irratically shifting between gears
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Possible that it is the torque converter locking and unlocking? Can't happen in first. It would happen right at the 1-2 shift and lug down.
Mark E.
TexasT
Texas, Where are you from
- Joined
- Sep 10, 2002
- Messages
- 7,188
Mine does it at around 20mph between 2-3 and around 40mph between 3-4 if I try to stay at those speeds. Not all the time but usually when in traffic. I plan to change the 2-3 shift spring to something a bit stiffer next time I drop the pan. If that works then ill probably do the same for the 3-4 spring.
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Posted from the TurboBuick.Com mobile app
The symptoms describe a shift valve that can not schedule due to a balance issue.There is bias between TV upshift oil (engine load signal) which is used to keep the shift valve closed against governor pressure (vehicle speed signal) that is used to schedule the shift valve, resulting in the valves inability to schedule.It is usually caused by small leaks in the circuits. Something as simple as tightening the TV cable two clicks may correct the problem.If it does not help, retorque the valve body and governor cover and check results. If it does it more on an incline than on a flat surface it points to a leak in the TV upshift circuit. Under what conditions is it more prevalent?
mikestertwo
Well-Known Member
- Joined
- Sep 13, 2006
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- 5,249
What mods were done to the transmission? What I have found is opening the direct clutch feed orifice in the spacer plate causes this issue. If you dual feed plus open the orifice it aggravates it even more. It's called 2-3 hunting. The pump controls pressure by controlling volume. At light throttle angles the pump volume is relatively low. When the 2-3 shift occurs there is a sudden pressure drop because of the high volume demand from opening the feed orifice and dual feeding which the pump cannot react fast enough to. This causes a down shift into 2nd. After the down shift the pressure rises again and the transmission shifts back up to 3rd gear. Then the cycle starts all over again. Accelerating increases the pump pressure so you have more oil volume and the problem disappears. This is why all the tranmissions I build I leave that direct clutch orifice alone. GM uses that orifice size to control the flow rate to the clutch. If that flow rate is too high at low pump pressures this problem will occur. You could have other issues like a leak somewhere like Chris suggested also. This is just the experience I have seen with these transmissions.
Mike,the orificed governor feed oil is a derivative of D4321 oil from the forward clutch. 2-3 oil is from RND4D3 oil. Both are directly supplied from the manual valve and will see minimal interruptions in pressure and volume loss even when the system takes a gulp .This is because of their close and immediate proximity to the oil source. This eliminates step downs in the system which result in volume losses. moving the selector lever from Park to D4 or any other drive range requires the manual valve opening the reverse passage to charge and then to exhaust in a split second. This actually leaves residual oil in the direct passage for the 2-3 shift.The dual feed methods, if done with a particular seperator plate, will actually allow the direct clutch to exhaust apply pressure but allow the circuit to be partially full of oil, reducing purge requirements during 2/3 upshift even with the added capacity required to apply the piston. I have seen shuttling, but most of it is incompatible governor and valve body combinations, as well as low TV limit pressure resulting from worn valve, valve bore and or spring.
