Shift Kit Effects on TH350, Need Guidance

[G_RIDE_81]

Hope all is well, G Body peeps!! I'll get straight into it.

1981 Chevy MC, stock rebuild 350ci, basic rebuild TH350 with shift kit, 3.42 posi. Everything else is pretty much stock. The posi was recently added after my original rear end crapped out. The new deeper 3.42 gears has obviously raised the RPM’s at higher speeds. No surprise there (I hope to get a 4 speed auto soon). What I wasn’t expecting was that my 1-2 and 2-3 shifts are coming in sooner, 13 and 20 mph respectively if I’m reading speedo correctly. I adjusted the modulator screw to its most inward setting, raising the shift points maybe 2 mph each. Still seems too early from what I remember the original shift points being. This was not noticeable before with my stock rear end.

I’ve done some research for over a week and learned that some shift kits add a spring (not included in stock transmissions) to the modulator valve which both firms and “lowers” shift points. Is this accurate? If so, should removing this spring raise shifts points a few more mph?

I know removing the modulator, with trans in car, will cause a small amount of oil to spill out. Will also removing the valve cause additional amounts of oil to spill or not really?

Any knowledge you can share will be much appreciated. Thanks in advance!

 

[ELCAM]

What engine RPM are the shifts at?

 

[ELCAM]

I am thinking something like this is in order.

B&M 20248: Governor Recalibration Kit GM TH700R4, TH400, and TH350 - JEGS

Reclaibration Kit

www.jegs.com

scroll down to instructions and read that.

From the instructions: "Heavier weights produce earlier shifts, lighter weights produce later shifts. Stiffer springs tend to produce earlier closely stacked shifts, weaker springs tend to raise and spread apart shift points."

You can modify what you have without spending any money.

 

[melloelky]

you don't lose a lot of fluid removing the cover.it's real trial and error.pull yours apart,use their guide to see what's in it now.from there you're changing springs/weights reinstalling it and test driving.more than once..

 

[G_RIDE_81]

I am thinking something like this is in order.

B&M 20248: Governor Recalibration Kit GM TH700R4, TH400, and TH350 - JEGS

Reclaibration Kit

www.jegs.com

scroll down to instructions and read that.

From the instructions: "Heavier weights produce earlier shifts, lighter weights produce later shifts. Stiffer springs tend to produce earlier closely stacked shifts, weaker springs tend to raise and spread apart shift points."

You can modify what you have without spending any money.

ELCAM, thanks for replying.

I don't have a tach but I do have an "engine analyzer tool" that plugs into and read rpm's. Thanks for reminding me,, I need to hook it up and check. Also, I order the Jegs version of the governer recalibration kit, hasn't arrived yet. But I heard that only affects WOT 2-3 shifts...?! My MC is more of a daily cruiser.

 

[G_RIDE_81]

you don't lose a lot of fluid removing the cover.it's real trial and error.pull yours apart,use their guide to see what's in it now.from there you're changing springs/weights reinstalling it and test driving.more than once..

Regarding the governor removal, yes not much fluid. I've seen lots of how to videos on this.

I haven't found a video on modulator valve removal while trans still in the vehicle.

 

[ELCAM]

The smaller inner weights affect the WOT shift points, the bigger outer weights affect 1-2 and part throttle shifts.

So in the kit I posted the weights are going to change the WOT shifts only the kit supplies the small weights you reuse the stock heavy weights. The springs will change the 1-2 and part throttle shifts. If you like the WOT shift point just change the springs.


Edited to add:
Been doing a little looking at the TH350 book.

If the governor and modulator wont play well together there are springs you can change in the valve body. Try everything else first.

 

[ELCAM]

One last thought is a 700R4 governor (fits the TH350) , look for a car with the taller gears like a 6 cylinder camaro. It should have shift points for higher rear axle gears but not crazy high WOT shift points.

 

[G_RIDE_81]

The smaller inner weights affect the WOT shift points, the bigger outer weights affect 1-2 and part throttle shifts.

So in the kit I posted the weights are going to change the WOT shifts only the kit supplies the small weights you reuse the stock heavy weights. The springs will change the 1-2 and part throttle shifts. If you like the WOT shift point just change the springs.


Edited to add:
Been doing a little looking at the TH350 book.

If the governor and modulator wont play well together there are springs you can change in the valve body. Try everything else first.

Noted! Digging into the valve body would be beyond my DIY skills so hope not to go that far.

 

[G_RIDE_81]

One last thought is a 700R4 governor (fits the TH350) , look for a car with the taller gears like a 6 cylinder camaro. It should have shift points for higher rear axle gears but not crazy high WOT shift points.

Makes sense. Will keep this in mind. My calibration kit won't arrive for a few more days. Hope to work on it weekend after this.