Hello Guys,
I want to disable the forced 1-2 shift on my '86 700r4. From reading thru the posts on this board I learned that all I had to do was remove the MTV spring. I have removed the spring labelled 304 in the drawing below and I still have a forced 1-2 shift. In fact, as far as I can tell, the trans doesn't behave any differently with this spring missing!!! Can one of the trans experts here tell me where I have gone wrong??
Thanks,
Ben.

Yes thats the correct spring. Nice to have these pics floating around lately. Without this spring and assuming the car is locked in 1st gear it should not up shift and I dont know why it would do so unless the valve is stuck in the bore.

Thanks SSC.
I scanned the pic from my ATSG manual. The valve didn't feel sticky in the bore, I slid it back in there no probs at all.
I will leave the spring out for now as long as I cannot damage the trans by driving it with the spring missing.
Does anyone else have any idea why removing this spring did not delete the forced 1-2 shift??
Thanks,
Ben.

What year transmission are we talking about here and what RPM is the forced upshift happening at?

This is weird because every transmission Ive removed the MTV up spring from resulted in no forced upshift excluding one that was rebuilt by a local shop before the MTV springs removal. I know some drilling in the seperator plate like the mentioned truck that the shop had drilled and re routed fluid (thier own shift improvment setup) can make the forced upshift still operate but unfourtunatly thats beyond my understanding of the valve body's hyd routing.

The trans in question was built in '86 and it is in in my 84 vette.
I know the box has been rebuilt, but I don't know by who, or what they may have done to it unfort...
It changes up at about 4900, which is fine most of the time, but when I race it at the strip I wanna push it just a bit harder, and I want to determine when it shifts also!

That sucks! You need a governer calibration kit, if your shifting that early the governer is way out of whack to start. You shouldent be shifting that early even in (od). Forced upshift takes place between 5k-6K factory setup. When line pressure has built up it forces the MTV valve to pop. Removing the spring is supposed to disable this function. I'll dive back into the think tank ans see what else I can come up with.

Thanks for you assistance SSC!
I am reluctant to tamper with the governor as that will alter ALL the shift points won't it?? I am very happy with the way it operates when left in 'D' for 99% of driving, I just want to make it hold 1st if thats where I have the shifter!...
Would a stiffer spring in the MTV raise the rpm at which the forced shift occurs, that way it would require more pressure, and hence more rpm to overcome the spring and force a shift to 2nd... Altho that theory contradicts the idea of removing the spring altogether! Confused ;-(

I don't know what RPM the "forced shift" is supposed to occur at, since rear gear ratios can effect actual RPM, but the speed at which its supposed to happen is 35 MPH.

Installing the TransGo Reprogramming Kit will elminate this forced shift, but I'm sure its not the answer you want to hear. I can tell you the exact mod in the kit that eliminates it, but I have never tried it without installing the rest of the kit, so I don't know if its a good idea or not. Lo-Reverse fluid is directed through the 1-2 shift valvetrain. Lo-Reverse fluid and MTV Upshift fluid act on the valve against governer pressure to keep the 1-2 shift valve in the "downshifted" position, however, at 35 MPH, governer pressure overcomes Lo-Reverse and forces a 1-2 shift. Fluid before the 1-2 shift valve is called "Lo" fluid, and fluid after the valve is called "Lo-1st" fluid. The trick is to drill through a partition in the valvebody combining "Lo" fluid and "Lo-1st" fluid, bypassing the 1-2 shift valve.

I don't have a picture of the valvebody, so I can't show you which partition to drill through, but somebody on here has the instructions to the transgo kit posted, you may want to do a search on it. Its Page 4, Step 1 Since you have an '86 tranny, you want to drill where it says "1st type VB" ONLY! Don't drill where it says "Stick Only" or "2nd type VB".

Thanks GMTech!
I don't mind buying the transgo kit, but it is a bit hard to get here in Australia.
I actually aquired a copy of the Transgo instructions today and was going to attempt to figure which mod deleted the forced shift when I get home from work tonight!
I see the hole that needs to be drilled on page 4 and have circled it in the drawing below! Transgo kit does not even mention the MTV valve or spring, so I suppose I had better pop the spring back in! Thanks!

Do you know what the purpose of plugging hole 'B' on pg3 is?

See, thats just it, thats why I don't like doing just "parts" of the kit. I think you should do it all or none.
However, that hole you are plugging is an exhaust port for the "Lo-Reverse" circuit of the 1-2 shift valve, and since we are bypassing this circuit, then we probably need to block that hole.
Why are these kits hard to get in Australia?

"I don't know what RPM the "forced shift" is supposed to occur at, since rear gear ratios can effect actual RPM, but the speed at which its supposed to happen is 35 MPH. "
How does the tranny know the car is going 35mph?
Mine will 'force' shift at around 6200 or so. I've done it during a burn-out that got a little carried away. But I was going 0 mph at the time. Doesn't the tranny shift based on rpm/throttle position, since that's all it can 'see'? How exactly does rear-end ratio effect 'actual' RPM? I'm asking these questions purely out of curiosity, the quest for a better understanding of transmissions

So what you are saying is, your tranny was slipping 6,200 RPMs. In reality, YOU were doing 0 MPH, but in order for your tires to be "burning out", then they were spinning, which means the output shaft of the tranny was spinning. Had you looked at your speedometer, you would have seen how fast the output shaft was spinning. 6200 RPM in first gear is probably around 35 MPH based on gear ratio. The tranny knows "speed" based on governer pressure, generated by the governer which is driven by the output shaft. During a burnout, the car itself may not be moving, however the driveline is still turning as though you were.

How can gear ratio effect RPM? Speed is calculated by effective driveline ratio (RPM / tranny ratio / rear axle ratio). If you change any of those variable, then the answer to the equation changes. Thats like asking how can a car dive 55 @ 2,000 RPM in third gear, but in 4th gear its doing 70 @ 2,000 RPM. A person with 3.73s is going to turn more RPM's to maintain 35 MPH then somebody with 2.73s.