TH400 Common Problems & MISTAKES!!!

[@corymollak2093]

Brother, as far as I'm concerned you've already redeemed yourself, as everyone in this field makes at least one or two major mistakes that they'll never forget. By taking the time and patience to sit down and make a video pointing out exactly what you did wrong...think of all of the Transmissions that you will have save. The lesson here is....ATTENTION TO DETAIL! It is essential to any technical troubleshoot or general build Thanks for the video and the heads up!

[@bigblocklawyer]

I have my dad's '65 Impala SS 396 with a TH400 he bought new in St. Louis. He traded his '62 409 Impala SS on it. He found out the then new TH400 was going to be in Chevys since they had been in BOP in 64. He ordered the '65 in Nov of '64 and took delivery June '65. The salesman at Weber Chevrolet called him every week to tell him it was still a good order, they were waiting on transmissions. So 7 months later he finally got the car. No wonder...first year engine, transmission and first Holley for Chevy. I was born in '70, and I remember he had some issues when I was old enough to know, one of which was the 400 slipping at times and shifting slowly between gears. He had a guy go through it and he swore he only pressure washed the case. I'm currently restoring the car and the guy that rebuilt it a few years ago said it was in amazing condition for 188,000 miles, and he did a very mild upgrade with a basic shift kit and what he said were premium parts. It's a 100% stock rebuild so it should last my lifetime. My rebuilder said there was an issue on the first year 400s that allowed corrosion to build up on some part that affected shifting and GM improved it on '66s. I don't know about that, but I've had countless 400s rebuilt for numerous muscle car restorations I've done over 40 years and they've always been amazing. I love these channels because I used to talk to my dad about stuff like this all the time. Wish I could talk to him 5 more minutes.

[@mountainsgarage]

Great story! Sorry about your Dad, lost mine a year and a half ago.

[@bigblocklawyer]

@@mountainsgarage Yeah. Sorry, too. I'm 51. All my heroes are gone.

[@siggyretburns7523]

Someday, bro.. someday

[@thomasdavison8996]

Love your honesty in this video, because like you said, it could help someone else. That is why I like your channel. Thank you!

[@455wagon]

I love that you give the bad with the good. We all mistakes....its how you handle them that makes us apart. Well done.

[@siggyretburns7523]

Its the same with hate. I know, it sounds wrong. But hate is an equal and opposite emotion like love, and is necessary. The value of your love is directly attributed to your hate. If you hate nothing, you either love everything or have no feelings at all for everything. And if you love everything, its potency declines. A man that loves all women means little to a woman that wants his all. Its natural to hate. But just like love, its how you handle it that describes your character. Balance. I just thought I'd throw that in. 😁✌️

[@BigFun4Life]

Thank you for sharing all your knowledge...Much appreciated..

[@novanut1964]

good video, very informative. i just identified a free transmission as a th400 started searching, your video was the first i watched and was glad i did.

[@skywaves5175]

Sorry to hear this. Very good video. Thanks Shawn.

[@jeepgodfabrication9970]

Thanks for sharing the tips. If you ever need a case or tail housing I have plenty. Everything I do is 4x4 and I’ve been trying to only use the case with the extra beef around the rear bolt holes. Usually I have double transfer cases hanging off the back

[@mountainsgarage]

Great to know, Thanks!

[@jasona6222]

A true master of his craft. I watched a few of your videos on the th400…not sure why, dont even own one. Thanks for sharing your knowledge.

[@nickthemechinick7279]

Awesome video thank you

[@bobbyemick4251]

Thank you for the videos

[@BigMikesGarage]

Sorry about your misfortune, but I sure appreciate you sharing your hard earned knowledge with the rest of us.

[@ShawnWasBorn2Ride]

Also appreciate your knowledge. Thanks for posting this. Sucks about the transmission housing tho :/

[@stuartbuckley8720]

Thank you for sharing your misfortune with us. Better days are ahead. Those cases are getting scarce.

[@mountainsgarage]

For sure, Thanks for watching!

[@brwpe7733]

Atleast you had another case to put the internal “pahts” in, now go eat some lobstah to celebrate that you finish that 8 bolt case. I know you won’t believe this but us hillbillies down south mess up now and then too. Thanks for being humble enough to help others with your mistakes!!!! Looks like you try and do qualify work and that’s much appreciated.

[@MrMk1098]

😂

[@hughmungus8784]

Thanks for this video

[@NATIVEWARS]

smart info here people and thanks for the video

[@alchampion340]

Thanks for showing your mistake. I’m. Gathering parts to build a 400 . I’m going to our studies in the two holes at the bottom of my pump, I’m going to shorten them so not to bottom in the seal housing. I’ll put two at the rear also just to ease filter change under the vehicle. Once again thanks for your Videos. 👍

[@mountainsgarage]

Thanks for watching, glad to help if I can!

[@joemessina2293]

Tig Weld it and grind it down then emery it so its nice and smooth and you will never know you broke it

[@daveyelmer3222]

I knew a master carpenter who was a marvel to watch in action. Years later, I heard he cut off a finger with his saw...... Point being, no matter how skilled you are, if your take it all for granted and lose your concentration for a second, something bad can happen...

[@mountainsgarage]

So true! I never stop learning!

[@richardsmith-qy6vl]

I love your videos you have so much knowledge to share I just tore up a perfectly good turbo 400 my friend built for me my big block 439 in my 88 monte carlo had a turbo 400 with a reverse pattern valve body now my engine only makes a lil over 650 hp 605 torque at 6200 rpm well I left real hard and brought it up to 6200 and shifted 2nd I seen a huge puff of white smoke then where 2nd was became another nutarul other then dyno pulls on this engine I only had about 20 miles on the combo. So I will be pulling it out to put my spare 2 speed 400 in which came out of my buddy's 496 blown 69 chevelle and hope it holds up and I hope when my friend takes the blown trans apart that the case is reusable I'm willing to be hè didn't put the case saver in ìt. Just so I'll know how much vacuum does it take for a non manual valve body turbo 400 to shift under normal driving conditions?

[@murkymurph8355]

Where do you source your beautiful hardware for tailhousing, pan, modular cover? Love how your work is functional and looks great! Thank you!

[@mountainsgarage]

I buy bags of flange bolts from either eBay or amazon lately, don’t have to leave the property that way!

[@timferguson1526]

Thanks!

[@krazobuildz7567]

Hey there I’ve been looking for a video on what the difference between the lower planetary assembly is there’s like 3 different types I’m aware of

[@charlesarata3801]

builder to builder we all do it i like your attitude i wish i knew you

[@mountainsgarage]

Thanks! Now we do!

[@cfmechanic]

Had th400 rebuilt and now it slips in reverse and first. I had them replace pistons with machined ones to fit 6 clutch stack also had them install close ratio planets. Car moves in reverse but barely however in manual low it is like a 2nd neutral. In drive car drives normal except for the shifts being rather soft. Any tips or ideas where they f..d up

[@1esaus]

Hi! I had an issue with my st400 on my buick wildcat 1964. I was driving down a long hill on low and when i shiftet to drive it suddenly did a hard jump and the engine died. I came to a stop in the intersection and put it in park and started the car. Then the car wouldn't shift at all. I wasnt able to get out of park. I went and felt under the car and noticed the gear selector mechanism had jumped out of the sprocket and put it back in. I was able to drive the car again and it shifts as normal. I do notice that it is hard to get it into neutral after that and somewhat before the incident. I also noticed yesterday that the manual lever plate has some slop to it and that it goes slightly in and out of the hole. Im guessing the pin inside the gearbox might have broken or come loose. Im able to drive it normally now however.

[@jasonchristian6560]

I have an 86 k5 blazer. I bought it with a bad 700r4. I put a turbo 400 in it had to replace the governor after that everything was fine until the other day. I went out started the truck let it run for about 20 minutes. Got in it put it in drive , nothing reverse, nothing. No forward or reverse at all. I shut it off let it sit after 2 hours started it and it tried to move so i changed the filter put it back together and it worked for about 2 days then lost all forward but good reverse any thoughts?

[@richardcordova8562]

I have a 1990 gmc sierra c1500 5.0 305ci with the 3l80 and have reverse but no forward gears and in reverse feels like e break is on when in drive gears moves as long as I don't give it throttle as soon as I do it kicks out of gear any advice

[@anthonyiannone7618]

Live and learn ,just use a power screw driver with torque settings next time instead of an impact

[@mountainsgarage]

Good idea!

[@turboryan]

I have TIG welded motorcycle cases on sealing surfaces hundreds of times that worked great. that case can be fixed for sure.

[@mountainsgarage]

I am sure it’s possible, but I couldn’t sell it and I wouldn’t run it, so to me its just a reminder to pay attention!

[@turboryan]

@@mountainsgarage well that's good to be particular. I have just repaired so much stuff like that it's almost sad that I didn't dedicate my life to something more important in that amount of time. ha

[@turboryan]

@@mountainsgarage If you don't mind I had a question on the th400 silencer ring. I see a lot of people don't use them but I read somewhere they help keep oil around the planets? I also read they where in the 4l80e the first two years but they went away. does it hurt to leave them in? I appreciate the videos!

[@mountainsgarage]

@@turboryan No doesn’t hurt. I only find them installed half the time. GM called it a silencer ring, don’t believe it has a oiling duty or it would always be there. You seldom find them in trucks, just cars where noise could be a complaint,

[@turboryan]

@@mountainsgarage I am curious how it makes them quieter... I could see if it held a bunch of oil that would help with sound... idk. I saw a video with the precision transmission guy talking about it, made me wonder. my straight planets in 400 are not too loud at all so it must work. I lost a seal ring in my trans and started pulling it apart and noticed the some of the parts I bought and gave my tranny guy are not inside. really grinds my gears so to speak. so I decided I need to do them myself. your videos are some of the best I have seen on this stuff. thanks for making them.

[@hackjobgarage9289]

Hey sir, I am trying to flush my TH400 fluid and I have the cooler lines disconnected and replaced my filter and O-ring. refilled the pan and ran it, at first fluid came out very slowly but now it has completely stopped. i noticed that it would suck fluid from the cooler return line but not from the pan. I have dropped the pan repeatedly to make sure the filter and pickup tube are sealed correctly. Am I going to have to tear it down and rebuild the pump maybe? Any advice or suggestions would be greatly appreciated.

[@bigbelconut]

Bummer about the case, can't uou weld it ans machine it. I have bored bores on a Bridgeport that big, take tiny cuts. Do you sell sfi 400 bellhousing? If so what do you charge? Thank you. Rob.

[@robertweitlauf4653]

can you drill and tap the shift shaft for a stud or bolt. and you can weld the case and hand file it or bore it on your mill.

[@mountainsgarage]

Maybe on the shaft. I couldn’t sell the case, and wouldn’t run it myself. So its junk at this point :(

[@robertweitlauf4653]

@@mountainsgarage i understand, my dad use to ask me if i would not run it on my junk dont run it on someone else's. your one of the good guys.

[@truckladders4104]

Great video If someone used the wrong pan bolts Could they not break the. Case. Even worse they might not notice until the trans started to haemorrhage out of the pump Good point on correct fastener s Thanks for the great work

[@mountainsgarage]

Yes, I have seen the results of using bolts that are too long. Thanks for watching!

[@chrisbeach992]

Anyone know what causes reverse issues on TH400 on 69 Chevelle. Car shifts fine while driving, but trying to back into garage and it feels like a parking brake is on. Have to literally floor it in reverse to get it to move.

[@ericshaffer7088]

Can't that case be welded. Tig or heliarc?

[@siggyretburns7523]

I think about all the VW transaxle cases we torched at Glamis. Magnesium is sure fun to burn though. When it gets going, it ain't going out until it all burns. One night we burned about 5 or 6 of them. Apparently, moths think they're neato too. Cuz the next morning, there were millions of dead moths in about a 50 foot radius. There was a bunch flying into us the night before, but we didnt know there was that many.

[@mountainsgarage]

Interesting!

[@siggyretburns7523]

@@mountainsgarage Well, the thing was, we were the only ones out there and I dont think there was a moon that night. So any kind of light would attract them for miles. And magnesium is pretty bright. There was another incident when my g/f and I lived in Anahiem. We had a BBQ with my neighbor. I guess we drank too much beer. So anyways, after the BBQ, he started asking questions about a transaxle I had laying around in the back yard. I told him about magnesium and he looked like he was doubting my word. So I decided to break off a chunk and burn it in the BBQ pit while the coals were still hot. I worked at busting that thing up for almost an hour and didnt even put a crack in it. But by this time I was determined to show him. So I said "F*** it" and threw the whole thing on. I told to go get some sunglasses cuz its gonna get bright around here in a few minutes. He didnt. But it didnt matter at that point because the police, helicopter, and fire dept showed up. The whole neighborhood was out in the alley looking over the fence. The cops told me to put it out. I said no. Then the battalion chief showed up and told me to put it out. Again I said no, but with an explanation. I told it was magnesium, I couldnt put it out if I wanted to and it would be stupid to try. He says "stand back, Ill do it". I told him again, Its magnesium. It'll explode if you put water on it. He said dont tell him how to do his job. I could see one of the other firewoman was trying to tell him too. I said fine. Let me get my dog outta the way I didnt think he'd really do it. I told him, look, it's almost burned out already. Just let it burn out. Right about then he opened up the hose on it and WOW. It blew a big assed mushroom cloud up in the sky. Hot coal went flying everywhere. I got pissed and yelled "What a dumbshit!!! Then he turned the hose on my g/f and I. The cops were standing there not knowing what to do. My g/f really lost it and was reaching her arm over the fence yelling and pointing her finger at him. He deliberately stuck his face into her finger. Then the cops jumped on her and arrested her for assaul and battery on a fireman. She has a nice rack, so they didnt miss the opportunity of ripping her shirt open. So the fire went out after the explosion. There wasn't anything left to burn. She went to jail, but was released on OR. She filed a lawsuit against the APD and the fire dept. We broke up a few weeks after that but we were cool about it and I said I would still testify for her. She had an $80k lawsuit for back injury, ripping her blouse open. She had plenty of witnesses. Everyone showed up for court...except her. Before the cops left my place, they asked me how I knew it was going to explode. I told him its something I thought everyone learnd in high school. Light a magnesium strip and stick it in a beaker of water and it stays lit under water, but kinda violently. Heres something you probably didnt know. Coffee Mate, the powdered stuff, it has a lot of magnesium in it. Take a pinch of it and sprinkle on an opened flame.

[@mountainsgarage]

@@siggyretburns7523 You would be a hoot to listen to around the campfire!

[@siggyretburns7523]

@@mountainsgarage If I didnt get us all blowed up.

[@MrLangleylad]

A broken case sucks almost as much as when people leave “labels” on new tires ! Come on Shawn ! lol

[@mountainsgarage]

If it had broken under some glorious acceleration then OK, but chasing threads :(

[@MrLangleylad]

@@mountainsgarage that is sad . I once fried at starter while putting on a timing tape on a balancer also broke off a corner of a brand new Holley while bolting it down:(

[@BigFun4Life]

Can you tell me the part numbers on your th400 “Jtools” for seal installation you use thanks.

[@mountainsgarage]

I will send them tomorrow.

[@mountainsgarage]

Sorry, totally forgot! I am on it!

[@BigFun4Life]

@@mountainsgarage No problem Shawn..Your a busy guy..I haven’t built a transmission in 20 years but I just finished up a mild 6.0 now I need to freshen up a th400 and like you I like tools even if I don’t use them everyday..Thanks again

[@mountainsgarage]

@@BigFun4Life Forward and Direct inner seal protector is J21362, Intermediate Clutch Inner Seal Protector is J21363, and Forward and Direct Outer Seal Protector is J21409. Gear Unit Holding Tool is J21795-02

[@BigFun4Life]

@@mountainsgarage Thank you Shawn..

[@barryacromp6775]

Instead of wd-40 use brake fluid like night and day difference

[@williemccary2462]

Will loose front pump bolts cause no drive an any ranve

[@ericvitelli7113]

Great info- a bad parking pawl will allow car to move on you? I could feel mine creeping.

[@mountainsgarage]

Yes if they get rounded corners they will bypass under load. Click click down the hill!

[@ericvitelli7113]

@@mountainsgarage Thank you. I have an auto -console shift TH400 in my 67 Camaro. 327ME engine out of a 68 Camaro . When it is cold and leaving neighborhood it will go in and out of 1st and 2nd. Otherwise shifts great.

[@mountainsgarage]

@@ericvitelli7113 Cold fluid working on the modulator and governor, pretty normal.

[@alchampion340]

I have a seized modulator valve, in an eight bolt pump case. How much heat should I put on the aluminum to try to work the valve out? It has been sitting for years..

[@mountainsgarage]

In that situation try the least destructive method and hope for the best!

[@alchampion340]

Thanks for the reply , it’s a shame that is an eight boat port case it’s stuck all the way in guess I could fully Manuel the thing.?

[@dermharse9614]

I wouldn't say its a complete loss could tig weld it and have a machine shop touch it up in a big enough boring machine or lathe but then again the machine work cost prob not worth it.

[@rayburton4263]

My transmission sometimes skips 2nd then a slow 3rd. No engine brake on 2nd, I do on 3rd. Sometimes shudders going back to 1st. Any ideas?

[@rayburton4263]

1968 th 400

[@monkeywrenchization]

Weld it up!

[@JaredBell-ne2of]

Can’t build up with a weld and shave it back down to spec?

[@mountainsgarage]

Possible but it is a compound curve. Easy place for a leak. That transmission is back together and in a street rod. It was only broke above the pump O ring. Couple years going now.

[@OkieMike41]

anyone on here know why a th400 would feel weak as if brakes are are partially applied for like 20 seconds first started after sitting? its funny you go to reverse it goes right in gear but feels like it takes more to go maybe its nothing been that way for 3 years???

[@quartermilejunkie5439]

Feels like I just attended a funeral. ;(

[@mountainsgarage]

That is how I feel. More like a wake this morning as I passed the deceased with my head low.

[@quartermilejunkie5439]

@@mountainsgarage LOL!

[@ShawnWasBorn2Ride]

Same

[@truckladders4104]

Could you not build that back with Tig Weld

[@mountainsgarage]

Very possible, a few compound curved sealing surfaces but anything is possible.

[@richardsmith-qy6vl]

What is a ball park price of all the parts needed to build a tùrbo 400 with a trans brake i have a guy who built my turbo 400 its got a manual valve body with a reverse pattern bùt i have anther turbo 400 that ìs a 2 speed it was in my friends69 shevelle that had a 496 blower engine in it and its a fresh transmission and i want to have it set up with a transbrake. Any help would be appreciated

[@mountainsgarage]

If it is a 2 speed TH400 it must already have a transbrake?

[@richardsmith-qy6vl]

@mountainsgarage no it does not have a trans brake it don't even have a manual valve body it came out of my friend 496 blower car he drove it on the street it was really a show car

[@daviddenman7479]

Where are you located? I need a trans built. Probably too far away……but you never know right?

[@mountainsgarage]

Maine, you?

[@daviddenman7479]

@@mountainsgarage Wisconsin. I’m looking to get a th400 build for a turbo 6.0 that I’m putting together.

[@samkaplitz9036]

Could you weld that broken area?

[@mountainsgarage]

Yes, it has multiple curves but possible.

[@robertpaulis439]

Couldn't aluminum weld it and then drill & tap?

[@mountainsgarage]

Yes. It’s a tough spot with compound curves, but I am sure someone skilled could do it.

[@robertpaulis439]

@@mountainsgarage I would suggest that if an attempt is made to bolt a backing plate the full perimeter of the housing to insure against any subsequent warpage.

[@keysautorepair6038]

Just rebuild my th400 now when you put it in gear it won't do anything unless you push the transbrake button then it will work until you shift it to reverse or park then you have to do it again any it acts like it's in drive when you rev it in reverse ideas.

[@mountainsgarage]

What is the valve body?

[@keysautorepair6038]

@@mountainsgarage It's a Hughes reverse pattern HP2215

[@keysautorepair6038]

I pulled it back off cleaned it up nothing seems out of the sorts put it back in and still doing the same thing it didn't start messing up until I tried the transbrake button now it's acting a fool.

[@mountainsgarage]

Maybe the modulator valve is hanging in its bore under the Transbrake solenoid? I see it comes with a spring but should shuttle easy.

[@keysautorepair6038]

@@mountainsgarage I found the issue had a forward clutch piston break odd but I took it back apart it needs aluminum Pistons for sure don't do what I did lol.

[@stevenslater2669]

I broke the upper ear off a C6 once. Still kick myself & it happened almost 50 years ago. Never did it again. Why repeat mistakes when there are so many new ones just waiting to surprise you?

[@mountainsgarage]

Very true!

[@quartermilejunkie5439]

I say and know for a fact that I became a real good wrench because I made so many mistakes pushing the limit...45 years and counting.

[@mountainsgarage]

@@quartermilejunkie5439 Nice! Great outlook!

[@alexowen5045]

Couldn’t it be welded? I don’t have much experience

[@mountainsgarage]

It could, but with compound angles it might make it worse. I ended up building myself a bomb of a transmission for a Rat Rod. It will likely never bother.

[@vrg69]

What do you charge for a built th400

[@mountainsgarage]

They are all around $2000ish

[@22jefferysmith15]

My truck will go into reverse and it will go at a idle can you please help me I have a Chevrolet truck a 1990

[@mountainsgarage]

Glad to help, just need more info?

[@22jefferysmith15]

My truck will back up at a idle but if I hit the throttle it just spins

[@mountainsgarage]

@@22jefferysmith15 How about forward, is it missing any forward gears, What transmission?

[@22jefferysmith15]

It's a th400 all forward gears work

[@sewerpipecasso8750]

New video = BREAK TIME

[@williemccary2462]

Rang