TH400 Information Thread

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AuroraGirl

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Yes, there are for sure different dipsticks. Not sure how many, there are many though since they're intended for many different model cars, trucks, vans, RV's etc

There is a deep pan and a shallow pan, and the difference is very obvious. One is I'd say an inch deepl the other usually found on trucks is close to 3 inches deep. So if yours that you compared looked the same, then they are the same.

Awesome for you and the variable pitch Th400. I had a VP Th400 out of a 67 Olds that was behind an Olds 425. I wanted to use it too just for the cool factor of having 2 different stall speeds. I wanted to make a street/strip truck and use a toggle switch for close to stock stall, and hit the switch and go into about a 3000 stall. Well, as many awesome awesome projects and opportunities I've had with cool parts, that I had to sell to make ends meet, those parts got sold on eBay for about 5 times what I paid for them, not to mention all the other spare parts I had too. But yeah, get that done and let us know how it goes. I had trouble finding someone that build my converter the way I wanted it built and I knew it would be expensive if I did find someone, so that was part of the decision in selling the parts to someone who may have already had the converter they wanted.

What is sittting for an extended period? You know an older transmission that sits for several months or years will tend to harden the seals in the clutch drums and such and it won't move. After warming up a bit, you might get a little action out of it as the seals soften just a bit. If that's the case, I've had some real good luck in the past by adding a trans additive. I know I know, I too had additives to anything, engine, trans, anything, but I have to say, it's been more than once or twice where I've seen additives help an auto trans that sat for quite some time. The additives seem to soften the seals and make them a bit more supple and pliable to where the transmission will work again. I'll also add, if it does work out, don't have high expectation for a long lived transmission. But hopefully, it'll be patch job to get you by for a couple to a few months to when it's a better time to get a rebuild done. You can add 1 bottle and see what happens. If it's needs 1 more, go for it. If 2 bottles don't do it, then give it up, it's not going to work this time.
seafoam trans tune?
 

HotRodPC

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seafoam trans tune?
That's a good one, Lucas is a good one. IIRC, it was Lucas I used for a truck I bought that didn't move and I ended up driving it home just fine. There's other good ones too. I think just about any Trans Conditioner additive does it. I do like SeaFoam Trans Tune though. Really, I"ve never been big on additives at all. Always called them witch potions or snake oil. Think about it, engine oils and fluids are formulated in a lab for a reason. Now you go adding things to these fluids and oils, you just destroyed all the work done in the lab when that product was designed and formulated right? I don't even like adding different engine oil between oil changes. If I put Valvoline High Mileage 5w 20 in the car at oil change, I don't add a quart of Penzoil 10W 40 3000 miles later cuz it's showing to add a quart. I will to get home in a pinch, if that's all I can get it's all I can get so I'll save the engine. But then it gets a full oil and fitler change. So NO, I have never liked additives, but being I was in situations where I had nothing to lose, I did add some snake oil to the auto trans, and it did work. My SIL's 700r4, he added a bottle, it helped some but not quite, he added another bottle and it was much better. He babied it for a couple days even though it was working very well, and I told him, don't hold your breath, it's not going to last very long. He ended up getting 10 months out of it and he beat the living hell out of it and drove it daily all day long. Many many miles were put on it in that 10 months. I was truely shocked but impessed. Especially for a 700r4. Fluid was dark and nasty and I did tell him, DO NOT CHANGE that fluid. It'll be lights out forever if you do, so he didn't, but he did the 2 bottles of additives and it revived it with that nasty fluid.
 

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Drop the pan again, look at the dipstick. The “Full” mark should be level with where the pan and case meet.

When you replaced the filter, did you remove the filter tube from the case? There is a Oring that seals the tube to the case, if it’s missing or damaged the pump will suck air instead of fluid.

I agree with nick, get a line pressure gauge on it and see what the pressures are. Then you will have a better idea of what to do next.
 

AuroraGirl

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That's a good one, Lucas is a good one. IIRC, it was Lucas I used for a truck I bought that didn't move and I ended up driving it home just fine. There's other good ones too. I think just about any Trans Conditioner additive does it. I do like SeaFoam Trans Tune though. Really, I"ve never been big on additives at all. Always called them witch potions or snake oil. Think about it, engine oils and fluids are formulated in a lab for a reason. Now you go adding things to these fluids and oils, you just destroyed all the work done in the lab when that product was designed and formulated right? I don't even like adding different engine oil between oil changes. If I put Valvoline High Mileage 5w 20 in the car at oil change, I don't add a quart of Penzoil 10W 40 3000 miles later cuz it's showing to add a quart. I will to get home in a pinch, if that's all I can get it's all I can get so I'll save the engine. But then it gets a full oil and fitler change. So NO, I have never liked additives, but being I was in situations where I had nothing to lose, I did add some snake oil to the auto trans, and it did work. My SIL's 700r4, he added a bottle, it helped some but not quite, he added another bottle and it was much better. He babied it for a couple days even though it was working very well, and I told him, don't hold your breath, it's not going to last very long. He ended up getting 10 months out of it and he beat the living hell out of it and drove it daily all day long. Many many miles were put on it in that 10 months. I was truely shocked but impessed. Especially for a 700r4. Fluid was dark and nasty and I did tell him, DO NOT CHANGE that fluid. It'll be lights out forever if you do, so he didn't, but he did the 2 bottles of additives and it revived it with that nasty fluid.
nice. I helped my e4od along a lot because it originally had Type F in it when I started using it because it puked its fluid on the road for my grandparents a long time ago and my uncle stopped at a gas station and grabbed type F.. And I didnt know that was not proper fluid., So when I learned it wasnt. I used some trans tune for a bit before i ended up dropping pan. I ended up having it puke fluid more than 4 times at at least 4 quarts each, I saw it as an opportunity to flush it with normal fluid lol... fixed the cooler situation(restricted cooler caused the issue) and then did pan drop with right fluid. Was dark and sadly had some bits of metal... and I no longer can move forward in drive, but i can put it in 1 or 2 and then shift up into Drive lol....

but it did help!

I have gotten a LOT of good luck using trans tune in power steering systems. My ford C2 pump is still a whiny bitch but its much improved. The saginaw in my square is quiet and smooth from using it, and I successfully fixed my 2001 auroras ps system which was severely gummed up with the trans tune,m and I use it in everything else especially leading up to a flush. Youll notice the fluid becomes dark but not like old transmission dark. I think it cleans that varnish and gummy build up and then it suspsends in the fluid .
 

Fat 454

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Hi Nick and all, who are your recommended go to suppliers for T400 service parts ? I will also note that I am not in the continental US, so will need to mail internationally, however we get all our other parts that way so no big deal. Use Rock Auto for a lot of stuff, as well as the usual LMC etc. however looking for recommended trans parts suppliers please? -
Project is the T400 in my son's ( new to us ) 80's C30 454 TBI dually - no reverse, sat for ages. Plan is to find a suitable rebuildable unit, strip it, full rebuild, and then swap into the truck.
All help appreciated, and yes, will post pics of what we find if anyone is interested. Thanks !..
 

Fat 454

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Also interested in anyone's list of "must have" upgrades for reliability - ( shift kit, clutches, HD C clips etc. ) - truck will be stock ( changing from dually axle to SRW ) , and just used for normal truck stuff - highway hauling and some towing. No racing or tractor pulls !! Oh, and its a crewcab too. Thx.
 

NickTransmissions

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Hi Nick and all, who are your recommended go to suppliers for T400 service parts ? I will also note that I am not in the continental US, so will need to mail internationally, however we get all our other parts that way so no big deal. Use Rock Auto for a lot of stuff, as well as the usual LMC etc. however looking for recommended trans parts suppliers please? -
Project is the T400 in my son's ( new to us ) 80's C30 454 TBI dually - no reverse, sat for ages. Plan is to find a suitable rebuildable unit, strip it, full rebuild, and then swap into the truck.
All help appreciated, and yes, will post pics of what we find if anyone is interested. Thanks !..
Since you're outside CONUS, best bet is probably eBay or perhaps Amazon. I like the kits sold by Transparts Warehouse (ebay search: "TH400 Deluxe kit); most come with upgraded Alto high energy clutches, new steels, both bands, paper/rubber kit, bushings, filter, etc.

For a stock build, you dont need much when it comes upgrades. Install a Sonnax boost valve kit in place of the factory boost valve. Check pump gears and clearance; machine the pump if necessary. Rollerize the rear of the case (see my TH400 or TH475 rebuild video for the parts and procedures).

Dont need a shift kit. If you want to crispen/firm up your shifts, just drill the 1-2 and 2-3 feed holes out by about 10% larger each. If your valve body has a spring outboard of the 1-2 accumulator valve, leave it out. Put a Chrysler A518 direct clutch snap ring in place of the factory snap ring for your intermediate clutch. There's six different thicknesses avail but you will likely need either the .088 or .098 version. Purchase new intermediate and low-roller one way clutches. Install a Sonnax billet, rollerized forward hub if you think it will see very heavy duty use..

New torque converter, new detent solenoid, new governor gear. Move the drive/driven gear from your existing trans to the new one during overhaul.
 

HotRodPC

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Since you're outside CONUS, best bet is probably eBay or perhaps Amazon. I like the kits sold by Transparts Warehouse (ebay search: "TH400 Deluxe kit); most come with upgraded Alto high energy clutches, new steels, both bands, paper/rubber kit, bushings, filter, etc.

For a stock build, you dont need much when it comes upgrades. Install a Sonnax boost valve kit in place of the factory boost valve. Check pump gears and clearance; machine the pump if necessary. Rollerize the rear of the case (see my TH400 or TH475 rebuild video for the parts and procedures).

Dont need a shift kit. If you want to crispen/firm up your shifts, just drill the 1-2 and 2-3 feed holes out by about 10% larger each. If your valve body has a spring outboard of the 1-2 accumulator valve, leave it out. Put a Chrysler A518 direct clutch snap ring in place of the factory snap ring for your intermediate clutch. There's six different thicknesses avail but you will likely need either the .088 or .098 version. Purchase new intermediate and low-roller one way clutches. Install a Sonnax billet, rollerized forward hub if you think it will see very heavy duty use..

New torque converter, new detent solenoid, new governor gear. Move the drive/driven gear from your existing trans to the new one during overhaul.
Have you ever used these guys Nick??? I've had real good luck with these kits and prices are not bad either. I'd imagine you might do better since you likely buy in bigger volume.
There kits have always been all the famous name brand seal kits and clutchs, Borg Warners, Alto etc. I aslo like they have an option to get the waffled cltuches for a Th400 which I normally get. https://www.transmissionpartsusa.com/Default.asp <<< Link to Transmission Parts USA out of Florida. Their shipping is fairly quick too depending on what day of the week it gets out. Seems if I ordered by Noon central time, it would go out the same afternoon and I usually had it 2 days later via UPS ground.

Yep, not much needs done for a stock or very mild, like for an RV, not much needs done to a Th400. They are reliable and strong in OEM form.
 

NickTransmissions

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Have you ever used these guys Nick??? I've had real good luck with these kits and prices are not bad either. I'd imagine you might do better since you likely buy in bigger volume.
There kits have always been all the famous name brand seal kits and clutchs, Borg Warners, Alto etc. I aslo like they have an option to get the waffled cltuches for a Th400 which I normally get. https://www.transmissionpartsusa.com/Default.asp <<< Link to Transmission Parts USA out of Florida. Their shipping is fairly quick too depending on what day of the week it gets out. Seems if I ordered by Noon central time, it would go out the same afternoon and I usually had it 2 days later via UPS ground.

Yep, not much needs done for a stock or very mild, like for an RV, not much needs done to a Th400. They are reliable and strong in OEM form.
They look/sound familiar, perhaps they're on eBay or sell via Amazon...If they provide kits w/Alto, BW, Raybestos, etc friction elements they should be good to go...Most of my soft parts are either sourced locally via Transsttar's distributor here in town or distributors out of Cali. Transstar (for some Sonnax parts), Summit Racing, CK Performance, Cope Racing, Circle D, etc for special order, high $ billet stuff.
 

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thanks guys - appreciated. I will look them up and see what their shipping is like. As said, will probably buy a core and do a full rebuild and then swap them out. I'll report back how it all goes. Oh, by the way a "rebuild " core here is around A$1,500.....
 

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They look/sound familiar, perhaps they're on eBay or sell via Amazon...If they provide kits w/Alto, BW, Raybestos, etc friction elements they should be good to go...Most of my soft parts are either sourced locally via Transsttar's distributor here in town or distributors out of Cali. Transstar (for some Sonnax parts), Summit Racing, CK Performance, Cope Racing, Circle D, etc for special order, high $ billet stuff.
I have a Transtar here local in OKC and still use that Transmission Parts USA usually due to prices. They also carry most Sonnax parts.
 

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Question about a recent issue with loose bolts that connects the torque converter to the flex plate, 1 was loose. So loose that there was play enough to move the torque converter by hand just a little. Does anyone know the specific torque on those bolts? I’m not sure if tightening them and testing it is smart.
 

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Question about a recent issue with loose bolts that connects the torque converter to the flex plate, 1 was loose. So loose that there was play enough to move the torque converter by hand just a little. Does anyone know the specific torque on those bolts? I’m not sure if tightening them and testing it is smart.
When they came loose was it a horrific sound lol?
Could use some blue lock-tite on it. I'm sure there is a torque for it but I've never torqued those before. Just goot-n-tite and sometimes some blue and call it good.
 

NickTransmissions

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Question about a recent issue with loose bolts that connects the torque converter to the flex plate, 1 was loose. So loose that there was play enough to move the torque converter by hand just a little. Does anyone know the specific torque on those bolts? I’m not sure if tightening them and testing it is smart.
Like mentioned above, use blue Loctite and torque to 35-40 ft lbs, though I'd replace those particular bolts with a set from ARP, given that they were loose across multiple drive cycles. The ARP bolts take 50 ft lbs when using their fastener assembly lube.
 

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Like mentioned above, use blue Loctite and torque to 35-40 ft lbs, though I'd replace those particular bolts with a set from ARP, given that they were loose across multiple drive cycles. The ARP bolts take 50 ft lbs when using their fastener assembly lube.
A bit off topic here Nick, but I was wondering about your knowledge of the OW trans used in the '70 W-30's, compared to other Olds & RARE Buick applications. I understand the during the GM strike of late 1970, that some OW's were installed into the GS Buicks on accident, due to unknowledgable strike scabs(haha!) I know the W-30's had specially built clutch packs, do you know in comparison if they were indeed built differently than the standard OW's that were used well into the mid-late '70's? They started using the OW's in the '68 442's also, just wondering how many versions of the OW that you know of? Appreciate your insight on this!
 

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