trans squeal before upshift while towing?
 

I just bought a much larger box trailer to haul my music/band stuff, went from using a 6x12 6' box with 3000# axle, to a 8.5x20 7'6" box tandem 5200#. I still have the old trailer and I think I may have to keep using it for a while until I buy a larger truck. Here is why:

Towing the empty 20' trailer back about 150mi, it was fine even at highway speed keeping up with traffic, 70MP. It weighs about 4000# empty.

Now with cargo in it, trailer weighs around 7000#. When accelerating or climbing a hill at highway speed, the trans will go to 3rd or 2nd, and just before it up-shifts I will often hear a squealing sound for a couple of seconds. It remains in the lower gear but sooner or later it will shift, or if I get off the pedal some, it shifts immediately. This only happens when the engine is like 4000 - 5000 RPM producing max torque, and it has happened both with and without tow/haul mode.

I think the squealing sound is coming from the trans, which I guess is kinda obvious. Fluid is fine and I service it often -- every 15k miles I either flush it, or drop pan and change filter. So it gets new fluid often. The "dummy light" for trans temperature has never come on and I do have the auxiliary transmission cooler that comes with the factory towing option.

The only real history this truck has is the transfer case actuator or position sensor failed, and it would not engage. The dealership warrantied it and they said somehow the malfunction also damaged the transmission input shaft seal, so they replaced the seal and, at my request, changed the filter.

I am pretty sure the squealing sound is the truck crying for mercy and telling me I'm going to damage it if I keep towing this trailer with it. Just looking for another opinion. I can wait until buying a bigger truck to start using this trailer if I need to. It will make my life a little harder to keep working out of the small one this summer, but not as hard as having my truck in the shop for a transmission rebuild!

Here is a picture of the rig, you can see it is not a small trailer, there is a huge wind area in addition to the 7000# weight:
Attachment 4100

Welcome to the forum.

What's the tow rating for the truck?

Chevy says 8400#.

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The maximum trailer weight for a 2005 K-1500 Suburban is 7,500 lbs. (page 4-65 in manual, available at: http://www.extendedgmwarranty.com/ow...t-Suburban.pdf).

The transmission may be begging for mercy. Does the squealing noise happen every time? The wind resistance needs to be taken into consideration too.

Louis
GM Customer Service

It only happens sometimes. When it does, it is always in a high-torque circumstance going from 2 to 3, or 3 to 4. But even then it won't always happen.

I don't know how to deduct from GCWR for wind resistance; I'm sure that would be a bit complex. Is there a rough guideline of any kind? This trailer has more rotating mass, too, a fact I realized as soon as I pulled it out of the parking spot at the trailer factory.

I am still having a tough time deciding between the '07 3500 Classic and a new '12. I think if they give me a good enough price on the '07 I'll take it but otherwise, I'll just keep using the small trailer until later this year.

7000lbs on a 7500lb rated truck you should be fine. provided you keep in in tow/haul and don't push it too much. I'd be most concerned about brakes.

now I just have to ask, are you positive it's not coming from the belt? I say this because of when you seem to hear the sound, high rpm, and shifting gears, you might before you go dropping all kinds of money on a new truck or transmission, get some belt dressing and make sure the belt ain't making no noise at the higher rpms. Just a thought anyhow.

:chug:

The serpentine belt? I'm pretty sure it is coming from underneath, but I can't reproduce the sound except with the heavy trailer. I guess I could replace the belt and have the shop peek at the pulleys and stuff. I've been told not to oil the belt but now that you mention it, there is an occasional squeak at idle from something belt-driven, maybe it's trying to tell me something. :)

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]--> I'm sorry; I don't have a guideline for deducting wind resistance. There are too many varying factors (size of trailer, weight of trailer, speed of vehicle, etc.).

Hicksvilleshick offers another great suggestion you may want to consider.

Keep us posted.

Louis
GM Customer Service

I think its the pitched roof and chimney on the trailer that is causing all the wind drag....:eek:
gotta love perspective pictures:p

Definitely don't put any oil on the belt unless you just want to see if that makes the noise go away and then you replace the belt. Not a big proponent of belt dressing other than as a troubleshooting tool or short term fix.

Might try checking the belt for severe cracking on the ribbed side and for hardness.