In my experience the tc will sit still while you idle the motor but it may chatter on the snout if you rev it up. I dont run em for long like that but it should be enough to tell you if the out of balance condition is coming from engine or converter
CK5
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New flexplate and tc wobble.
- Thread starter rhinoblzr
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The crankshaft should only be able to move front/back a few thousands of an inch, any more than that is very bad. If you can feel it by hand, that's usually a whole lot more than a couple thousandths.
If it moves that much, bearings are bad or worse.
If it moves that much, bearings are bad or worse.
Been there. Your thrust bearing (and probably the rest) are done for.
Does your new transmission run full line pressure all the time?
Does your new transmission run full line pressure all the time?
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Right on thanks. Been wrenching for months on this thing. Whats a couple more i guess. Time to learn engine building. Before i go crazy and spend a year of research and adding aluminum heads etc. How pints of blood is it to just add bearings? Machine shop work?
If the TH400 runs full line pressure and the converter feed isn't restricted a bunch, it will kill the thrust bearing in no time. The higher line pressure puts more pressure on the torque converter, which pushes on the flex plate which pushes on the crank.
The right way to do it is to put a pressure gauge on the cooling circuit (the cooling circuit goes through the torque converter and then out to the cooler), then compare your torque converter pressure to crank thrust (psi x in^2) and compare to what your engine is built for (different engines have different specs but a few hundred pounds is usually tops). Then drill/tap a piug into the converter feed with a much smaller hole. The details depend on restrictions in the cooler circuit and how strong the trans/pump are, unfortunately that part is pretty guess/check.
Full line pressure in TH400's is usually ~200 psi, you really want 50 psi or less in the converter/cooler circuit. TH400's are one of the few transmissions that don't limit converter feed pressure, if they're not built correctly they'll cook engine thrust bearings in short order.
The right way to do it is to put a pressure gauge on the cooling circuit (the cooling circuit goes through the torque converter and then out to the cooler), then compare your torque converter pressure to crank thrust (psi x in^2) and compare to what your engine is built for (different engines have different specs but a few hundred pounds is usually tops). Then drill/tap a piug into the converter feed with a much smaller hole. The details depend on restrictions in the cooler circuit and how strong the trans/pump are, unfortunately that part is pretty guess/check.
Full line pressure in TH400's is usually ~200 psi, you really want 50 psi or less in the converter/cooler circuit. TH400's are one of the few transmissions that don't limit converter feed pressure, if they're not built correctly they'll cook engine thrust bearings in short order.
When you drain the oil, you'll probably find a ton of brass looking metal. The thrust bearing is at the very rear on old school small blocks, you can drop the pan and confirm that one pretty quick/easy.
Thanks Chris, that's some good info on the th400. I was not aware of that. Looks like that crankshaft wants to jump outta there.
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Kinda sucks, all ive been dying to get to the fabricating part of this build. Bumpers, cage back half, sliders etc. Im a fabricator not a mechanic. You guys have any links to replacing the bearings. Im sure its not that bad, i've just havnt done bearings before.
Google and you tube will show you. A manual is your friend but you can also google all the torque specs. When you pull a cap and pop the bearing half out there should be a stamping on it. It'll say std. or .010 or .020 You'll want to make sure the new ones are the same. That goes for main and rod bearings.
You need to drop the pan and pull the bearing cap and see what you have.
If the crankshaft bearing surface looks perfect, you can put new bearings in it and change the oil often/soon. If there's any scarring on the crank, it's done (and won't last long if you put new bearings on a bad crank).
If the crankshaft bearing surface looks perfect, you can put new bearings in it and change the oil often/soon. If there's any scarring on the crank, it's done (and won't last long if you put new bearings on a bad crank).
If the TH400 is built wrong, it can kill the thrust bearing in 20 minutes.
It takes a lot of bearing damage to affect the reading on the gauge, once you notice it there things have been going south for a while.
