2 Hd Questions

[countryboy1365]

hey guys first off I want to say that I love the site, sounds verry informatave. Now for my 2 concirns. I have a 2007.5 all new 2500 hd and Ive got 2 problems. The first is a transmissoin noise that Ive had since day one. It sounds like an air-break releasing on a big rig when the trans downshifts when I go up hill, however it only does it when its cold. Ive had the truck to the dealer 2 times for this issue. The first time they reprogramed the trans controler per a tsb about a low temp trans noise and said they fixed it. The 2nd time they said it was a heat shield vibrating so they changed it. Now its about a month later and the noise is still present. My 2nd issue is that I have a vibration at highway speed say 60-75 this is a new development so the dealer hasent seen it yet. Does any of your trucks have either of these issues PLEASE HELP

 

Also how do I check if I have a limited slip I got the snow plow prep when I ordered the truck but it dosent seem like it catches. Is there a test that I can do? I know that on some trucks if you jack up the rear and spin the tires if they spin the same way theres a limited slip, is that the case whith the new trucks?

 

thanks guys in advance

[Shaners]

What tranny do you have? The Allison or the 4L80E?

 

If you have the RPO code G80 on the build sheet inside the glove box, then you ordered the "locking rear differential". It is a true locker and when it engages it usually locks with a pretty solid clunk and shudder.

 

You vibration could be a bad or out of balance tire/wheel. Or a possible out of balance driveshaft.

[ws6_guy]

pretty much what Shaners said everything I thought of he already posted.

[countryboy1365]

Thanks guys turns out I do have it weather its working properly or not I dont know Ii guess ill have them check it out when I take it in. Im assuming since I have the 6.0l and not the 6.6 d max that I have the 4l80E but my window sitcker says its the hydromatic 6 speed.

[s-ten]

You must have a 2007.5 in the new design. In that case it would be a 6L90E which is the same as the 6-speed hydromatic.

 

The G80 will lock only below 20-25 MPH and only when there is more then about a 250 RPM difference between the two wheels. The best way to tell if it is working is bring the truck somewhere that the tire are going to spin easily and then ease into the throttle until one wheel is spinning and the other is not. Eventually the tires will be spinning at different enough speeds where you will hear a clunk and you will feel the other wheel engage. Except in the weaker 1500 units they rarely have a problem with the G80, so I am sure it is working properly and you just have not noticed it yet.

 

As far as the vibration, I agree with everybody else on the tire probability.

[gman4dx266]

The G80 will lock only below 20-25 MPH and only when there is more then about a 250 RPM difference between the two wheels.

 

Is that new on the NBS trucks? If my 2002 HD gets loose on the interstate ill feel it lock, and then i can feather the gas and get it back in line.

 

Also, if you've ever did doughnuts in the grass, you'd find out the speed doesnt play a part in it either. :-)

 

...and no it's not the tcc locking.

[bad77]

The vibration could be an out of balance drivesaft. I have a 05 2500HD 4x4, Crew Cab 6.0l, 4l80e tranny, np261 transfer case.

 

I had a vibration that developed after about 15k miles at the same speed but was told the driveshaft looked to be fine. At 50k I had to have the rear transfer case seal replaced because of a leak then at 75k the tail housing bushing and seal. Each time I told the dealer that the truck had a vibration at about 60-75mph. It eventually got the point of resonating in the cab. Now at 86K the vibration had destroyed the transfer case and the slip yoke. The transfer case has now been rebuilt and new slip yoke and the driveshaft has been balanced, $1900 later. Don't let the dealer tell you it is nothing because that is what they told me.

 

Good luck

[djmercer1]

not to belittle your problem as it could be serious, but maybe you lost a wheel weight?

[Kodiak450]

All GM trucks and SUV's come with limited slip, unless is there different versions of limited slip that GM offers?

[Kodiak450]

Never mind I found out that GM uses two different versions of limited slip. The G80 which I gave uses a gear, vs the G86 uses clutches. Also read that people experience a noise similar to a .22 in the G80 when taking turns. I can't recall hearing any sounds, I'll drive around without the sound system on next time and see if I can hear anything. Also with the G80 some say the traction is very good, I guess that would explain why on occassions I am able to plow in 2wd as opposed to being in 4wd in my F250 all the time when plowing.

[wilkes65]

Here is a real good way to check if the locker is working, jack the rear end up on stands, put in gear and try to hold one of the tires still. I learned this on one of my older trucks when I was looking for brake noise. When you stop the one wheel you should hear a bang and the wheel should engage.

[Kodiak450]

Was curious of something. Whne it comes time to alternate, or change a tire I always find having a real hard time getting off the rear times sometimes. It takes alot of effort to bang the tire off. I wonder if this is caused my the G80?

[wellinghurst]

Was curious of something. Whne it comes time to alternate, or change a tire I always find having a real hard time getting off the rear times sometimes. It takes alot of effort to bang the tire off. I wonder if this is caused my the G80?

 

Mine stuck with my factory wheels a little, but never stick at all with my steel wheels. I don't have a G80.

[Kodiak450]

Perhaps aluminium sticks more.

[waltman]

The aluminum rims corrode next to the steel and sticks them together, a bit of grease or anti seize should do the trick.