I have a turbo 350 in my 67 Firebird and It shifts to soon. If I put it in drive and take off hard from a dead stop it shifts around 3000 RPM or so I would like it to shift closer to 4500 RPM . where do I start. do I need to adjust the modulator? governor? Kickdown or a combinnation of these? where would be the first place to try? 2nd? etc. I had a TH350 in my 67 chevy II that shifted around 5500 RPM and that was perfect for that combination but it has been a while and I have forgotten what I did to get it there.
They are all interrelated. Make sure its all in good condition first. Then I would adjust your Governor, because it controls your WOT shifts. Mr gasket makes a governor weight kit and there are others too. Look for the posts on the board, lots of good info. good luck
Yep, Start with the GOV as it controls the shifts at WOT. Though fiddling with the modulator for low speed part throttle shifts is worth while too if you drive street allot. I can just touch the gas lightly and leave most traffic without trying with higher part throttle shift points. Sounds like a riddle but I enjoyed the change.
Thanks, I will check into the kit. The trans is brand new, just a few hundred miles at best. I am sure this will help. Thanks! Chris
Make sure your downshift cable is connected and adjusted. Then modify the governor with this kit. Change one weight at a time, and then roadtest. http://www.jegs.com/i/B&M/130/20248/10002/-1
yeah the kickdown is set correctly, I did that first. I was kind of thinking I needed to get into the govenor next but wasn't sure. what does the modulator control? Chris
The modulator opposes governor pressure in the trans via spring pressure, modified by engine vacuum. It modifies part throttle shift points based on engine load as determined by the vacuum. I think.....
Modulator tells the valve body what the engine load is. Engine vacuum is a good indicator of engine load. The governor gives the valve body a road speed signal. The downshift cable tells the valve body throttle position. The valve body gets these inputs and comes up with shift points depending on those inputs. Adjusting the modulator only affects minimum throttle shift points. The range of adjustment is only 2-4 MPH. The Governor is what you must play with for your full throttle shift points, the modulator will do you no good.
I agree that governor is the controller of the shift points, but isn't it possible to find a shift kit that changes the 1-2, 2-3 shift valve springs in the valve body (or even the orifices from the governor to the shift valves) to adjust shift points as needed? Is the governor on the th350s is easily removed like the 400s? Been along time since being around a 350 turbo.:blast:
I got more then 2-4mph out of my adjustable modulator, and I didn't go past 1-12 turns, which way I forget Same results both before and after the new trans as I used the same modulator. Just had installed it in the old one. Though yes the GOV controls the WOT shift points.
Be careful. It is possible to lower modulator pressure to the point where the line pressure gets low, and then the transmission can slip under certain conditions.
I don't know if that is possible, but why would you want to remove the valve body when it's easy to access the governor and modify the weights. The kit makes it easy.
I used the governor Kit (B&M) part number 20248 from (I can't remember which one) either Jegg's/Summit (they both sell them) to change the shift points for my 350 turbo transmission. My transmission now shifts about 5300-5400 RPM under WOT every time. I used the # 3 and # 4 weights and the yellow/blue springs. Yours might not shift as mine does but some trial/error will give you the results you want. Good luck.
I went from a quick shift into 3rd before 20 to now 1-2 happens at 20MPH 2-3 happens at 35MPH. Now if I granny it, it will shift sooner but a normal light take off from a stoplight is allot better now as it hold frist a good 10MPH more. I can leave traffic from a light without needign to try or look like Im trying and get away from folks. Before and after an adjustable mod with either old or new trans was like that, I also end up opening all 4 less often.
Just mentioned it, since a shift kit might want to be installed to modify line pressure for harder shifts, etc. The governor kit makes it simple if the governor is indeed accessible without removing the extension housing, and it probably is on TH350!p
