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'76 280s a/t sudden no shift.

Started by nik97, 18 January 2010, 02:07 PM

nik97

Hello all.  I am new to this site and I am posting for my father who owns a beautiful '76 280s.  I ran a search using 'transmission' and did find some relevant info however, more would be very helpful.

Here's the situation; basically the car starts and runs fine but recently the trans will not shift out of park.  The shifter moves freely and the linkage appears to be ok(inspected underneath). When shifted from 'P' to any range nothing happens but park works mechanically(driveshaft locks).

This problem was not a gradual failure; the car was parked for a few days and failed to go into gear next time it was started. 

Here are a few conditions with the sudden failure that may be helpful in trouble shooting: The dipstick, which read normal before now reads about 2" above the max indicator mark. Now I'm no automatic trans specialist but that tells me that fluid is not being pumped into the valve body, converter and various circuits of the trans...  :-[  My best guess from a distance would be that there is a failure in the pump itself or perhaps there is a pressure regulator(check ball/spring) that has failed allowing fluid to be simply redirected into the pan... I'm not sure.

Also, the car did have the torque converter replaced withing the last couple years.  My father did his best to explain what had gone wrong to me.  Apparently, some section of the converter drives the input shaft and possibly fluid pump and an 'ear' had broken off creating poor performance and a horrid noise.  This may not be relevant but I thought I'd mention it because the failure areas are proximal.

Anyway, any info is helpful and appreciated.  Surely this is not the first time this has happened so maybe I'll get lucky ;)
Thanks in advance.

Big_Richard

2" above max even without the engine running, ie, no pumping of fluid and a drained torque converter sounds like over filling to me.

from memory its the ears on the torque converter that slot into the central gear of the front pump, the torque converter is bolted via a flex plate to the fly wheel. if these have snapped off again, there will be no pumping what so ever.

It sounds like that transmission requires removal for inspection regardless.

nik97

Quote from: Major Tom on 18 January 2010, 06:05 PM
2" above max even without the engine running, ie, no pumping of fluid and a drained torque converter sounds like over filling to me.

from memory its the ears on the torque converter that slot into the central gear of the front pump, the torque converter is bolted via a flex plate to the fly wheel. if these have snapped off again, there will be no pumping what so ever.

It sounds like that transmission requires removal for inspection regardless.

Yeah that's true. It was at the proper level before the failure and it's 2" above max when running now. 

I had wondered if the previous converter failure had maybe fractured or damaged a part of the pump that just took some time to fail completely.

Thanks for the reply.

WGB

Does the parking pawl actually  release when shifted out of park - may be jammed or rusted in place.

Seems strange that the drive to the oil pump should shear off when parked - I did one years ago in a 5 litre V8 Commodore with the "traumatic" gearbox - but that sheared during a maximum rev change from first to second.

I guess something could have rusted while parked and allowed the pump to shear.

Anyway it needs an expert for the diagnosis - at least one with a transmission oil pressure gauge.

Bill