I'm assuming if the flexplate fails, it happens for a reason.
-Are there ways to verify that the transmission wasn't compromised?
-Are there other parts to inspect that may have contributed to the flexplate breaking?

If my flexplate is cracked, would suck to replace it then find out my transmission is on its way out since replacing either seems to be about the same amount of work. Removing the inspection plate & dropping the pan seems like a logical starting point.

Symptoms:
-Slight slipping feeling when I was accelerating 65+mph on the interstate last night (only noticed it a couple times)
Edit: Could have been poor acceleration & not slipping.
-While in stop/go traffic I would occasionally feel a mild rumbling through the floor board with acceleration at slow speeds.
-Eventually started to hear rattling idling at stop lights. Rattling was more noticeable when I pulled into my garage. Rattling is present in D & R. In P or N the rattling is either really faint or gone completely
-No Cel or pending codes.

Possible causes of above symptoms:
1. Cracked flexplate & torque converter going bad?
2. Exhaust leak?

Last night was the first time experiencing those symptoms. I drove my wife's car into work this morning because I didn't want to create more damage or get stranded. Should have time this Friday to remove the inspection plate. @mtbtim & @infamousRNR have any input from your previous experience?


Update:
The rattling noise was coming from the bell housing area confirmed using a mechanic stethoscope but wasn't from a cracked flexplate. It was most likely from a bad torque converter. I say most likely because I tried testing it using the FSM instructions but wasn't able to reproduce the FSM results so I don't have an objective confirmation. I replaced my transmission with a new reman toyota trans which came with a new torque converter and symptoms have resolved. Confirmed that the flexplate was intact when I pulled my transmission.
P0770: Deciding on repair options

The flex plate can just fail over time. My buddies 1gen Taco had the flex plate fail after about 160k miles. He used an aftermarket flex plate that only lasted maybe 10k miles before failing again. Eventually he put a new OEM one back on and never had any issues with it until he sold the truck.

If the flex plate just cracked, I highly doubt it did any damage to the tranny. If it totally grenaded, I guess it could mess something up, possible the front pump?

Plenty of people have had flex plates go bad over time without any tranny damage.

Excessive run out on the crank shaft can also cause the plate to crack but that is super rare.

If your flexplate is just cracked then there was no damage to the transmission. Flexplates can crack for any number of reasons that aren't due to transmission problems. If you decide to replace the flexplate it would be an ideal time to look at your rear main seal and consider replacing that as well.

I agree with what others have said already. Even if the flex plate completely cracks, I doubt any damage would occur to anything other than maybe some scratches on the bell housing and torque converter.

@thegipper statement about the crankshaft bearing play is the only thing I think could contribute to causing a flex plate to crack. If you replaced a cracked flex plate and the new OEM one you installed also cracks somewhere soon down the road, that's what I would suspect is the culprit.

I would simply remove the inspection plate off the bottom of the bell housing and see what you can see. You can get onto the crankshaft bolt with a 19mm socket and 1/2" ratchet and turn the motor clockwise into different positions so you can see other parts of the flex plate. You'd want the trans in neutral for this. When @infamousRNR transmission imploded, I took the inspection plate off and tried using a borescope camera to be able to see more of the flex plate. I don't know if it was the cheap camera I had bought or the fact there's just very little room to get in there with the camera and get sufficient lighting to see good enough detail.

Let us know what you find out. We have that 3 Part Trans Replacement series you could use to get the trans out of your way to get access to the flex plate. We also have a recent clutch video (Part 2) you can use for information on how to replace the rear main seal.

Here's Part 1 of the Trans Replacement Series




Here's Part 2 of the Clutch Replacement Series

Good to know that the transmission should be ok assuming it is a cracked flex plate & that it can happen with age. Good tip on the rear main seal. Actually reading through other threads & making a list of other associated maintenance when removing the transmission.

If the flexplate and transmission pan seem to be normal, any suggestions on where to look next?

Appreciate the troubleshooting tip.

Trans in neutral, check.

Thanks for the video links & letting me know which vid showed how to replace the rear main seal. Seriously, was a huge help.

In your part 1 vid you mentioned that you didn't see any cracks in the flex plate, were you guys able to find out what caused the transmission failure?
Do you happen to know if his made a rattling noise at idle or with slow acceleration?

I'll probably end up getting a borescope too. Will let you know what I find.

A cracked flexplate will not cause any slipping feeling. The slipping feeling would likely be torque converter. A cracked flexplate (not a flexplate that is missing pieces etc) will cause a metallic rattling noise that can be a lot worse in certain rpm ranges. You would likely only be able to see the cracks with the transmission removed even if you had a good boroscope there are still a lot of blind spots without separating the torque converter from the flywheel If I were you I would replace the torque converter and rear main seal while I was in there. Since you have to separate the starter from the transmission it would be a good time to rebuild your starter as well.

Good point about the slipping. Is there a way to determine if the slipping is coming from the torque converter vs worn gears or other parts within the transmission? Trying to figure out if the symptoms I was experiencing was the start of my transmission going bad or if it could be resolved with replacing the flexplate & torque converter. Want to do my best to fix it right the first time. For the occasional shuddering on acceleration, would a broken flexplate or torque converter more likely be the cause of that?


This probably explains why on some of the threads I've read, people that thought they had a cracked flexplate weren't able to see evidence of it looking through the inspection plate. Can a bad torque converter make a metallic rattling noise?


Will add starter rebuild to the list. Thanks for that especially since I already have the parts for it.

Answers in bold. Always happy to help

What you described about a symptomatic torque converter seems consistent with what I was experiencing. The only thing you mentioned that I didn't experience was increasing RMPs. My RPMs seemed to behave normally from what I remember. Would the lack of surging RPMs further rule in or out the torque converter?

The stuff you mentioned about losing a gear or burnt fluid would be more indicative of an issue within the transmission instead of the torque converter or flexplate correct?

Also should mention no CEL or pending codes.

Answers in bold

I replaced mine as PM along with the rear main seal as PM while doing the front pump seal. So I'd do those at the same time if your flex plate is bad. I'd also do the transfer case shifter seat thingy at the same time. Tim has a video on the shifter seat he used a Marlin Crawler one which is way cheaper. The Toyota one you have to replace the whole metal thing.

A note on the inspection plate, one of the 4 bolts on the plate is extremely hard to get to. I put the plate back on with only 3 bolts (secure) since I never wanted to mess with that 4th bolt again.

When I had my torque converter on its last leg , the most apparent problem for me was the shudder around 35mph to 40 but devoid of any surging RPMs. It would feel like I was driving on a grated drawbridge. No noise. Trannny shifted well until I used Maxlife ATF in the tranny (gallon) one day and it began slipping. Switched to Castrol Import ATF, which is thicker. No problems for another three years.

If you can drain and fill the fluid through the tranny cooler, I would start with a drain and fill of ATF, using a gallon of new fluid, such as the aforementioned Castrol. Then go from there. When the eventual replacement came, a new tc plus rear main.

Still enjoying the Metabo?

No way, the info you provided has been very helpful & helping to make sense of the symptoms I was experiencing. Thanks for clarifying the RPM abnormalities in relation to a torque converter on its way out.


Thanks for the shifter seat mention. I wasn't aware of that one but will put it on my list.


Hilarious. I've never removed the inspection plate so appreciate the tip.


Have any opinions on Castrol import atf compared to mobil 1? I've been using mobil 1 for no specific reason but also not loyal to any brand so I have no problem switching to something better. And straight up, the metabo impact is the shit. Since then I've bought a metabo corded angle grinder that has a brake on it which stops the wheel pretty fast & extremely smooth to use, metabo corded die grinder which came in really handy when I was having my sliders built & a metabo drill. They make some pretty impressive power tools. Their impact is still my favorite & most used.