TH400 Governor Modification for WOT shifting

[Supercharged111]

If only I could remember non-car stuff this well.

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But I can't see crap in that pic, will need to get something better focused. Don't worry, that zip tie among many other atrocities have been rectified since the pic was taken.

 

[Supercharged111]

Alright this thing has me at wits end. I got ahold of a bunch of weights from a Superior shift kit and thought I'd be all set. Threw in a set of B weights, second heaviest they make and car logged a max of 4240 RPM. Sweet, my new baseline is 110 RPM in the right direction! So I swapped one of the weights for a C (lighter) and saw 4250. Strange, I expected more. In went the other C weight and swapped the heavy spring for a slightly less heavy spring. 3650. WTF?! In went the D weights and stock springs. 3850. Are you f'ing kidding me right now? So I'm royally p!ss3d off at this thing. I figured if I kept going eventually I'd see it go in the right direction and not the wrong one! How in God's name can this thing shift later with heavier weights?! The valve floats freely inside the bore and the kickdown is still working.

 

[L31MaxExpress]

Alright this thing has me at wits end. I got ahold of a bunch of weights from a Superior shift kit and thought I'd be all set. Threw in a set of B weights, second heaviest they make and car logged a max of 4240 RPM. Sweet, my new baseline is 110 RPM in the right direction! So I swapped one of the weights for a C (lighter) and saw 4250. Strange, I expected more. In went the other C weight and swapped the heavy spring for a slightly less heavy spring. 3650. WTF?! In went the D weights and stock springs. 3850. Are you f'ing kidding me right now? So I'm royally p!ss3d off at this thing. I figured if I kept going eventually I'd see it go in the right direction and not the wrong one! How in God's name can this thing shift later with heavier weights?! The valve floats freely inside the bore and the kickdown is still working.

Lighter springs tend to stack the shifts.

 

[Supercharged111]

Lighter springs tend to stack the shifts.

What exactly does that mean? I was reading in the B&M guide that lighter springs produce later shifts, but spread the shifts apart? After my last rant I caved and swapped the heavier of the factory springs for a red spring from the Superior kit to go with the D weights and light factory spring.

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I wish I could call that run a success, but the reality is that it ran out of fuel and I lifted there. I only hit that once, but I don't think it was done yet. I guess I need a pump and/or high flow needle and seat? Kinda stuck here for the time being until the car can make a clean pull. It acted a lot different. Part throttle shifts were noticeably delayed, too much really. But that was the first change that did anything all day. When I got back home I put all but the D weights on the scale. In terms of overall mass, the C weights are the same as the stock weights, but the nose appears to have less mass.

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From left to right stock, B, C. D looks just like stock but is thinner. My guess is if it's not right for me, E is. But first I need Fast to expand upon what stacked shifts are.

 

[NickTransmissions]

What exactly does that mean? I was reading in the B&M guide that lighter springs produce later shifts, but spread the shifts apart? After my last rant I caved and swapped the heavier of the factory springs for a red spring from the Superior kit to go with the D weights and light factory spring.

But first I need Fast to expand upon what stacked shifts are.

Stack shifting is a term that's used to describe shifts that occur in rapid-fire succession, one shift immediately after the other without any time in between to remain in gear so the engine can build power. In other words, the shifts are stacked right on top of each other...

I can't make out the first letter in that picture of the ID tag so if you know what it is, post it but per my list, assuming it's a chevy case, its likely to be from one of the below applications:

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If 'FI' are the two letters on the left, then you have a TH475 from the 80s...

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As far as the governor set up goes, start with the lighter, inner weight 'C' and keep the same outer weights and springs that were on it originally then go from there. Don't try to change everything at once; sometimes it takes a few iterations to get it right. Here's an article that seems to cover TH400 adjustments in a car somewhat similar to yours, in case you haven't seen it....You also may need to adjust / upgrade your carb as you mentioned...

I don't watch any threads I post in so if you would like me to reply back, please quote my post-TIA.

Hope you can get it worked out...

 

[L31MaxExpress]

Sorry for the late reply. The lighter springs stack the shifts because they go into coil bind and thus become solid more quickly. Find a factory high rpm governor like a 85-93 Corvette or 1980s 2.8L S10 unit and use the outer weights from it. I had better results keeping stiffer springs and using lighter weights. In my case going from memory here, the springs had very little effect on the 2-3 shift but more of an effect on 1-2. I got it to shift 2-3 where I wanted using weights alone, then played with the springs a bit to get 1-2 close to where I wanted it. I also used a Red stripe aftermarket adjustable modulator. You can tighten the modulator set screw a bit to raise all the shift points. The modulator has more effect on part-throttle but it also has some effect on WOT as well. Never understood why given I had a functioning kickdown solenoid. You can modify the valve body for manual gear selection if you want as well although probably a bit dangerous to the engine if you have a column shift. Its easy to accidentally select 1st instead of 3rd at high speed and if you have it moded it will shift to 1st at 90 mph.

I have always found it hard to get consistent 1-2 and 2-3 shift points. This 700r4 would shift 1-2 @ 5,250 and 2-3 @ 5,500. I am sure I could have messed with it more but it took some time getting it there and drove well so I left it alone.

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[Supercharged111]

Stack shifting is a term that's used to describe shifts that occur in rapid-fire succession, one shift immediately after the other without any time in between to remain in gear so the engine can build power. In other words, the shifts are stacked right on top of each other...

I can't make out the first letter in that picture of the ID tag so if you know what it is, post it but per my list, assuming it's a chevy case, its likely to be from one of the below applications:

You must be registered for see images attach

As far as the governor set up goes, start with the lighter, inner weight 'C' and keep the same outer weights and springs that were on it originally then go from there. Don't try to change everything at once; sometimes it takes a few iterations to get it right. Here's an article that seems to cover TH400 adjustments in a car somewhat similar to yours, in case you haven't seen it....You also may need to adjust / upgrade your carb as you mentioned...

I don't watch any threads I post in so if you would like me to reply back, please quote my post-TIA.

Hope you can get it worked out...

That article sort of tracks with my observations. I figured those really light weights were needed for 7000 RPM shifts, not 5200. Next time I'm out there I can snag a pair of E and F weights to try with the factory springs. I'll be watching fuel pressure through a pull as well. This whole thing is aimed at dialing in the carb, though the carb seems to be working quite well as is. Kinda tough to tune for an RPM range you can't even touch though.

 

[Supercharged111]

Sorry for the late reply. The lighter springs stack the shifts because they go into coil bind and thus become solid more quickly. Find a factory high rpm governor like a 85-93 Corvette or 1980s 2.8L S10 unit and use the outer weights from it. I had better results keeping stiffer springs and using lighter weights. In my case going from memory here, the springs had very little effect on the 2-3 shift but more of an effect on 1-2. I got it to shift 2-3 where I wanted using weights alone, then played with the springs a bit to get 1-2 close to where I wanted it. I also used a Red stripe aftermarket adjustable modulator. You can tighten the modulator set screw a bit to raise all the shift points. The modulator has more effect on part-throttle but it also has some effect on WOT as well. Never understood why given I had a functioning kickdown solenoid. You can modify the valve body for manual gear selection if you want as well although probably a bit dangerous to the engine if you have a column shift. Its easy to accidentally select 1st instead of 3rd at high speed and if you have it moded it will shift to 1st at 90 mph.

So it sounds like the reason I find myself on the extreme end of these inner weights is because this thing has heavier outer weights than some of the other vehicles? That would make more sense. Setting that 2-3 is going to be pretty sporty, with the 2.73 rear end and 27" tires (assuming no torque converter slip) that puts me at 100mph. I'd only been watching the 1-2, maybe the 2-3 is already up there then and the spring change got the 1-2 where it ought to be? Time to fix that fuel issue I guess. I have an adjustable modulator, but it's just gold in color. I've heard of the red stripe before, I'm guessing it has a stripe in the color red on it somewhere.

 

[L31MaxExpress]

So it sounds like the reason I find myself on the extreme end of these inner weights is because this thing has heavier outer weights than some of the other vehicles? That would make more sense. Setting that 2-3 is going to be pretty sporty, with the 2.73 rear end and 27" tires (assuming no torque converter slip) that puts me at 100mph. I'd only been watching the 1-2, maybe the 2-3 is already up there then and the spring change got the 1-2 where it ought to be? Time to fix that fuel issue I guess. I have an adjustable modulator, but it's just gold in color. I've heard of the red stripe before, I'm guessing it has a stripe in the color red on it somewhere.

One band of red. Converter is rusty but the TH400 only has 110K on it so I let it be.

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[Supercharged111]

Well well well, lookie there I guess I do have that same modulator.

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It's faint but you can see it. And even though it's gunky and dirty, I don't even think this thing has 100k on it.

It's probably worth mentioning this thing has a ratchet shifter so I'd be safe in modding the trans to do what it's told.