torque converter or flex plate question

[Darrell Goodwin]

I swapped the engine in my '82 C10, from a 305 to a 350. The 350 came out of a 4wd '91 suburban, but it wasn't the original engine. Anyway I bolted a new flex plate to the 350, then the '82 torque converter and tranny onto that then installed into the truck as a unit. It starts right up, but it began making a loud metallic noise. I pulled the transmission and realized the flex plate is warped. It was a new one, I torqued it to spec, everything seemed OK, but obviously something isn't right. What could I have done wrong? Can I press the flex plate back into flatness and re-use it? Since the torque converter slides into the transmission easily, what caused the warp? The older torque converter and the newer one look the same, and what I measured all matched. The new flex plate matched the bolt hole pattern of the one from the 350; the old one from the 305 had a smaller center hole. If I just get another new flex plate, what should I look for when installing the transmission to avoid warping or any other problems?

 

[bucket]

You might not have had the torque converter fully seated into the transmission. That will force the flex plate into the back of the engine.

Or, the pilot on the torque converter may not be sliding into the register on the crank flange. If so, that will bend the flex plate away from the engine.

 

[Darrell Goodwin]

Thank you, Bucket. It was bent away from the engine. I will re-install it with a new flex plate and make sure it slides into the register notches. It must have become misaligned as I lowered it into place. This time I will raise it into place on the jack, as the engine is already bolted in.

 

[bucket]

I've got a truck that for whatever reason, the torque converter would not mate up to the flex plate when I installed the engine. It just wouldn't slide close enough. I could feel the pilot bottoming out. All I did was install a couple washers on each bolt, as spacers. I intended to look into the cause after a few test drives... but I forgot about it until now actually and it's been a couple years and several thousand miles. Lol.

 

[Darrell Goodwin]

I'll keep that idea in mind. The new flex plate is only $ 39 + tax at autozone, but I heated the warped one (not red-hot, just too warm to touch) and stacked about 100# of weights on it. If the center is flat and parallel in the morning, I'll re-use it, but if there is any indication of a warp, I'll replace it.

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I think the torque converter will bolt on OK, inserting the transmission onto the shaft without binding will be the challenge. In my younger days, I'd roll it onto my chest and wiggle it as needed, but those were manual and this automatic is heavier. The transmission jack will support the weight, and I'll take the time to do it right. Maybe it would be better to put the torque converter into the tranny and then maneuver that to align with the flex plate? That way I can be sure that the notches are engaged. Any suggestions?

 

[bucket]

I'll keep that idea in mind. The new flex plate is only $ 39 + tax at autozone, but I heated the warped one (not red-hot, just too warm to touch) and stacked about 100# of weights on it. If the center is flat and parallel in the morning, I'll re-use it, but if there is any indication of a warp, I'll replace it.

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I think the torque converter will bolt on OK, inserting the transmission onto the shaft without binding will be the challenge. In my younger days, I'd roll it onto my chest and wiggle it as needed, but those were manual and this automatic is heavier. The transmission jack will support the weight, and I'll take the time to do it right. Maybe it would be better to put the torque converter into the tranny and then maneuver that to align with the flex plate? That way I can be sure that the notches are engaged. Any suggestions?

Definitely install the torque converter to the trans first. Besides being easier, there's no risk of damaging the input seal or the front pump.

 

[Darrell Goodwin]

OK, that's what I'll do. I put the new flex plate onto the crankshaft today, torgued to 65 ft-lbs, then helped somebody with a different project. I did start the engine with just the flex plate attached, the horrible noise is gone, although there is still some squeaking. The guy I helped today will help me locate the source of the squeak tomorrow. Then I'll do as you said, yes I can see why that's better. I thought this engine swap would take a few days; it's been over six months and I've run out of steam, so your advice means a lot to me and I appreciate it. I'm 71 and started working on cars when I was 15, when an 8-year-old '57 Chevy could be had for $75 or so. I'm glad for younger helpers, but sometimes they think they're done when there is still a lot left to do, and often need supervision. Apologies for going off-topic, I respect the experience of the members of this group, and I've learned a lot here. Thank you, Bucket, and all the other members who contribute their time and knowledge to keep these classic vehicles on the road.

Chevrolet - the Heartbeat of America.

 

[PrairieDrifter]

If it's bent away from the engine I would say the pilot of the torque converter was or is engaging the the flexplate too much. Then the bolts pulled the outside towards the converter. Did you have the flexplate oriented correctly, like front to back?

 

[Darrell Goodwin]

Thank you PrairieDrifter. It was bent away from the engine. I replaced it with a new one today. It bulges out in the middle about a 1/4" or so (after leaving weights on it overnight), but for $40 I felt more comfortable with a new one rather than re-using the slightly damaged one. Autozone might give me a warrantee refund, but clearly it was my error, not a defective product. I mounted it so that the side with the counterweight is toward the engine. That lets the "smooth" side face toward the torque converter. I didn't find a picture in the Haynes manual or in my PDF copy of the factory service manual, though I easily could have missed it if it's there. Let me know if I got it wrong, I'll probably help the other guy with the Pontiac first tomorrow, then he will help me with this after the day warms up (starting to get chilly nights in Colorado...) I'd rather get it right before going any further. The flex plates listed in the Autozone catalog for my '82 don't match the bolt pattern for the replacement engine, which I think is an '86, so of course I got one that fits. I'm keeping the '82 tranny because the donor vehicle is 4wd and mine is 2wd. The torque converters appear identicle, I measured the pilot shaft diameter, length from the central hub, the overall length front-to-back, and the overall diameter of both, and that all matches, so the difference in transmissions shouldn't be an issue, right?

 

[idahovette]

Maybe check the torque convertor snout into the end of the crank, make sure the convertor sets flush with the flex plate??

 

[Vbb199]

I just want to throw this out here...... after i built my TH400 for my 79', when i went to mate it to my bbc for the first time, the piloted 6 lug converter i installed wouldnt seat in the crank.... i ended up learning after pulling the trans there was a little metal cap in the back of the crank preventing it from seating ......

I kept that little cap for laughs

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This may not be your problem, as for whatever reason some converters dont quite interchange with all flex plates

 

[Darrell Goodwin]

That's quite a souvenir, Vbb199. It sure looks like a keeper. I will be sure to give a very careful inspection before proceeding. Kinda looks like the back side (actually forward-facing side) of the torque converters.

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I will definitely make sure there is proper clearance before using the wrench. Thanks for sharing. Good lookin' out.

 

[MikeB]

When installing the converter on the trans, be sure to keep turning and pushing until it fully engages the pump. And it should not protrude from the transmission.

Here's some text from an article I found:
The torque converter must be installed and fully seated in the transmission before it can be installed in the vehicle. This may take several minutes, because you need to align the input shaft, stator shaft, and oil pump drive. Turn the converter while pushing it rearward at the same time.

Here's the article:

GM Turbo 350 Transmission Installation Guide

As with most things associated with this hobby, installation takes much longer than removal. You’ll see the biggest benefits of using a lift and transmission jack for transmission installation. It can lift the unit slowly and then support the weight for hours while you get everything lined up...

www.chevydiy.com

 

[Darrell Goodwin]

Thank you MikeB. That is a very good article with a lot of detailed advice.