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oldhickory 10-14-2012 12:42 PM

T-400 intermittent squeak rattle in park and drive
hello everybody. i posted a question before on hotrodders, and got some awesome help. so thankful for this site.

i've got a new problem, this time with my transmission. (i think)

I have an '85 chevy 3/4 ton 4x4. engine is a 402. tranny is a th400 that works great aside from being a little slow to go into reverse, and a slight leak from the the pump o-ring. (i think)

Here's the problem: When i start my truck, after the temp sensor on the block hits 150 +-, i hear what can only be described as a squeak/rattle. (sounds like a spun bearing almost, but it is very 'chirpy'.) It is intermittent, and usually goes away a couple of minutes after the thermostat opens up. the sound occurs in park, while the engine is at a fast idle, and also occurs in drive while at any speed, but goes away when i increase rpm's. The sound is definitely coming from the front of the transmission as determined by the screwdriver to ear test.

i call it a squeak/rattle, because it seems squeak more when going over rough patches in the road. again, the transmission seems to work fine, but the sound is getting louder, and i am beginning to notice a vibration while accelerating uphill. (no vibration apparent upon release of gas pedal.)

also, the torque converter has a bit of a wobble to it, which it has had ever since i bought the truck two and a half years ago.

One more thing to add: the other day it rained, and i drove in the rain, thoroughly wetting my undercarriage. The sound went away, and did not occur again for a couple of days. This caused me to think it is something external, but perhaps the humidity did something? I live in the dry desert of southern new mexico.

Sorry for all the words, but i have been searching hi and lo on many forums, and am about to pull the tranny, but just thought i'd put my problem out there.

I have tightened the flexplate to converter bolts, which were a little loose. i did not see any cracks. i have a suspicion that my TC bolts may be loose, thus causing the wobble?
Any suggestions would be greatly appreciated.:)

SSedan64 10-16-2012 06:47 AM

Flexplate to Converter bolts are the same as TC bolts. Did you intend to say Flexplate to Crank bolts?
If the TC was wobbling the TC nose may have been rubbing the rear of the Crank. Could also cause Trans Pump, Seal & Bushing damage.

oldhickory 10-16-2012 04:30 PM

Yes, i meant flexplate to crank bolts. I decided not to pull the tranny yet, but instead replaced the filter and so far (day two) the sound has not come back. But i did find 3 or 4 very thin aluminum shavings, as well as a gray film in the bottom of the pan mixed with lots of gold colored 'dust'.

I noticed yesterday that i am missing one bolt to the bellhousing, and there is a small gap between the bellhousing and block on the passenger side (1/8"). Can this be the cause of the issues i am experiencing?

SSedan64 10-17-2012 04:38 AM

It could be causing alignment issues. Also make sure the alignment Dowel Pins in the Block are there. 1 on each side.

oldhickory 10-24-2012 08:28 PM

All of the bellhousing bolts were quite loose, so i pulled them and replaced them with new grade 8 bolts and lock washers. It has been almost two weeks since changing the filter, and the sound has not come back. Thanks for the help guys.:thumbup:

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