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Gary, Chevy Technician
Category: Chevy
Satisfied Customers: 16635
Experience:  15 years GM master tech
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Chevrolet Scotts dale: Trouble with my 84 350 with lock up

Customer Question

Trouble with my 84 350 with lock up transmission works for awhile then feels like it goes into neutral shut truck off goes maybe 50 feet does it again
Submitted: 1 year ago.
Category: Chevy
Expert:  Gary replied 1 year ago.
when this happens it has no drive gears at all ?before you shut it off at a stop will reverse work ?
Customer: replied 1 year ago.
Nothing works until I shut it off and this is second trany other one did same thing
Expert:  Gary replied 1 year ago.
2WD or 4X4 ?
Customer: replied 1 year ago.
2 wd
Expert:  Gary replied 1 year ago.
this is very odd with 2 transmissions doing the same thingas by default there should always be a forward gear no matter what happens with the shift solenoidcan you make sure the fluid is full and if it is before you shut off this truck and its acting up can you see if reverse works and also see if the drive shaft is turning out of the back of the transmission when this is acting up ?
Customer: replied 1 year ago.
Tried un hooking wires changed oil and filter lots of vacuum
Customer: replied 1 year ago.
And lose all gears
Customer: replied 1 year ago.
This one has me beat
Expert:  Gary replied 1 year ago.
if it has no reverse when this happens and the drive shaft is not spinning out of the rear of the transmission when this is acting up there has to be some kind of internal transmission failure going onlike i said by default it should always have a forward gear and reverse no matter whatwhen it does not have reverse and a forward gear it is usually a sign of the forward sprag /one way clutch failure or possibly the pump or converterto narrow this down any more we need to connect a pressure gauge to the test port on the transmission and see what we have for pressure when it will not moveif the pressure is good then it is a forward sprag or converter failure
Expert:  Gary replied 1 year ago.
there are rare times we have seen another used transmission do the same thing
Expert:  Gary replied 1 year ago.
the only other " outside the box " issue that can cause very odd problems like this are a restricted or plugged transmission cooler not allowing the fluid to flow enough and causing a neutral out so to due to low or no line pressureyour best bet is a pressure test and also have the cooler tested for flow before you go through removing the transmission again
Customer: replied 1 year ago.
I have it on jack stands had pressure on lines then lost it when truck warmed up seems weird it's a good tyranny u say maybe torc if it's a none lock up torc would that do it
Customer: replied 1 year ago.
Tran goes directly to rad had rad just cleaned by rad shop
Expert:  Gary replied 1 year ago.
no lock or lock up it should never loose a forward gear and reverseif you see it loosing pressure when acting up then the issue is the pump or a restricted coolerwith a bad sprag or converter it would not loose pressure
Customer: replied 1 year ago.
Seems weird two tranys would do this same thing and this tranny is marked good right on it
Expert:  Gary replied 1 year ago.
i agree with youbut no matter what that transmission is loosing line pressure and it should never loose pressure unless the cooler or the pump is failing if the fluid is filled up
Customer: replied 1 year ago.
Could it be servo if snap ring broke
Expert:  Gary replied 1 year ago.
it still should have forward and reverse
and a servo would not cause the pressure to drop to 0