TH400 Information Thread

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NickTransmissions

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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!
Hey Bob - some of the HD and HP TH400s/475s had 6 frictions and steels in the direct clutch along with 5/5 in the forward...Post 73, they used stamped steel apply pistons with selective apply rings so it's very easy to fit an additional friction and steel by swapping out apply rings to short ones for each drum. Everything else is the same so you just need to raid your local hard parts suppler (or eBay) for the apply rings that you need to add those additional clutches to your packs and you're good to go. Most of the high performance muscle car stuff got either 5 or 6 direct clutch frictions. For aluminum pistons, you can either machine your pre-existing piston or look for one of the pistons with the letter code corresponding to a 5 or 6 clutch stack, if that's what you'd like to build.

Here's a quick ref table that shows the various stamped steel and aluminum piston and clutch configurations over the years, as taken from my TH400 fast facts doc. Note the codes for the 6-clutch stack ups. That stuff will install into any TH400 as long as you have the right parts as shown below.
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Clutch pack clearance is still .010" per friction, per General Motor's guidelines; forwards can be a bit tighter than direct.

My TH475 Assembly PT1 video shows a factory 5 clutch fwd drum and 6-clutch direct drum for reference.
 

Matt69olds

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The OW and BB calibration (I wouldn’t be surprised to find Pontiac and Chevy had their own codes for basically the same transmission) used a unique valve body, a 6 clutch direct drum with no wave plate, and probably a specific govenor. Some of this is outlined in the factory service manual, some from articles written my the engineer at HydraMatic who was in charge of the special calibration. Can’t remember the guys name.

You might find this interesting:

 

NickTransmissions

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The OW and BB calibration (I wouldn’t be surprised to find Pontiac and Chevy had their own codes for basically the same transmission)
Yep, they did or at least the clutch pack config was the same across the Chevy/Pontic vs Olds and HP Buick turbo 400s; many of those VBs had no spring in the 1-2 acc reg valve, no lip seal in the forward drum along with no wave in the direct, as you mentioned. Most had 12 springs in the int clutch with three flat steels vs the bottom waved cusion steel under the first friction...There may have been other differences but dont know them off hand.
 

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The OW and BB calibration (I wouldn’t be surprised to find Pontiac and Chevy had their own codes for basically the same transmission) used a unique valve body, a 6 clutch direct drum with no wave plate, and probably a specific govenor. Some of this is outlined in the factory service manual, some from articles written my the engineer at HydraMatic who was in charge of the special calibration. Can’t remember the guys name.

You might find this interesting:

My W-30 currently has a PW trans w/performance mod's. She shifts aggressively & barks them in all gears. Somewhere, somehow in it's travels, the OW magically got swapped out & none of the PO's knew how. I did manage to purchase a correct '70 OW that had been pulled and put in storage, sounded like it came out of a wrecked W-30. Supposedly, it has been gone through & re-sealed. I bought it from an Old's guru on the east coast, so I know the story is legit. I'm going to vin stamp it to my vin when I finally install it as SOMEBODY has my original OW trans that shouldn't have.
 

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I have been searching for the unique 1-2 modulator valvetrain setup for my car to duplicate the automatic 3-1 downshift. As many high performance transmission builders there are, I have no doubt a bunch get thrown away when machining stock valve bodies for transbrake and reverse manuals. I’d be willing to bet I tossed out many when I worked at Coan years ago.

I can’t find the interview, but Denny Manner (one of the engineers at GM Powertrain and the head engineer at Buick) said he got a lot of grief from HydraMatic when he asked for the WOT 3-1 downshift capabilities for the Stage 1 and W-30 cars, they had no interest in building a valve body with that calibration. But he did go on to say that one big reason the cars had such a vicious reputation on the street.

I have a 4L80 I built to put in my car, don’t know if I’ll ever get around to it. I have zero doubt as soon as I do, I’ll find a transmission core with that valvetrain setup. If that happens, I’ll be sure to let you know.
 

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I was wondering if anyone has used a four speed Hydramatic trans and tossed the turbo 350/400 from their truck?

I did just that ..
 

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dragstews

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Have you had a chance to drive it? How's it working out?
Still working on the installation ...

Not a Plug & Play deal for a 4x4 ..
Shafts, crossmember, column shift lever pivot bracket and dealing with making a mount up to relocate the NP203 shifter ..
Two wheel drive is much less complicated ...
 

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You're welcome, @Sgt Gus!

Keep an eye on it, note that if your shifts start becoming late and real harsh, that could be a sign of high line pressure, which is common in these units as they wear/age...A pressure test can quickly rule that in or out.
What about softer shifts? When I got the truck in 2012 it slammed into reverse, but not so much into drive, and it shifted softly and quickly. So I replaced the modulator valve, and have done a few drain and fills, one was because I inadvertently got the wrong filter, and that was maybe 2015 or later. When I installed it I saw material inside it. I later learned it was the dacron style, and after a few weeks I found the good filter. With the dacron filter I could here the pump, after swapping out the dacron it was back to normal sounds. But, the shifting isn't as pronounced as it used to be, and often when going from P, R, or N into D, D will slip. But, if shifted into 2 and back to D it'll usually operate fine. Shifting into 1 and then 2 it'll shift more solidly into 2, back not so much going into D. And if taking off from D (when it's operating like it should), 1 to 2 is soft, sometimes not noticeable, and sometimes it shifts quickly from 1 to D without feeling any shift at all.

Because of the issues with this truck over the years, I haven't driven it much, which may be part of the cause. Last night I poured some seafoam hydra trans tune in it, but I noticed that stuff is super thin. After I added the trans tune(about 2 miles from home), I went to a parking lot next to the house, and for about 10 minutes shifted back and forth from R to D without giving it any throttle most of the time. Since I was not consistent on the amount of time in R or D, I wasn't staying in the same area, so I did have to give it a little throttle to either go further back to avoid going into the street, or further forward to avoid hitting the fence. In R it engages strong, like it does when it's shifted into 1 or 2. On the occasions that I gave it more throttle in D to get away from the fence, it slipped and tried to engage more but never felt strong like the other gears.

When it's cold, and I have to sit at the light, I leave it in N and raise the rpms until the light turns green. If I just put it in D it'll slip badly, so I usually shift all the way into 1, then 2, and sometimes when shifting into D it'll slip, so I have to shift back into 2 and then to D. That usually engages D, but it has slipped before, needing another drop into 2 and back into D.

Do you think the trans is shot, or on its way out, or just varnished? I am certain it's all original, as everything I have taken apart has been the first time for this truck, i.e.: carb, shift linkage, resealing engine, etc. Last night I also changed the modulator valve to see if it helped with the shifting points and it did not. I have gone 2 turns in after installing the new modulator valve.

I hope you read this and can respond. If you need additional information, let me know. Thanks.
 

NickTransmissions

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What about softer shifts?
@DoubleDingo - Yank and overhaul the unit...Sounds like all of your applied elements are worn but will be important on tear down to determine if the wear is simply normal for the mileage and usage pattern or if there are other causes like hard part wear/damage...Inspect the lip seals, their respective surfaces, sealing rings, etc...

The reason you have more positive engagement when manually shifting is that when in Low Reverse (1) and Manual Second (2), line pressures are higher and you have both bands working in each respective position, in addition to the forward and intermediate clutches...When in Drive, only the forwards (in 1st gear) and intermediates (in 2nd gear) are working...Many hands make for lighter work but you shouldn't be slipping at all when in Drive, especially after you gave it a service and changed/adjusted the modulator.

Let me know if you have any addl questions about the rebuild, parts selection, procedures and other aspects of overhaul and I'll respond when I can.
 

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@DoubleDingo - Yank and overhaul the unit...Sounds like all of your applied elements are worn but will be important on tear down to determine if the wear is simply normal for the mileage and usage pattern or if there are other causes like hard part wear/damage...Inspect the lip seals, their respective surfaces, sealing rings, etc...

The reason you have more positive engagement when manually shifting is that when in Low Reverse (1) and Manual Second (2), line pressures are higher and you have both bands working in each respective position, in addition to the forward and intermediate clutches...When in Drive, only the forwards (in 1st gear) and intermediates (in 2nd gear) are working...Many hands make for lighter work but you shouldn't be slipping at all when in Drive, especially after you gave it a service and changed/adjusted the modulator.

Let me know if you have any addl questions about the rebuild, parts selection, procedures and other aspects of overhaul and I'll respond when I can.
Thank you for your speedy reply.

That's what I thought you would say. Is it okay to drive it like this until I get the parts to rebuild it? If I opt to try the rebuild myself, do I have to clean the entire case, or can I just make sure the internals are cleaned? Granted, I would scrub and clean the outside the best I can before tearing it down. I can always see if Pop is willing to help me, but I don't know if he's wanting to do this stuff anymore.

This being a work truck, and no more power adders will be installed, what kit/parts do you recommend? I need to order them sooner than later.
 

NickTransmissions

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Thank you for your speedy reply.

That's what I thought you would say. Is it okay to drive it like this until I get the parts to rebuild it? If I opt to try the rebuild myself, do I have to clean the entire case, or can I just make sure the internals are cleaned? Granted, I would scrub and clean the outside the best I can before tearing it down. I can always see if Pop is willing to help me, but I don't know if he's wanting to do this stuff anymore.

This being a work truck, and no more power adders will be installed, what kit/parts do you recommend? I need to order them sooner than later.
You're welcome - the below video should address all of your questions and then some - it's of my TH475 build up but otherwise is identical to how I'd build yours, other than maybe dual feeding the direct clutch (I didn't do that in the video) but it's very easy. Hot tank the case and all aluminum parts; clean ferrus metal parts with whichever solvent but don't dry the planetary carriers with shop air - just wipe them down and dry them off.

Dual feed: Leave out direct drum center seal, 2nd from the top sealing ring off the center support, plug the high-reverse feed passage in the case using a 3/8" cup plug and loctite (the hole to the right of the intermediate clutch feed bolt) and drill out the 2-3 feed hole about 10% or so wider than stock to start. Everything else about the rebuild is the same, procedure wise.

Parts can be sourced via your local hard parts supplier or online (eBay has some good 'Deluxe Kits' that come with everything you'll need - just search TH400 Deluxe Kit).

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You're welcome - the below video should address all of your questions and then some - it's of my TH475 build up but otherwise is identical to how I'd build yours, other than maybe dual feeding the direct clutch (I didn't do that in the video) but it's very easy. Hot tank the case and all aluminum parts; clean ferrus metal parts with whichever solvent but don't dry the planetary carriers with shop air - just wipe them down and dry them off.

Dual feed: Leave out direct drum center seal, 2nd from the top sealing ring off the center support, plug the high-reverse feed passage in the case using a 3/8" cup plug and loctite (the hole to the right of the intermediate clutch feed bolt) and drill out the 2-3 feed hole about 10% or so wider than stock to start. Everything else about the rebuild is the same, procedure wise.

Parts can be sourced via your local hard parts supplier or online (eBay has some good 'Deluxe Kits' that come with everything you'll need - just search TH400 Deluxe Kit).

xc_hide_links_from_guests_guests_error_hide_media
Thank you very much!
 

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Good stuff guys! :)
 

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