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Re: What typically fails in the automatic, long reply Posted by Cmyles [Email]  (#1126) [Profile/Gallery]
(more from Cmyles) on Wed, 8 Sep 2010 20:02:54
In Reply to: What typically fails in the automatic transmission? nm, BAAB   [Profile/Gallery]
, Wed, 8 Sep 2010 13:55:34
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BAAB,
Well lets' see... (engage memory)...use and abuse will generally dictate the nature of which components go first. Well maintained units with about 150,000 miles on them will, first and foremost, typically have a burned up forward drum clutch pack. The flex band for second gear will usually need replacing and the rear drum may have clutch pack damage and be scored on it's circumference from the worn band. It isn't unusual to see damage to the forward clutch drum and/or hub, the front housing input shaft bore and the accumulator seals. The unit also has a number of flat Torrington thrust bearings which sometimes begin to decompose due to compromised lubrication and/or overheating. Any deterioration of these parts will free small, nasty particles into the circulating ATF which may jam the valves in the valve body and the governor. Of course in such a well used unit you can find almost any parts damaged including the pump gears, servos and servo bores. In a well maintained unit you don't usually see damage to the primary chain drive elements, input shaft, rear sun gear shaft, rear drum (apart from possible external scoring which can usually be machined away), rear band, plumbing (tubes), valve body, governor or planetary gear assembly and output gear (unless the shift control mechanism had been mis-adjusted). The torque converter is fairly reliable but can't really be cleaned out (remember the circulating swag) so it's best to install a rebuilt one. It's important to scrupulously clean out the cooler and it's circuit (think swag) or get used to doing that R & R. I saw some of these units that had circulated large amounts of finely ground metal from needle bearings and other sources. Nearly every bore and valve that moves in them would have severe, irreparable damage sufficient to preclude smooth (or even any) motion of the valves. Cost effective rebuilding of these guys used to (in the 1990s) mean having a lot of cores to get pieces from. Back then I could usually make one really good unit from two or three worn out ones. Those were nearly all virgins (not previously rebuilt) but today I'd be surprised to see such an animal on the bench so that ratio is probably at least 4:1 or 5:1 now (or worse). Having a machine shop at your disposal is almost essential as well. And just for context, I thought these were pretty good transmissions.
posted by 198.233....
, Wed, 8 Sep 2010 13:55:34, Wed, 8 Sep 2010 20:02:54 <-- Viewing This Message
, Thu, 9 Sep 2010 10:14:11, Thu, 9 Sep 2010 08:43:41
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