Disturbing noise when pulling uphill
09-11-2017, 11:20 AM
#11
Senior Member
220f is right in the normal temperature for the 6R80 transmission. Anything under 250f won't cause any indicated issue from normal operation. I hit 235f on both coolant and transmission temperatures during a long steep low speed climb over the summer.
As to the noise, I would definitely get the IWE system checked. Putting your foot to the floor causes the throttle butterfly to open wide and reduce vacuum in the intake manifold, which is exactly where the IWE system gets its vacuum for operation. your IWEs were trying to engage and due to lack of vacuum. The wheels were spinning while the shafts were not as they weren't engaged at the transfer case. I would suspect a bad check valve that is supposed to maintain vacuum during WOT moments. There are many splines that engage in the IWE so them bouncing over each other sounds like a higher pitched grinding noise.
As to the noise, I would definitely get the IWE system checked. Putting your foot to the floor causes the throttle butterfly to open wide and reduce vacuum in the intake manifold, which is exactly where the IWE system gets its vacuum for operation. your IWEs were trying to engage and due to lack of vacuum. The wheels were spinning while the shafts were not as they weren't engaged at the transfer case. I would suspect a bad check valve that is supposed to maintain vacuum during WOT moments. There are many splines that engage in the IWE so them bouncing over each other sounds like a higher pitched grinding noise.
Last edited by tcp2; 09-11-2017 at 11:51 AM.
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pdxF150 (09-11-2017)
09-11-2017, 12:32 PM
#13
220f is right in the normal temperature for the 6R80 transmission. Anything under 250f won't cause any indicated issue from normal operation. I hit 235f on both coolant and transmission temperatures during a long steep low speed climb over the summer.
As to the noise, I would definitely get the IWE system checked. Putting your foot to the floor causes the throttle butterfly to open wide and reduce vacuum in the intake manifold, which is exactly where the IWE system gets its vacuum for operation. your IWEs were trying to engage and due to lack of vacuum. The wheels were spinning while the shafts were not as they weren't engaged at the transfer case. I would suspect a bad check valve that is supposed to maintain vacuum during WOT moments. There are many splines that engage in the IWE so them bouncing over each other sounds like a higher pitched grinding noise.
As to the noise, I would definitely get the IWE system checked. Putting your foot to the floor causes the throttle butterfly to open wide and reduce vacuum in the intake manifold, which is exactly where the IWE system gets its vacuum for operation. your IWEs were trying to engage and due to lack of vacuum. The wheels were spinning while the shafts were not as they weren't engaged at the transfer case. I would suspect a bad check valve that is supposed to maintain vacuum during WOT moments. There are many splines that engage in the IWE so them bouncing over each other sounds like a higher pitched grinding noise.
Explained this way does make it sound feasible.
09-11-2017, 07:00 PM
#14
Senior Member
Imagine that.
At highway speeds the wheels are turning 600-ish rpm and the axle shafts/differential/driveshaft are turning zero rpm. A loss of vacuum (for whatever reason) will cause the IWEs to attempt to engage and a considerable grinding sound will result. This occurs specifically BECAUSE the front drive is disengaged at the T-case. If everything were spinning it would be a non-event. I didn't bother with a step by step walk through because I assumed (my bad) that those providing technical responses knew roughly how the system worked.
P.S. At no point did the OP say the noise was suspected as coming from the transmission. That ball was picked up and run with by others.
At highway speeds the wheels are turning 600-ish rpm and the axle shafts/differential/driveshaft are turning zero rpm. A loss of vacuum (for whatever reason) will cause the IWEs to attempt to engage and a considerable grinding sound will result. This occurs specifically BECAUSE the front drive is disengaged at the T-case. If everything were spinning it would be a non-event. I didn't bother with a step by step walk through because I assumed (my bad) that those providing technical responses knew roughly how the system worked.
P.S. At no point did the OP say the noise was suspected as coming from the transmission. That ball was picked up and run with by others.
Last edited by PerryB; 09-11-2017 at 07:24 PM.
09-11-2017, 08:37 PM
#15
He did say it came from under the cab.
The 99 F350 I had did have vacuum hubs, and they had a habit of engaging at times with no input, but they just clunked. I've never worked on the F150 hubs, so not familiar with their operation.
The sound appeared to be coming from directly below us in the cab.
09-15-2017, 09:48 AM
#17
Senior Member
Also happened to mine, steap climb, hit 6000+ rpm, second gear at 60 mph, feathered gas pedle and stopped instantly.
Bothered me when happened, pulled over to cool tranny right after the climb, never another indicatin on the trip of anything, So no worries.
Bothered me when happened, pulled over to cool tranny right after the climb, never another indicatin on the trip of anything, So no worries.
09-15-2017, 10:49 AM
#18
@martiangod yeah that's pretty much what my experience was. I'm camping again this weekend and will cross the coastal range again this afternoon.
If it happens again I'll take it in to the dealership to have them look over the vacuum check valves. Not something I want to do unless 100% necessary.
If it happens again I'll take it in to the dealership to have them look over the vacuum check valves. Not something I want to do unless 100% necessary.
09-15-2017, 03:03 PM
#19
$5 and no tools.
If you pull it off of the hoses, try to apply vacuum from the bottom.
I knew mine failed because when I did pull it off and sucked from the bottom I got air. It's supposed to flow from the bottom up hence pulling vacuum. The reason it grinder on you is because the vacuum reservoir had no vacuum to hold the system until the engine no longer required the power that you requested via the accelerator. There is a write up on here about this. Hence the reason I jumped from one site to this one.
Hope this helps...
Edit....it's the piece with the blue in it.
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pdxF150 (09-17-2017)