Looking for advice: Noise in Park and Neutral

Hey all

I put this out to different F150 forums, but haven’t received much in response. I figured I’d post here too.


I have a 1995 F150 XLT with a 5.0 and 4R70W.

I rebuilt the 4R70W about 3 weeks ago (forward clutch pack was burnt out) and it has been driving perfectly fine. [Side note: flex plate was not removed during the rebuild.]

I noticed a few days ago that there was a noise whenever I revved the engine in park or in neutral. I recharged the AC last week and the noise wasn’t present when I was revving the engine in park.

Drive and Reverse are fine. It only happens when the transmission is not in gear. Transmission fluid level is good.

Here is a video of the sound: https://streamable.com/mho7p

Any ideas? As far as I can tell, it doesn’t affect driving performance, and doesn’t happen at idle.

—Day 2—

I used a mechanic stethoscope and seem to have isolated the issue to the bell housing where the flex plate sits. If it were something in that area, why would the noise go away in gear?

I also noticed that the transmission vibrates when the noise occurs, but I only hear it on the stethoscope around the bell housing.

Some theories were loose flex plate bolts or a cracked flex plate.

—Day 3—

I took the inspection plate off the bell housing and checked the flex plate to torque converter bolts. They’re nice and tight, and there isn’t any warping in the flex plate. I started the truck and noticed the noise wasn’t coming from the inspection hole.

I used my stethoscope again and seem to have isolated the issue to the starter. It seems to be coming from where the starter teeth contact the flex plate.

This is what the starter looks like: http://imgur.com/6OZvFju

I took the starter to the store and they bench tested it for me. It’s engaging and disengaging perfectly fine.

—Theory—

I wonder if there is a short somewhere in the system causing it to remain engaged or partially engaged. Is this possible? I thought the starter solenoid was simply an on/off operation?

Could the reason why the noise isn’t present in gear be because the neutral safety switch cuts power to the starter?

I’m going to run a multimeter to the starter solenoid and solenoid switch on the fender this afternoon.

What do you guys think?

Ford with a divorced start solenoid? Yeah that sounds like it could be a good place to start.

From the video it almost sounds like something rattling - have you checked that the trans dipstick tube and transmission hard lines are secured? Also, was the torque converter removed from the flexplate? I assume you checked that the torque converter bolts were tight when checking the flexplate bolts?

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Thanks for the input @hasbridge

Flexplate never came off, and torque converter bolts were the first thing I checked.

I didn’t specifically check the dipstick tube or fluid lines, but wouldn’t the noise occur in gear as well?

Theories:
longer-than-spec torque converter bolts: tight, but not actually clamping down on the flexplate
missing/incorrect ‘block plate’ /starter shim (should have come off, so should simply go back on, but sometimes folks misplace or lose them.

Thanks @jast

I don’t recall seeing a shim when I removed the starter to remove the transmission, but I’ve thought about getting a few washers to experiment with.

The torque converter bolts are the same ones I removed, but it’s entirely possible that they’re not tight enough. That’s also something I can experiment with.

When I checked the bolts, they were tight enough to spin the flexplate when I tried to tighten them further. Not sure how I could keep it from spinning. Leave it in gear and apply the handbrake?

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That will not be helpful for holding the torque convertor while tightening the bolts, just like sitting with the brake on with trans in gear normally. Instead a flexplate locker is usually used (or if you’re an acorn dodger like me, use a prybar to hold the flexplate from spinning, e.g. bracing against one of the ring gear teeth).
I would encourage looking up the proper torque spec and doing your best to employ that, which should remove any doubt about their tightness.

Rampant spitballing follows:
Is it the same torque convertor? It is conceivable, but doubtful, that a reman unit needs shorter bolts. If so, I would have expected it to ship with them.(I’ve never actually seen this, just speculating).
Try smearing the end of the starter gear with some ‘blue’ (e.g. prussian blue, chemdye, sharpie, etc.) so you can see the wear pattern. Ditto the ring gear. It might show whether it’s subjected to abnormal contact. Hard part is that those parts kind of “crash together” during normal operation, so it’s not always so easy to tell…

@jast

Same torque converter.

I looked up the torque values. Apparently they’re supposed to be around 30 foot lbs.

I’m pretty sure they’re nowhere near that. Lol

I’ll need to find a way to brace the flex plate. That was what kept me from tightening them in the first place.

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@jast

Actually I take it back. They are definitely 30 foot lbs. I was thinking 30 newton meters.

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Waiiitaminute…THAT’S from the general. not the same as this Ford in question. notatall…

:wink:

He makes it look so easy, but that’s pretty much how it went together. Lol

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Have you ran it without the bell housing guard on? Maybe a harmonic vibration.

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@TBJK

When I use my stethoscope, it’s not coming from the guard or bell housing. it seems loudest right up at the starter.

I’m still waiting for parts to come in (and for weather to get less wet/windy/cold), but I appreciate any and all suggestions and theories.

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I replaced the torque converter last night and it fixed the issue.

I should have replaced it when I rebuilt the transmission. One of those ‘while you’re there’ kind of things…

Anyway, that’s what the noise was! A bad torque converter.

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