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Transmissions and drive-trains Troubleshoot, repair, rebuild.

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Old 01-03-2012, 12:53 AM   #1
Duende
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Default Tranny slipping - '74 Eldorado w/500ci

Having difficulty getting into gear. Requires a lot of revving. Also seems to slip out've gear on the highway occasionally, stumble, recover. Going through fluid fast.

Two day old car. LOL. DD. Oh shit. Any help/suggestions appreciated. 80k miles on the car, haven't ran the VIN through Carfax.
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Old 01-03-2012, 02:54 PM   #2
Schurkey
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Quote:
Originally Posted by Duende View Post
Having difficulty getting into gear. Requires a lot of revving. Also seems to slip out've gear on the highway occasionally, stumble, recover.
  • Low fluid level
  • Plugged filter
  • Leaking filter-to-case seal


Quote:
Originally Posted by Duende View Post
Going through fluid fast.
No visible leaks? Transmission modulator has ruptured diaphragm. Common as dirt.

Visible leakage? Follow the leak source, or
  • Pan gasket
  • Dipstick tube seal
  • Cracked dipstick tube at o-ring "groove" especially if the bracket has broken off the dipstick tube so it's not secured near the upper end
  • Shift-shaft seal, often with a groove worn into the shift shaft
  • Trans modulator O-ring
  • Output shaft (tailshaft) seal and/or tailshaft bushing
  • Torque converter/front pump seal
  • Loose front pump bolts, blows fluid out vent tube
  • Plugged vent




FIX THIS or you're going to burn up that transmission.

Last edited by Schurkey; 01-03-2012 at 02:58 PM.
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Old 01-03-2012, 03:23 PM   #3
Duende
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It's parked until a dry day and your post is printed out. Thank you, sir. :mrgreen:

Worst case, what's a new tranny involve with these things? Any easy source vehicles, huge PITA, anything?

Thanks for your in-depth reply above - really, really appreciated.

All the best to you and yours this new year.
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Old 01-03-2012, 03:48 PM   #4
Schurkey
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Originally Posted by Duende View Post
It's parked until a dry day and your post is printed out. Thank you, sir. :mrgreen:

Worst case, what's a new tranny involve with these things? Any easy source vehicles, huge PITA, anything?

Thanks for your in-depth reply above - really, really appreciated.

All the best to you and yours this new year.
New trans will be a fairly major project. I think the engine has to come out to get the trans out...but I'm not certain.

The trans itself is reasonably easy to work on, it's essentially a common TH 400 that's been split 'n' twisted. Some of the internal parts spin the opposite direction than they would in the 400; and the whole chain drive wouldn't be used on the 400; but the transmissions are strongly related.

There's plenty of 'em out there. Dirt cheap or extravagent, depending on the seller. '67 Eldorado uses a special--different--case, othewise any '66 to '78 Olds Toronado or '68--'78 ElDorado is a donor vehicle. '66 and '67 have a fancy torque converter that changes it's stall speed. Very useful, not near as common.
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Old 01-06-2012, 09:00 PM   #5
Bruce Roe
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Default TH425 Trans

It is generally possible to pull that trans from the bottom while
supporting the top, haven't done that model. I'd like to pull the
trans & final drive together from the bottom, about 400 lb using
special supports. The engine will have to move forward/trans
back an inch to clear the bell housing, and that will only be
possible after the cross over shaft is pulled.

Any original trans that old needs all new soft parts regardless
of miles. The rubber seal on a clutch pack piston seal could be
hard as a rock by now. Once leaking, clutches can slip, it could
burn up and poison the whole trans. Pull that thing and go through
it, before serious damage is done. The hard parts might be fine
at this mileage, a 400 seal kit under $50 will fix most of the rest.
good luck,
Bruce Roe
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