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Old 02-21-2013, 11:11 AM
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T-400 bushing question

I am in the process of doing a stock rebuild on a TH400, this is my first a/t rebuild. My concern is that after installing the center bushing (long tubular one) I went to install the shaft through the bushing and realize the fit was too tight for the splines to easily slide through. There was also a very slightly raised edge at one end which I was completely puzzled about. Anyway, I managed to “coax” the shaft through the bushing and passed the raised edge. The shaft did not spin freely at first. I applied oil, spun the shaft and moved it in and out of the bushing. I then completely removed the shaft and inspected the bushing, there were very light bushing shavings that I removed and the raised edges from the spline “damage” were gone but you could see where they were smoothed over by working it. At this point the shaft freely moves in an out of the bushing and also there is no resistance while spinning it. No damage to the shaft.

Is there reason to be concerned with continuing my build? Obviously I must have done something incorrectly when installing the bushing but after working the shaft in/out and spinning it, it seems that everything is fine. Just looking for opinions for those of you more experienced.

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Old 02-21-2013, 11:30 AM
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It'll be allright. Just be sure the bushing was installed in the right position whereas the slot in the bushing is in the same place that the center support feed hole is,and that the feed hole is not partially /fully blocked.
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Old 02-26-2013, 10:42 AM
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Thanks Rick. I think I was so concerned with that hole being lined up that I didn't see what caused that slightly raised edge!

Does anyone have a good reference for clutch pack clearances? I did not find much using the search function. My direct drum had 6 friction disks but my rebuild kit only had 5 for it. I was able to shim the pack and it looks like my clearance is about 0.075" according to the feelers. I am finding all sorts of mixed answers for what clearances should be but too tight is seems to be the bigger problem.

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Old 02-26-2013, 12:19 PM
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0.075" is just within tolerance for the forward/direct, according to the page below. IMHO you'd be better off buying an extra friction if yours will hold 6. I've reused a friction to fit, but that's me.

http://www.crankshaftcoalition.com/w...ack_clearances

Last edited by cobalt327; 02-26-2013 at 12:27 PM.
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Old 02-27-2013, 10:51 AM
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Yeah I think I will put the 6th friction disk in. However in order to use get the right tolerance I might need to use the thinner 0.078" plates. Are the thinner plates acceptable for the direct drum?
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Old 02-27-2013, 11:57 AM
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Yes,the thin plates will be fine....and be sure to put the new clutches in a pan of ATF for about 15 minutes before you put them in the trans.Ya don't want to install them dry.
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Old 03-09-2013, 04:26 PM
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A good rule of thumb on clutch clearance is to have .010 per friction on your clutch stack. So, if you have a 6 friction stack, you want a total clearance of .060 for that drum, 5 frictions .050, etc. It's better to have a bit extra clearance than not enough. Too tight creates heat buildup, your AT's worst enemy when it comes to longevity. As long as the shaft turns freely now, and the lube hole lined up with window in your bushing you should be fine. Sometimes bushings from different mfg's are loose on the tolerances (3 separate same bushings, all different tolerances) no sweat. Definitely take advantage of adding the additional friction to your drum if it allows rather than adding additional steel to get clearances correct...The additional holding force will greatly add to your tranny's durability.
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