Alarming rattle can noise from under truck

[Scott6]

Got some good work done today. Shafts off, Wire harness unhooked and pulled back, all the supports off, torque converter bolts removed. Tomorrow is drain fluid and drop her down. Still debating on removing the transfer case or not.

 

[Ozymandias]

I would, the Transfer is a heavy unit and has an odd angle on the transmission.

 

[Scott6]

Yea the case came off first. All in all this was really easy. I just took the transfer case off by hand, let it down on my chest and rolled it out. The trans just slid off super easy once I unbolted it.

The flex plate seems fine, no cracks, sounds good when you tap it with a mallet. So I guess converter? Kinda shooting in the dark here now.


Ohh the exhaust came off too, I could not get the bottom cooler line out without it. I bracket the 6.7 with jack stands, but it just sits there level on its cross member. Kinda rocks back and forth if I push it.

 

[Scott6]

Got the starter off for inspections also rear main time! Fun stuff.

anywho, this clicking in the starter kind resembles the noise but I highly doubt that’s the source, unless it’s rattling against the flex plate, but I highly doubt it.

Starter noise video

 

[Scott6]

Great news y’all! After cleaning it up I found cracks in the flex plate! $175 for a nice upgraded flex plate vs a new converter??? Yes please! (Although the billet BD plate amazon can get me in 2 days for $330 might be why I end up doing, I need this online this weekend if possible

explains why the truck was shifting just fine, it wasn’t the trans!

 

[petersonj]

Great find! Your perseverance paid off. Thanks for letting us know the results and for posting the pictures.

- John

 

[EDankievitch]

Everything you had said reminded me so much of how my 89 had failed. Cracked flexplate. I would do the converter also. You don’t know if the flexplate caused it to run off center. Cheap insurance being you’ve got it all apart.

 

[dieselshadow]

Nice!

 

[Scott6]

Everything you had said reminded me so much of how my 89 had failed. Cracked flexplate. I would do the converter also. You don’t know if the flexplate caused it to run off center. Cheap insurance being you’ve got it all apart.

I thought about it, but really It was barely cracked, the noise would go away fast (when it got heat). I’m betting the converter is fine.

also I’d like more miles out of my stock trans (95k) and I really didn’t want a no name rebuilt converter. When the times comes (hopefully not next week haha) I’ll pull it again and built it up right. Get a converter matched up with a valve body, pump, and new internals when she’s worn out. Especially now that I know how easy it is haha.

 

[GCroyle]

Scott6,

Nice pics of cracks. But why did it crack?

While trans is off, how about a good inspection of the engine to trans dowel sleeves and holes in trans for the dowels. Is the ring gear part of converter or flexplate? Look at tooth wear pattern all around. Just suggestions, it's in your hands.

On standby for final conclusion.

Gary

 

[Tuesdak]

Any witness marks on the starter from the flex plate being cracked and perhaps running out of true?

Do you have "snap test" emissions testing? The flex plates are known to fail on the IDI's I messed with during or shortly after the no load governor tests during emmisions.

You are absolutely correct to get the best aftermarket converter you can. Bluntly good converters cost money. They are real fun when set up correctly, but, a real PIA when they are out of balance or are heating the trans oil up like crazy due to a screw up in em. For example I sent in a video of the tach and all other gauges to YANK Converters when I was having trouble getting "out of the hole" due to a huge turbo. They sent me a high stall converter that was correct the first time for what I wanted. No additional coolers needed. Consider I owned one of the few not stock GM IDI 6.5TD that could do a burnout with a trailer on it. (Floor it, RPM comes up to turbo spool up RPM, wait a sec as turbo lights off, smoke clears from exhaust, and is replaced by tire smoke.) YANK Converters was the best $1200 I had spent on it. (and I already tried the BD Spool valve road). Don't know if they build anything for Cummins pickups, but, just helping you feel better about plunking your cold hard cash down for the highest quality converter you can get your hands on when the time comes.

 

[brucejohnson]

Scott6,

Nice pics of cracks. But why did it crack?

While trans is off, how about a good inspection of the engine to trans dowel sleeves and holes in trans for the dowels. Is the ring gear part of converter or flexplate? Look at tooth wear pattern all around. Just suggestions, it's in your hands.

On standby for final conclusion.

Gary

^^^^ What Gary mentions on the wear pattern of the gear teeth. If the flex plate was causing the noise by hitting on something like the sun/ring gear and starter gear there should be evidence of the contact and metal filings/dust with wear spots on the gears.

 

[Scott6]

No wear marks on the starter gear, the trans input shaft or the pump shaft. No metal shavings at all, the fluid was clean, pink and sweet-smelling, dowels look good to me (the look brand new actually) The trans has no temp problems (I run a gauge on the hotline out of the trans, old 47RE habit haha).

If I hold the flex plate firm to the ground tap the cracks, I get a bit of a popping squeaking sound. It is very obvious it's the same kinda noise, slower of course. I don't think it was hitting anything, or tweaking the converter. From the looks of it, I caught it early looking at pictures of other guys stock flexplates broken! I think it was the cracks themselves popping in and out of position until the metal expanded enough to silence them.

So, I ordered a BD Billet flex plate (Mainly because Amazon can get it to me Thursday). So that's one thing off the list for upgrades later. I'm going to put it in, put everything back together, new trans filters, new fluid and see how it does. I'm hoping its good and I get a lot more out of the trans. I'll start putting money into a new column for a proper trans down the road. Right now I would rather not spend $1200+ on a converter and I would really don't want to spend $550 on a "meh" converter. Especially if I don't have to.

If I'm wrong, well I'll take it all apart again, like I said before it was surprisingly easy. My main reason for getting it on the road is I need to take my 5th wheel in to get it weighted so we can register it here in TX just so I can sell it haha. Once I do that I won't be towing anything bigger than a ski boat for a while.

 

[petersonj]

I caught it early looking at pictures of other guys stock flexplates broken! I think it was the cracks themselves popping in and out of position until the metal expanded enough to silence them.

For what it's worth, I think you are right on here. After all it is a flex plate, so as those cracks grew, the flexing within the cracks themselves would definitely make noises (like your symptoms) under certain conditions.

- John

 

[Scott6]

What kind of Loctite should I use on the Flex plate bolts? It doesn’t look like there was any on there from the factory

 

[DavidC]

I would think blue.

 

[Ozymandias]

68 is a fine transmission and the converter by far not as horrible as the one in the 48RE.
Also Lockup is way more aggressive used on it, so it isn't a point to just change the Converter while one is in there.

 

[Scott6]

68 is a fine transmission and the converter by far not as horrible as the one in the 48RE.
Also Lockup is way more aggressive used on it, so it isn't a point to just change the Converter while one is in there.

I agree, I have been plenty happy with my stock 68rfe this far. Smooth, 6 speeds, tows like a boss compared my 2000/47re, also I’m not going to be towing for a while after this so even if it’s getting worn out, it’s got plenty for life left for the easy time it’s about to get for the next year or two.

 

[Scott6]

So if y’all don’t mind helping me some more. When it comes time to fill the trans, what’s a good process? I’m assuming it’s damn near empty, just wanna make sure I do this right. My new pan does have a drain plug if I overfill.

This is what I gather from reading:
1. Fill the converter with 1-2 quarts
2. Put the trans back on (lots of steps here)
3. Pick rest of truck together
4. Put 12 quarts down the fill tube
5. Start truck in neutral (parking break on)
6. Idle for a min or so
7. Check fluid and top off
8. Drive

it calls for 17.5 quarts so it should be ~5-6 quarts low

 

[Ozymandias]

68 is checked in Park - not N as the old stuff.
Set it on level ground and after first fill just let it idle for as long as you want and top off to the desired fluid level.
Doesnt matter for the last couple ounces. Within the min-max range is fine.