‘78 was the mid year change over from non-lock up to lock-up.
About 6 months of big blocks got lockup transmissions, before the big blocks went bye bye.
Changing differential gear ratio will have no effect on lock-up - except it will come on at a different MPH (based off of the difference in gear ratio you are currently using). Lockup comes on when coasting or low power, so gear ratio and tire size will not effect lockup operation.
Also the shift points will be different with tire size/gear ratio changes as well - but to transmission, it is acting the same as it always did (transmission doesn’t see tire size or gear ratio). It only hums along at a higher (or lower) engine speed based off of what MPH you are driving.
Installing any kind of shift improvement kit on a worn transmission generally causes more problems than fixing. If you have transmission problems, get that fixed first.
A automatic transmission is a hydraulic computer. There are several kinds if shift improvement kits out there, each one is programming the transmission in a different fashion. Some are good improvements and some are not so. The factory worked hard to make transmissions last past warrantee, for smooth shifts (and better fuel economy?) and seldom for performance.
There is several tug-of-wars going on inside and most shift kits alter such by one or two methods. Increasing line pressure is one method. Changing governor weights/springs, is another method. As well as changing clutch pack springs, changing accumulator springs, and so forth. Changing any one item can/will effect the operation of the other items. The worst thing you can do is make two opposing clutches engaged at same time (think applying gas and brake at same time) or having a clutch apply late (like holding clutch petal down and gas petal down after shifting to next higher gear).
Listen to your transmission shop. He has to stand behind his work and he will know what is good (or bad) for your transmission.
The good thing about todays electronic transmissions is they are easier to program (and not so messy).
I can tell you exactly what a 904, 998, 999, 727, 518, 500, 604, etc. transmissions are doing at pretty much any time, and have been inside many hundreds of them.
Note: the automatic shift kit I prefer to use . . . is manual transmission.
About 6 months of big blocks got lockup transmissions, before the big blocks went bye bye.
Changing differential gear ratio will have no effect on lock-up - except it will come on at a different MPH (based off of the difference in gear ratio you are currently using). Lockup comes on when coasting or low power, so gear ratio and tire size will not effect lockup operation.
Also the shift points will be different with tire size/gear ratio changes as well - but to transmission, it is acting the same as it always did (transmission doesn’t see tire size or gear ratio). It only hums along at a higher (or lower) engine speed based off of what MPH you are driving.
Installing any kind of shift improvement kit on a worn transmission generally causes more problems than fixing. If you have transmission problems, get that fixed first.
A automatic transmission is a hydraulic computer. There are several kinds if shift improvement kits out there, each one is programming the transmission in a different fashion. Some are good improvements and some are not so. The factory worked hard to make transmissions last past warrantee, for smooth shifts (and better fuel economy?) and seldom for performance.
There is several tug-of-wars going on inside and most shift kits alter such by one or two methods. Increasing line pressure is one method. Changing governor weights/springs, is another method. As well as changing clutch pack springs, changing accumulator springs, and so forth. Changing any one item can/will effect the operation of the other items. The worst thing you can do is make two opposing clutches engaged at same time (think applying gas and brake at same time) or having a clutch apply late (like holding clutch petal down and gas petal down after shifting to next higher gear).
Listen to your transmission shop. He has to stand behind his work and he will know what is good (or bad) for your transmission.
The good thing about todays electronic transmissions is they are easier to program (and not so messy).
I can tell you exactly what a 904, 998, 999, 727, 518, 500, 604, etc. transmissions are doing at pretty much any time, and have been inside many hundreds of them.
Note: the automatic shift kit I prefer to use . . . is manual transmission.