aluminum rather than stamped steel, and the bolts will have 13mm heads holding the cover on rather than 10mm.
 

allenhillview

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Jonesborough, TN.
Wow what a ton of info, but you explained it well. All I can do is print this and wait, my truck has 28,000 on it no issues at this time . Who knows it might make it a while. I'm sure the heat will take a toll and I expected it so when I got the truck I installed a mechanical temp. gauge, akonitony I just Didn't put that in pan I put it inline with all new stainless and built manifolds for it and oil,AN stuff etc. ,so I'm watching close. Also may add cooler but I've look at them a year the one I want is five hundred, hand made, aluminum,all one piece design,AN adaptable, I'd have to look it up its been awhile, but i think fluidyne he called did a good job explaining his product. So Thank You a lot for this. I keep these reads when they stick out to me as this one has.
 
... Also may add cooler but I've look at them a year the one I want is five hundred, hand made, aluminum,all one piece design,AN adaptable, I'd have to look it up its been awhile, but i think fluidyne he called did a good job explaining his product. So Thank You a lot for this. I keep these reads when they stick out to me as this one has.
While heat is the biggest enemy of a transmission, I think you might be going a little overboard with your $500 cooler. The main thing you want in an auxiliary cooler is for it to come in line after the radiator cooler has performed it's task as a liquid-medium cooler, you want the aux cooler to have enough GVWR under it's belt, and the tubing in it should have finning inside it to "stir" the trans fluid as it passes through. Hayden makes an excellent cooler, and you can probably find one for right around $100 or less.
Also, if and when you do a rebuild, kevlar is a great material for the bands in that unit, and don't let the builder talk you into red or blue fiction disks. They are pricey, they are only needed in extreme RPM/HP applications, and they will not break in properly if those high-RPM conditions are not met, but will tend to glaze enstead, and burn up the steels faster. Some builders prefer to build their transmissions dry, which means they don't soak the friction disks before building each clutch pack, but rely on the fact one will start the vehicle and probably let it idle for a few minutes before putting it in gear, and during those minutes, the frictions will get soaked with fluid as the pump pumps oil to them. Problem with this is nobody has put a little camara inside a clutch pack to make sure this indeed happens, and if there is even a small spot of dry friction material somewhere, when that clutch pack is engaged, that little spot will stay dry and glaze over, thereby preventing fluid from ever penetrating the material in that spot. Building the trans wet, that is by soaking the frictions in a bucket of transmission fluid for at least 15 minutes before placing them in the clutch pack, is a bit messier, but it is the only way to go. So ask your builder if he builds them dry or wet, and you'll know if you need to go with him or find somebody who doesn't mind getting their hands a little oily.
 
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allenhillview

New member
272
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Location
Jonesborough, TN.
Yes I knew about the turbulators in a cooler and will you advise me on a cooler which has all my needs? I'd like to get one with NPT's in the outlet, inlet , I don't feel the fan deal is all that if don't remote locate it,which I don't want to do ,fear of hay and grass clogging it up in the field,not much if any week-end trails but always off road in pasture land with hay,cattle,fertilizer,feed..etc. That given if I put it out front I'm OK. I also knew of the radiator cooler first then aux. sometimes fluid could be to cool for correct flow. So, go aluminum? Hayden is your pick? I'm never over 23,000GVWR! Get at least that size(cooler) but not over? Will I lose pressure? I've been told not,since pump and what it does never reaches its capacity? Do you like plates or tubes? That Fluidyne is all one piece but pricey 380.00( no fan) Tell me if you will of that builder you mentioned? My brother spent a lot on Dodge with Mag Tech it does good but I don't need what he got he is running a lot HP for road trips with horses. I'll never exceed 200 if I tried. Fuel(mpg) is important then you also get into new truck price with some of those builds I just want to go and go,no tranny issues from heat with trailers. Gone on long enough so thanks in advance.
 

Iceman3005

Active member
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Location
Holt, MI
Not sure yet. Going back to the drawing board to make them a different way. I let you know in a couple of days.

Sent from my SM-G928P using Tapatalk
 
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