raptere

I had posted this in a thread on my AutoX experience, but I thought this was a topic that people could benefit from and find more easily here in the Transmission section.

I decided to grab a trans governor re-calibration kit. It was pretty cheap, and I wanted to increase my shift points a bit. This plays to the power curve of my stealth ram, and once I pull the trigger on the higher stall torque converter, it will give me more usable RPM range. I kind of went down the rabbit hole on this topic, since there are so many anecdotal posts, but very little numerical data. I ended up getting the Superior kit, since it supposedly had better C clips, and was about half the price of the B&M and TCI versions. They're all basically the same thing.

PSA: I have heard of a lot of varying stories about how much oil comes out each time you pull the governor. I found that the way I lifted the car up, using my ramps in the front and jack stands in the back so that the back was still somewhat higher than the front, only maybe an ounce of oil dribbles out each time. Maybe less! Sounds like level or worse yet, the front end up high and the rear on the ground, people have been losing upwards of a full quart.

I would be interested in peoples opinions about how far it is safe or logical to go with shift point for my setup??? I was thinking 5400-5500 rpm? As the charts say stock was about 5k. Factory '91 Z28 350 with stealth ram, 1.6 roller rockers, ignition box and upgraded coil, and full exhaust, if it makes a difference a 3.23 posi 10 bolt rear...

First, I took detailed measurements of the weights, they seemed to have two different thicknesses some of which shared general profile shape:

It seems the positioning of the weight is very critical to the function of the weights. This is why I experimented with my paperclip method. I bent a paperclip to act as pin for the weights to rotate freely on. I set the weight on the scale then with the paper clip lifted the axle side off the scale just slight, and as smoothly as possible and recorded the weigh. Not sure if the value is terribly useful, but it does help account for the shape of the weights and the weight distribution.

And the springs:

I did this at a point when the governor was installed in the car so there were some assumptions made, but the numbers should at least be proportional. I found it very interesting that the order of weight advertised by Superior doesn't seem to match my calculations...

These are the results of my testing so far:

I first tried the D weight in place of the factory weight that was on the light spring side, but while it was lighter, I think there was more weight at a greater radius from the pin, so it actually shifted slightly earlier than stock. I therefore reshaped the same weight to have the same profile as the stock weight, but out of thinner material, this one brought my shifts up 3-400 rpm from the un-modified D weight and up 2-300 rpm from stock. I may try drilling a few more small holes near the end to shave off another about 0.3g. (My calculations estimate a 3/16 hole near the center, and two 1/8" holes on either side of it, should remove the needed 0.3g given the thickness of the D weight.) That will place it halfway between the current weight and the next in line E weight in my Supirior kit.


***Please read the units, since I worked on different parts of this at different times, I admit I jumped around a bit between metric and imperial, sorry...***

Pro Built Automatics

If you want to make a 5,500 rpm setup. Then you need to get a valve body or the shift valves (1-2, 2-3 & 3-4 shift valve) from a Z28 type and the matching Z28 governor. You can get it somewhat close doing it you way. However, you will not get all three shifts to be even close to being the same at WOT.
If you have access to a few valve bodies. Then I can give you the needed information as to what to look for on the valve body. The Z28 governor is easy, and you already have the governor spring and weight kit. So you can make that yourself. If you are interested. I will post the information needed.

raptere

Hey Pro Built, I actually got your 700R4 TransGo Street/Strip Shift Kit 1988-1993 w/Accumulator Pistons w/Seals, pins, Corvette Servo & pre-drilled separator plate, and installed it last year. Does that make any difference to your comments above?

Also, I'm a little confused why you're saying I need parts from a Z28 trans to make this work. I have a 1991 Z28. I was under the impression the trans I have is about as good of a starting point as you can get for a thirdgen... The governor is the same one with the large window in the heavy weights as I though was what came in the Corvettes of similar years.

At this point I really do not want to have to drop my valve body again, so I'll probably just keep inching my way up to see how close I can get. An extra 500 rpm seems like a pretty small ask from changing governor weights/springs... I'm still trying to nail down if 5500 rpm is the right shift point for my set up too, but it seemed like a good place to start, without getting myself in too much trouble, considering some cars were made that way from the factrory.

Pro Built Automatics

Did your governor have the outer weight with a large round hole? Or the one with the skeleton type outer weight?

raptere

Skeleton type. The photos above are of my actual factory governor.

Pro Built Automatics

What are the letter or number codes on the 1-2? 2-3? 3-4? shift valve bushings? The 1-2 is on the outside edge of the valve body. The 2-3 shift valve bushing is next, and the 3-4 is the one in the middle of the valve body.
If the number/letter code on the shift valve bushing are correct. Then you have the 5,500 rpm WOT setup. Are you wanting a higher than 5,500 rpm WOT shift?

raptere

Are these markings inside the valve body or outside? I took a decent number of pictures during the process, but these are probably the best two. Are you able to see what you need to see here? I did check before adding your shift kit, and my car was shifting right around 5k, so I think that is where it was supposed to be. If I in fact have a 5000 wot setup, would you thinking tweaking the governor weights and or springs, could get me to about 5500? I think that is all I'm looking for.

Pro Built Automatics

The front of the valve body, facing the motor. There will be the aluminum bushings with the letter/number code I mentioned.

raptere

These seem to be the only two pictures I have of the front of the valve body, but I'm not seeing any identifying markings, are you?


Sorry this one is out of focus...

raptere

10-8-23 UPDATE: Swapping the E weight for my modified one, got me to ~5400 RPM WOT 1-2 shift. This is about what I was looking for! Other springs and weights left the same. This was done at the same time as I swapped in my 2600 stall converter, but I don't think that should have an effect on WOT shifts...