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Hello new to this forum from Windsor/Detroit area
:help
Have a 2007 GMC Classic 2500 HD 4wd crew cab long box with 6.6L diesel and Allison transmission

Not sure the best place to post in the forums, but started here first.
Have had a number of issues, but the three main ones are listed below.

1)Driveshaft replacement: The carrier bearing went and replaced it (dealer only part $250) and the u-joints, but the drive shaft is out of balance and they say is bent. Before straightening it or replacing it with a standard driveshaft, I was hoping to investigate and find opinions into options for other more heavy duty and/or carbon fibre shafts. Are there suggestions or experience with other driveshafts?

2)Calibration for Larger Replaced Tires: Another issue I have had was modifying the original tires (16.5”) with 18” rims and GY Wrangler LT275/70R18, E load rated tires. The oversized tires would change the stress on the components as well as the speedometer but more importantly the shifting of the transmission. I have gone several times over the past few years to GM truck dealership (even one of the mechanics which owns the same model could not get it re-calibrated) in an attempt to get the truck re-calibrated, but they say that the particular 2007 model Classic with the 6.6L/Allison can not be re-calibrated or adjusted. The speed has a differential of about 10% which the GPS identifies. Has anyone been successful in getting this model re-calibrated and by whom? Any information or contacts would be appreciated.

3)Fuel Gauge: For the past year and half, the fuel gauge does not work properly. Took it to the dealership and they say not covered under warranty but they know of the problem in many vehicles and can fix it but will not guarrantee it won't happen again. The gauge will show ¼ to 3/8ths of a tank but be out of fuel. Frustrating at times. Lately I have also found that even at half a tank and a few days go by without use, the fuel system seems to get air into it and dies out. By adding a gallon of fuel and fiddling with the primer for 10 minutes, it starts and runs fine again. Yes have changed the fuel filter. What has been others experience with? How much trouble is it (and what parts) should be changed to likely fix the problem?

Appreciate any leads or direction you can give me. Maybe there are other forum posts already on these subject matters but I did not find they yet.
 

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Hey CG, on nos2 , that size tire shouldn't bother anything in driveline. Look at what Hummer uses, 315/17, stock. Same driveline. Driveshaft, find a shop that custom builds drivelines. They will diagnois your drive-shaft better than stealership. 3) Sounds like a problem with your fuel pick-up in tank. May be time for a PPE custom pick-up. Good Luck.
 

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1)Driveshaft replacement: The carrier bearing went and replaced it (dealer only part $250) and the u-joints, but the drive shaft is out of balance and they say is bent. Before straightening it or replacing it with a standard driveshaft, I was hoping to investigate and find opinions into options for other more heavy duty and/or carbon fibre shafts. Are there suggestions or experience with other driveshafts?

Just get stock. They hold up very well

2)Calibration for Larger Replaced Tires: Another issue I have had was modifying the original tires (16.5”) with 18” rims and GY Wrangler LT275/70R18, E load rated tires. The oversized tires would change the stress on the components as well as the speedometer but more importantly the shifting of the transmission. I have gone several times over the past few years to GM truck dealership (even one of the mechanics which owns the same model could not get it re-calibrated) in an attempt to get the truck re-calibrated, but they say that the particular 2007 model Classic with the 6.6L/Allison can not be re-calibrated or adjusted. The speed has a differential of about 10% which the GPS identifies. Has anyone been successful in getting this model re-calibrated and by whom? Any information or contacts would be appreciated.

275's wont hurt the tranny. You may have to crank the torsion bars a few turns to clear the wheel. You can change the speedo with select programmers, while you can change shift points with EFI Live

3)Fuel Gauge: For the past year and half, the fuel gauge does not work properly. Took it to the dealership and they say not covered under warranty but they know of the problem in many vehicles and can fix it but will not guarrantee it won't happen again. The gauge will show ¼ to 3/8ths of a tank but be out of fuel. Frustrating at times. Lately I have also found that even at half a tank and a few days go by without use, the fuel system seems to get air into it and dies out. By adding a gallon of fuel and fiddling with the primer for 10 minutes, it starts and runs fine again. Yes have changed the fuel filter. What has been others experience with? How much trouble is it (and what parts) should be changed to likely fix the problem?

Kinda sounds like a sending unit
Hope this helps
 
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