TH400 Governor Modification for WOT shifting

[Supercharged111]

Has anyone ever monkeyed with their TH400 governor? I need to get this one on my Monte shifting higher WOT, it's not done building steam at 4100. And for some lame reason it ignores attempts to manually shift 1-2 and 2-3. What I'm wondering is where to grind/drill is best, how much, etc. I'm kicking myself as years ago I had a governor kit and sold it cheap. Much cheaper than I can get one now!

 

[Schurkey]

All I can say is to buy another governor kit. TH350, TH400, and TH700 all take the same kit.

You could manually drill weights to change shift points, but I have no idea "how much" to drill. There's inner weights and outer weights.

 

[NickTransmissions]

Has anyone ever monkeyed with their TH400 governor? I need to get this one on my Monte shifting higher WOT, it's not done building steam at 4100. And for some lame reason it ignores attempts to manually shift 1-2 and 2-3. What I'm wondering is where to grind/drill is best, how much, etc. I'm kicking myself as years ago I had a governor kit and sold it cheap. Much cheaper than I can get one now!

Grinding/drilling the secondary, inner weights (or swapping them for lighter weights) is how you increase the shift points at WOT but you may still need some diff springs for fine tuning (won't know until you get done grinding). The outer weights primarily control the timing of part-throttle shifts.

Grinding / drilling is trial and error, not an exact science and you can take off 'too much' if you get overzealous. Alternatively you can see if you can find a Corvette governor in a junkyard and swap the 700R4 gear for the TH400 gear and grind off the 700R4's thrust nipple to set governor end play (travel back and forth within the bore). You could always do two .125 holes in each of the secondary weights to see what impact that has and go from there...

Pics for reference:
TH400

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700R4 Corvette Gov

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A governor kit on Amazon - if purchased, you'd use the small triangular weights in place of the current weights.

 

[L31MaxExpress]

First make sure the kickdown solenoid is good and getting power at WOT. Most TH400s shift in the 4,500-5,000 rpm range out of the box with power connected to a properly functioning kickdown solenoid. The kickdown solenoid raises the detent pressure which operates on the opposite side of the shift valves as the governor pressure.

 

[Supercharged111]

A thought occurs to me, the stock inner weights should be stamped with their weight, right? I'm thinking this motor wants to shift closer to 5000 RPM based on the feel. It's a GenVI Goodwrench bottom end, GenV heads, and MarkIV 4bbl intake with 800cfm qjet. A governor kit isn't out of the question by any means, but I know for a fact I can move in the right direction by drilling a couple holes. I can try a total of 4 .125" holes and see what that nets me if we think it's probably not going to push me north of 5000. Or I could do 1 weight first and see what happens.

And the solenoid was powered, clicking, and made a noticeable difference in trans behavior. I was upshifting at 3000 WOT before I hooked it to a momentary switch as a proof of concept, so next step is also to get a micro switch rigged to the carb so that works properly.

This engine and trans came from a motorhome and the rear end in this car is an aftermarket 9" with an unknown ratio so I'm ASSuming here that the change in ratios is why it's shifting as early as it is. I only just got the Speedo working and have yet to calibrate the thing. Lots more stuff to work through, but with it shifting so early gonna be impossible to get a feel for where the carb is and needs to be. I'll try some 1/8 holes l, see where that gets me, and chime back in.

 

[NickTransmissions]

A thought occurs to me, the stock inner weights should be stamped with their weight, right? I'm thinking this motor wants to shift closer to 5000 RPM based on the feel. It's a GenVI Goodwrench bottom end, GenV heads, and MarkIV 4bbl intake with 800cfm qjet. A governor kit isn't out of the question by any means, but I know for a fact I can move in the right direction by drilling a couple holes. I can try a total of 4 .125" holes and see what that nets me if we think it's probably not going to push me north of 5000. Or I could do 1 weight first and see what happens.

And the solenoid was powered, clicking, and made a noticeable difference in trans behavior. I was upshifting at 3000 WOT before I hooked it to a momentary switch as a proof of concept, so next step is also to get a micro switch rigged to the carb so that works properly.

This engine and trans came from a motorhome and the rear end in this car is an aftermarket 9" with an unknown ratio so I'm ASSuming here that the change in ratios is why it's shifting as early as it is. I only just got the Speedo working and have yet to calibrate the thing. Lots more stuff to work through, but with it shifting so early gonna be impossible to get a feel for where the carb is and needs to be. I'll try some 1/8 holes l, see where that gets me, and chime back in.

I wonder if you have a TH475...if so that would be cool...those were installed in heavy vehicles, including motor homes from 1971+. That gov pic that I captioned "TH400" is actually a TH475 governor as are all the parts in the background (im currently rebuilding it for a chevy truck that i have yet to acquire)...Ill have to compare that governor to my other th400 governors to see if its got different weights/springs designed for earlier shifts...TH475s have 6-clutch direct drums, heat treated stators, 16 element intermediate sprags where most 71+ th400s used those 8-element roller one way clutches which were markedly weaker. The main thing the 475 has going for it is the straight-cut gear sets vs helical style gears in all other 400s, etc.

Post a pic of the ID tag if you can and its still legible...ill let you know if its a 475 or not once i see it...

 

[Supercharged111]

Definitely not a 475, it doesn't howl like straight cut planetaries would. Plus didn't they have drum parking brakes on the output? This one has the 4" tail housing.

 

[L31MaxExpress]

Definitely not a 475, it doesn't howl like straight cut planetaries would. Plus didn't they have drum parking brakes on the output? This one has the 4" tail housing.

Not all of them had drum parking brakes.

 

[Supercharged111]

Tag would have been on one of the 6 tail housing bolts? If so it's gone. If not, please advise where to locate it.

 

[NickTransmissions]

Tag would have been on one of the 6 tail housing bolts? If so it's gone. If not, please advise where to locate it.

Passenger side of the transmission under the two band anchor locations. ****** pic but you can see the small rectangular tag below the two anchor points...

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ETA: Better pic

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