[chiphead]

So I want to put a Transgo shift kit in my TH400. I don't know the year of the trans or what's been done to it. It does shift like it's had some work done to it. The shifts are firm, but inconsistently so. I can't feel it downshift as I approach a red light. It does have a torque converter that's on the loose side. I've already checked the modulator and governor.

How do I tell if it's had the direct dual feed mod done internally, without pulling the trans? The TG shift kit dual feeds the direct using a separator plate. Supposedly it doesn't play well if the direct is dual fed by removing stator rings or lip seals. Is there anything I can look for when dropping the valvebody?

If I can't tell if the internal dual feed mod has been done, should I retain the stock separator plate, open the holes to match the TG plate and use the TG springs in the VB?

[65 Lamnas]

Originally Posted by chiphead

So I want to put a Transgo shift kit in my TH400. I don't know the year of the trans or what's been done to it. It does shift like it's had some work done to it. The shifts are firm, but inconsistently so. I can't feel it downshift as I approach a red light. It does have a torque converter that's on the loose side. I've already checked the modulator and governor.

How do I tell if it's had the direct dual feed mod done internally, without pulling the trans? The TG shift kit dual feeds the direct using a separator plate. Supposedly it doesn't play well if the direct is dual fed by removing stator rings or lip seals. Is there anything I can look for when dropping the valvebody?

If I can't tell if the internal dual feed mod has been done, should I retain the stock separator plate, open the holes to match the TG plate and use the TG springs in the VB?

Drop the valve body and take a look at the separator plate. If it's already had a TG kit, you'll notice it on the plate. You're not going to be able to tell if it's had rings or lip seals removed unless you look, which involves removing the trans. If it was me in your shoes, I'd pull the trans and disassemble it to see what's been done. Is there no tag riveted to the case? If it's there, look at the 2 digit date code. Otherwise you can sometimes ID the gen of the case by the type of hard parts already in it....of course that could all be "out the window" if someone has transplanted a bunch of parts.

I'm finishing up a TH400 for my '65 Lamnas which is a 1966 case. I upgraded to the "later" center support and made a few add'l mods along the way for shorter shifts, longetivity and higher torque load capacity

[chiphead]

I hear you, I'll freshen it when this motor comes out in the next year or two. But I'd like to open it up, change the filter and see if its healthy. If not, I'll need to do the motor swap sooner than later.

On a performance street TH400, do you guys block the 2-3 accumulator or not? What feed hole sizes do you use? It shifts like it's been set on kill, even with a loose converter. I may ask about dialing it back a bit, depending on what I find.

[65 Lamnas]

Originally Posted by chiphead

I hear you, I'll freshen it when this motor comes out in the next year or two. But I'd like to open it up, change the filter and see if its healthy. If not, I'll need to do the motor swap sooner than later.

On a performance street TH400, do you guys block the 2-3 accumulator or not? What feed hole sizes do you use? It shifts like it's been set on kill, even with a loose converter. I may ask about dialing it back a bit, depending on what I find.

Someone's maybe enlarged the 3rd feed hole in the sep. plate Your 2-3 shift is mostly dependent on that, If it feels like both shifts are "set on kill", someone previous might've boosted the line pressure with a stiffer regulator spring, so maybe check that first. That would be accessible after pulling the pan. Original PR springs are normally blue in color, the higher pressure springs are normally orange. Should be no shims with the orange spring,

I usually put the 1-2 feed hole at about .090"-.100" and the 2-3 feed about .085" depending on other things within the VB. You can also tune that shift (1-2) with springs in the VB, which changes accumulator pressure

Also, someone might have previously messed with the VB springs for the 1-2 accumulator...so there's that possibility, too.

[Cliff R]

First test the unit to see if it's had the 1-2 shift valve mod done to it. If so it will stay in 1st and not upshift to 2nd no matter what, and it will go to 1st at any vehicle speed. You don't have to get crazy with that test, the manual low control mod just puts or keeps the trans in low gear no matter what.

You may see one of the feed holes to the center support blocked if it doesn't have the Transgo direct double feed modification.

As mentioned you'll have to take the trans apart to see if the center seal has been removed from the direct apply piston and sealing ring removed from the center support to double feed.

ALWAYS be conservative with separator plate hole sizes, especailly if the PR spring has been shimmed or replaced for higher line pressure. It's pretty easy to get "window shattering" shifts from a TH400 if you go right to the larger end of the spectrum with hole sizes in the plate.

Modding the 2-3 accumulator has never had any negatives that I've seen. Hitting 2nd gear really hard is NEVER a good idea and the best way I know to bust up the sprag (or roller clutch) on the 1-2 upshift if/when you find good traction and have high HP.......

[kyle_blake]

cliff - i can attest , my car whoever built the th400 made the 1-2 shift even when light throttle in drive , made it shift like my rear end went kir bang. i was like jesus. so i always manually shifted and made sure i was accelerating into second gear. it was always fun getting second gear rubber chirp. never knew cars could do that. annoying to always have to manually shift a stock ratchet shifter. fast forward years go by. i go to shift into second it makes the shift then "flies" into Neutral. which sends the RPM's way up. so of course what would any driver do- let off gas... then of course it ends up still driving. i get it rebuilt and someone is like there is no proper shift kit in it like transgo, some i dunno drilled this or removed check balls that. never did know exactly.... i said was anything wrong? they said it even had the HD 34 element sprag? in it. They showed me it. he said all the bands were good. here you go sir, $1600 dollar rebuild. so $34 part. now a days anything for $1600 bucks is a good repair!

LOL

the transgo set to lightest setting is a nice jump from 1-2 WOT but nothing like it was before and 2-3 is just a normal 2-3 shift.

adjustable vac mod is nice. delays some part throttle shifts , neat to see how car reacts with it.

all behind the jim hand 3000 stall i got done years ago.

[chiphead]

Does anybody have a line pressure chart for a stock TH400, along with test method?

Can you believe I've drug the internet for a few days and cannot find a stock test procedure and chart? It's all transbrake pressures in rocketships.

[400 Lemans]

Pressure chart for t-400 on post #14.https://classicoldsmobile.com/forums...-wrong-141533/

[65 Lamnas]

Originally Posted by chiphead

Does anybody have a line pressure chart for a stock TH400, along with test method?

Can you believe I've drug the internet for a few days and cannot find a stock test procedure and chart? It's all transbrake pressures in rocketships.

Probably going to hell for this, but I copied this out of the TH400 bible (sorry Cliff).

0-300 psi gauge works well for this

[chiphead]

Thanks for the charts!

I let the engine warm up for a few minutes then checked line pressure. Here are my TH400 pressures as it sits, before I change anything.

With vacuum modulator connected, 12" at idle, 15" at 1000 RPM

Park at idle 135 PSI
Park at 1000 120 PSI

Rev at idle 210 PSI
Rev at 1000 210 PSI

Neutral idle 135 PSI
Neutral 1000 125 PSI

Drive idle 135 PSI
Drive 1000 135 PSI

Low idle 180 PSI
Low 1000 190 PSI

The online data says that pump pressure should be limited to 160PSI. I guess that explains a lot about the shift quality! What modifications should I do, to help it live until I pull it out and rebuild?

[65 Lamnas]

Originally Posted by chiphead

Thanks for the charts!

I let the engine warm up for a few minutes then checked line pressure. Here are my TH400 pressures as it sits, before I change anything.

With vacuum modulator connected, 12" at idle, 15" at 1000 RPM

Park at idle 135 PSI
Park at 1000 120 PSI

Rev at idle 210 PSI
Rev at 1000 210 PSI

Neutral idle 135 PSI
Neutral 1000 125 PSI

Drive idle 135 PSI
Drive 1000 135 PSI

Low idle 180 PSI
Low 1000 190 PSI

The online data says that pump pressure should be limited to 160PSI. I guess that explains a lot about the shift quality! What modifications should I do, to help it live until I pull it out and rebuild?

Seems quite high everywhere. Disconnect the electrical wire going to the detent solenoid (driver's side wire) and rerun the pressures. If the pressures all drop and check out normal, then you've isolated it....if not, then it's something with the modulator or PR, and both are accessible after dropping the pan. Do you have the original large black modulator or the small gold colored modulator with a red or black stripe or no stripe?

[chiphead]

Detent wire isn't hooked up at all. I've fixed the wiring, but haven't hooked it up yet. The modulator is an aftermarket red stripe. I removed the modulator and checked it and the adjustment. I noticed the spool valve won't slide fully out of the case. So I need to get that guy out when I drop the pan.

But the regulator in the front pump sets max pressure, correct? Even if the modulator was stuck in full line position, the 200+ PSI is coming from the regulator, yes?

So I need to pull the valvebody off and inspect, yes?

[65 Lamnas]

Originally Posted by chiphead

Detent wire isn't hooked up at all. I've fixed the wiring, but haven't hooked it up yet. The modulator is an aftermarket red stripe. I removed the modulator and checked it and the adjustment. I noticed the spool valve won't slide fully out of the case. So I need to get that guy out when I drop the pan.

But the regulator in the front pump sets max pressure, correct? Even if the modulator was stuck in full line position, the 200+ PSI is coming from the regulator, yes?

So I need to pull the valvebody off and inspect, yes?

On a TH400 that's not been apart or maybe one that's had a basic stock-type rebuild without any major performance enhancements (like a shift kit).....it's really more likely something with the modulator than the PR system. But since history is unknown, that's sorta out the window....

But you've checked for sufficient vacuum and verified it's reasonable (manifold vacuum, NOT ported) and there's no vacuum leaks in the line to the modulator...RIGHT? and I know you said you checked and adjusted the modulator....but they are relatively cheap....maybe try replacing it? The fact that the modulator spool valve "won't come completely out" is not a shocker. As long as it moves throughout its normal range freely, it's probably fine. But try a pencil magnet to remove it from its bore if you're in there. If that wont do it, then you'll have to wait til the pan's off

It could be something with the PR system, and the chances of that increase cuz you don't REALLY know what was done previously, like if the spring was changed, or if somebody has swapped the PR spool to the wrong one ('71-later don't have an orifice). The PR boost valve could be sticking, too. Maybe there's a wear issue that's causing something in the PR bore to stick?

I'm trying to say....eliminate the stupid, easy stuff by checking for a vacuum leak in the modulator line, try replacing the modulator ($20), before pulling the pan....If you DO have to get into the PR without pulling the trans, it's kinda a PITA with the PR spring which is loading the snap ring, and fluid dripping down your arms and gravity, etc....Have some brake cleaner ready, some trans-gel or vaseline, and some emery cloth for the bore. It's easy to lose or drop ****. There might be spring shims in there and there should be a spring seat....try to be careful as it's coming apart so you know how everything was in there, cuz that's actually good evidence. It's all just harder to do with the trans in the car... especially if you don't have the luxury of a lift while working on it......good luck, buddy....post pics here if you get in a jam or have component questions.

[chiphead]

I was planning on doing a shift kit and swapping the loose converter for a 10" continental Jim Hand I have. I could put the stock pressure regulator spring back in it. But I'm now concerned about causing thrust bearing or converter issues.

What's the chance the converter feed has been restricted? Would reducing line pressure from 210 to 160PSI cause converter feed issues, if a restriction had been installed? This trans has been in service for several years, possibly as many as 25. The car was restored in the 1990s but I have no records. The engine and trans are painted the same color blue, so they were installed together. The trans tag is missing.

The main issues with this setup are:
Loose torque converter, it'll flash to 4000.
No part-throttle downshifts
Very firm upshifts, likely too hard with a Continental converter.

Basically, should I roll the dice and modify this unit, or just find another TH400 and start fresh? If so, what years should I look for?

[65 Lamnas]

Originally Posted by chiphead

I was planning on doing a shift kit and swapping the loose converter for a 10" continental Jim Hand I have. I could put the stock pressure regulator spring back in it. But I'm now concerned about causing thrust bearing or converter issues.

What's the chance the converter feed has been restricted? Would reducing line pressure from 210 to 160PSI cause converter feed issues, if a restriction had been installed? This trans has been in service for several years, possibly as many as 25. The car was restored in the 1990s but I have no records. The engine and trans are painted the same color blue, so they were installed together. The trans tag is missing.

The main issues with this setup are:
Loose torque converter, it'll flash to 4000.
No part-throttle downshifts
Very firm upshifts, likely too hard with a Continental converter.

Basically, should I roll the dice and modify this unit, or just find another TH400 and start fresh? If so, what years should I look for?

You can tell by looking at the pump if the converter feed has been restricted.

If it were me and I didn't have a lot of experience with TH400s, I think I'd start fresh with a unit needing a refresh. That way you know what you're starting with and you can be reasonably sure it's not been modified. The 'best" years to get, IMO are the 69-70 TH400s. They have the good center support (all 69-later ones do) with the spacer ring, and they have the good direct drum (all 70-earlier do). If you can't find those two years, no worries, as you can use a donor trans or do or the aftermarket to get those "good" parts. Even if you can only find a long tail unit in those years from a full size, you can still use your old trans to swap it into a short tail.

Plan on getting everything to do a complete rebuild....frictions, steels, gasket set, bushings, torrington bearings and a shift kit. It's no secret that Transgo has the best shift kits. There are a couple of additional upgrades that are worthwhile and won't set you back much. I can share some websites with you that I've found that have good inexpensive 400 parts if need be.