Our 86 iroc, auto, used to cruise at 65 mph around 2000 rpm. Not its turning 3200 and if i go to 70 mph about 3500 rpm. we didnt make any new changes. the strange part is it's not slipping and i feel it go through all 4 gears plus i feel the tc lockup. to test it, i can start off in 1 gear slowly, the i shift to 2 then 3 then the tc locks up at 40 mph then i put it in 4th. i can also go 60 mph and drop it in 3rd and it downshifts so it does go to 4th. is this a speed sensor problem or what else can it be? STRANGE....

Dora

 

hmmmm. alll i could think of is its not going into over drive... but you say you feel it down shift when you put it into 3rd gear.... could be that your shifter cable is streched and when you put it in over drive it isnt realy going into over drive but actualy just into 3rd gear.... i have had this happen to me before....

put it in OD and then get under the car and make sure the tranny is realy in OD

 

No, driving it up to speed slowly we feel 4 gears and lockup at 40 mph.. thanks.

 

if you downshift into 3rd while going 70 do the rpms shoot up even higher? if so then the tach has gone bad. not too uncommon on these cars.

 

woundnt the rpm shoot up anyway when downshifing to 3rd at 70???

 

yes. if it shoots up higher than the 3500 you mentioned the tach is bad.