T-400—Partial Rebuild: Waste of time? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 02-10-2009, 02:46 PM
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T-400—Partial Rebuild: Waste of time?

I have a TH400 in a Jaguar that recently failed on me. The vehicle (and the trans) only have 74,000 original miles on them, so I was considering the possibility that a partial rebuild might get it back on the road (under the assumption that most of the components within the trans should still be in decent shape, being relatively low mileage).

The problem with the trans is as follows: Less than a week after getting the vehicle back on the road (within 3 days or so; the vehicle had essentially been sitting for the past 5 years with very little use) the transmission began showing signs of trouble. Though the transmission shifted and operated perfectly for a couple of days, by day 3 it began stalling the engine out intermittently. Next, it began having trouble engaging into 1st after starting the car, and wouldn't engage until the car had warmed up. After a day or two of this, it then would not engage into first when taking off unless the engine was revved to approx. 2k rpms (in addition to being warmed up), and by the next day, would not engage until being revved to 3k+ rpms. By day 5, the trans would not propel the vehicle forward at all. Reverse still works fine, and I should also note that before being put into storage, the transmission never malfunctioned.

I called a local transmission rebuilder, and asked him what he thought the issue might be. He indicated it was probably internal seals that had failed, especially since the car had been sitting for so long. My question is—what internal seals might cause a problem like this? If it is, for example, the valve body, servo, or some other component that could be removed without even dropping the trans, would it be worth it to have just that component rebuilt/replaced? I unfortunately do not have the time or money to invest in a complete overhaul of the transmission, however my concern is whether or not a problem like this could be diagnosed with enough certainty that it would be worth taking the risk of investing in a partial rebuild. (Would a trans rebuilder even take on a job like rebuilding only the valve body?)

That said, my primary goal is to get the transmission roadworthy as quickly as possible, as this vehicle was to be my daily driver while I rebuild the engine on my old Chieftain. Any tips or insights would be greatly appreciated.
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Old 02-10-2009, 02:53 PM
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Would U tell the doctor to "Partialy" rebuild your heart.
Come on now!!!!
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Old 02-10-2009, 03:01 PM
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da34guy, thanks for the response, but that wasn't exactly what I was looking for. A full rebuild is $1500, and times are tough.
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Old 02-10-2009, 03:12 PM
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Quote:
Originally Posted by mrwumper
da34guy, thanks for the response, but that wasn't exactly what I was looking for. A full rebuild is $1500, and times are tough.
Yer gettin bent over for 1500
I get 350's 400's done for 450 on the bench.
Oh yeah yer in California, the land of the strokes
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Old 02-10-2009, 03:48 PM
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I agree, your getting hosed. $1500, my God you can buy a performance rebuilt 400 for that. Check this site, scroll down to the bottom.

Vince
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Old 02-10-2009, 03:50 PM
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$97.95 for a kit. http://cgi.ebay.com/ws/eBayISAPI.dll...03&refid=store
I'd rebuild the whole thing not try to halfdo it.
Shane
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Old 02-10-2009, 03:57 PM
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Sadly, I can't even get a salvaged trans for less than $800 around here (the Jaguar doesn't use the standard GM bellhousing/bolt pattern, unfortunately). On another note, would a doctor insist that a patient with a bad heart receive a heart transplant, if they were convinced that a simple bypass would cure their ailment? When my engine just needs a head job, I don't rebuild the entire short block. Then again, from little I know about automatic transmissions, it sounds like it's much easier to diagnose an internal engine problem than it is to diagnose an internal automatic transmission problem.
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Old 02-10-2009, 04:06 PM
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Thanks for the links. The rebuild kit looks like a good deal. How difficult would it be to do a home rebuild on one of these? I've rebuilt carbs, engines, and ancillaries, but have never rebuilt an auto trans before. I've always been told that they are best left to the "experts." I'd rather not have two projects going on at once (I'm in the middle of an engine rebuild), but if it's a relatively quick job (and as long trans overhauls don't require machining $$$), then it might be worth a try...
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Old 02-10-2009, 04:07 PM
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It shoulnd't be that much more labor,He has to change the lip seals anyway. With the new kit he can just stack the new clutch's and steels.
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Old 02-10-2009, 04:12 PM
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X2 on 302z28's comment. Do some more shopping.
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