GMC C2500 Transmission Problems & Cost | 4L60E | 4L80E | Allison 1000 | 6L90

The GMC C2500 HD was equipped with the 4L80E transmission in early models and the Allison 1000 (6.6L) and 6L90 in later models. But they aren’t without their problems though, so let’s look at some of the most common GMC C2500 HD transmission problems, look at cost estimates and figure out what you can do about them.

Need a replacement transmission? Get an estimate for replacement transmissions and local installation. Look up your transmission model by vehicle make and model.

What Transmission Do I Have?

GMC C2500 HD Transmission Models

GMC C2500 HD: 4L60E Transmission
GMC C2500 HD: 4L65E Transmission
GMC C2500 HD: 4L80E Transmission
GMC C2500 HD: 6L90 Transmission
GMC C2500 HD: Allison 1000 Transmission

GMC C2500 HD Transmission Replacement Cost Estimate

Pricing varies by model. To be 100% sure on pricing, have your VIN# handy and use our Get An Estimate feature to look up your transmission by VIN#.

Replacement GMC C2500 HD Transmission Prices:

What are the DTC codes related to GMC C2500 HD transmission problems?

GMC C2500 HD Transmission Recalls

None Found

GMC C2500 HD Technical Service Bulletins (TSB)

TSB 01-07-30-002C – Transmission stuck in third gear with inoperable instrument cluster and multiple DTC’s – 4L60E Transmission & 4L65 Transmission
1999 – 2003 Cadillac Escalade – 2002 – 2003 Cadillac Escalade EXT – 2003 Cadillac Escalade ESV – 1997 – 2003 Chevrolet Silverado – 1997 – 2003 Chevrolet Suburban – 1997 – 2003 Chevrolet Tahoe – 1997 – 2003 Chevrolet Blazer – 1997 – 2003 Chevrolet Express – 1997 – 2003 Chevrolet S10 – 2002 – 2003 Chevrolet Avalanche – 2002 – 2003 Chevrolet Trailblazer – 2002 – 2003 Chevrolet Trailblazer EXT – 1997 – 2003 GMC Sierra – 1997 – 1999 GMC Suburban – 1999 – 2003 GMC Yukon XL – 1997 – 2003 GMC Yukon – 1997 – 2001 GMC Jimmy – 1997 – 2003 GMC Savanna – 1997 – 2003 GMC Sonoma – 2002 – 2003 GMC Envoy – 2002 – 2003 GMC Envoy XL – 1997 – 2003 Oldsmobile Bravada
Problem – Vehicles equipped with the 4L60E and 4L65E transmission may become stuck in third gear, the instrument cluster may not function, and the following DTC’s may be set: P0740, P0753, P0758, P0785 and P1860.
Solution – The most likely cause of this transmission problem is a blown fuse or an open on circuit 1020 between the fuse panel and the transmission. If no battery voltage is found at the fuse, the ignition switch will need to be replaced

TSB 00-07-30-022D – No reverse, second or fourth gears – 4L60E Transmission & 4L65E Transmission
1993 – 2005 GM passenger cars and light duty trucks
Problem – Drivers may experience the loss of reverse, second and fourth gears. First and third gears will seem to function normally
Solution – The reaction sun gear may fail inside of the sun shell. It will need to be replaced with a stronger heat-treated 4L60E / 4L65 sun gear.

TSB 01-04-17-004B – Clunk, bump or squawk when vehicle comes to a stop, or when it is accelerating from a complete stop – 4WD/AWD vehicles with a one-piece propeller/drive shaft only
1999-2004 Cadillac Escalade, Escalade EXT, Escalade ESV – 1996-1999 Chevrolet 1500 Series Extended Cab Short Box Pickup (Old Style) – 1996-1999 Chevrolet 1500 Series Regular Cab Pickup and Utility Models (Old Style) – 1999-2002 Chevrolet Silverado Extended Cab Short Box (New Style) – 1999-2004 Chevrolet Silverado 1500 Series Regular Cab (New Style) – 2000-2004 Chevrolet 1500 Series Avalanche, Suburban and Tahoe – 2001-2004 Chevrolet Silverado 2500/3500 Series Regular Cab with Long Bed or Extended Cab (New Style) – 2001-2004 Chevrolet Silverado 2500 series crew cab, short box (New style) – 1996-1999 GMC 1500 series extended cab short box (Old style) – 1996-1999 GMC 1500 series regular cab pickup and utility models (Old Style) – 1999-2002 GMC Sierra extended cab short box (New style) – 1999-2004 GMC 1500 series Yukon, Yukon XL – 2000-2004 GMC Sierra 2500/3500 series regular cab with long bed or extended cab (New style) – 2001-2004 GMC Sierra 2500 Series Crew Cab, Short Box (New Style) – 2003-2005 HUMMER H2
Problem – In vehicles equipped with 4WD or AWD, drivers may experience a clunk, bump or squawk noise when they come to a stop, or when accelerating from a complete stop. This may occur during the 2-3 upshift or 3-2 downshift.
Solution – Replace the rear driveshaft slip yoke with a more robust nickel plated slip yoke.

TSB 05-07-30-017B – Water contamination – 2004-2006 GMC Sierra 2500 HD 4L60E
Problem – A common transmission problem occurs when the transmission shudders/shakes between 40 and 50 mph, as the torque convertor clutch engages. This is caused by rain water getting into the transmission through the dipstick.
Solution – The air inlet grille panel will have to be modified according to the procedure outlined in the TSB.

TSB PIP4051C – Harsh Shifting – GMC Sierra 2500 HD 4L60E
Problem – Unusually harsh gear changes, combined with a P0717 DTC for an input shaft speed sensor error, are often caused by damage to the ISS sensor wiring.
Solution – If wire damage is found (usually to the white wire), the wiring and sensor will have to be replaced. The pump cover should also be examined for sharp points/edges that could damage the wiring. If any are found, they should be smoothed with a file.

TSB 04-07-30-028A – Transmission fluid leak from reverse servo cover – 4L65E
Problem – An ATF leak can occur under the vehicle during cold weather (temperature below 20°F/6.7°C), due to a failed reverse servo cover seal.
Solution – To remedy the problem, an upgraded (see: better quality) reverse servo cover seal will have to be installed.

TSB 08-07-30-016 – Slipping, refusal to shift, overheating GMC Sierra 2500 HD 4L80E
Problem – Slipping between the gears, overheating, refusal to shift out of a gear, and/or DTC P0894 or P0218, may be because by friction material debonding from the torque convertor clutch (TCC).
Solution – If the friction material has circulated throughout the transmission, the entire transmission may need to be replaced. It is possible to remove the material from the internal components (like transmission cooler lines and the valve body), but it depends on the extent of the damage.

TSB 08-07-30-001 – 2001-2006 GMC Sierra 2500 HD 4L80E
Problem – Harsh or delayed shifts, slipping, no forward/reverse gears. Possible DTCs: P0741, P0742, P0751, P0752, P0756, P0757, P0894.
Solution – Rebuild or replace the valve body.

TSB 08-07-30-015 – 2002-2007 GMC Sierra 2500 HD 4L80E
Problem – Harsh shifts, delayed 2-3 shifts, 2-3 shift flare, no 3rd gear, slips in 3rd gear or reverse. Possible DTC 0757.
Solution – If none of the issues described in Bulletin 08-07-30-001 are present (debris in #11 checkball, leak in oil circuit, damage to the direct clutch), then replace the 2-3 shift solenoid due to a possible sticking pintle.

TSB PI488C – No forward or reverse and/or slipping – 6L80 Transmission | 6L90 Transmission
2010 – 2014 Cadillac CTS-V – 2010 – 2014 Cadillac Escalade (all models) – 2010 – 2013 Chevrolet Avalanche – 2010 – 2014 Chevrolet Camaro – 2010 – 2014 Chevrolet Corvette – 2010 – 2014 Chevrolet Express – 2010 – 2014 Chevrolet Silverado – 2010 – 2014 Chevrolet Suburban – 2010 – 2014 Chevrolet Tahoe – 2011 – 2014 Chevrolet Caprice PPV – 2014 Chevrolet SS – 2010 – 2014 GMC Savanna – 2010 – 2014 GMC Sierra – 2010 – 2014 GMC Yukon – 2010 – 2014 GMC Yukon XL – 2010 – 2014 GMC Yukon Denali
Problem – Trucks equipped with the 6-speed 6L80 or 6L90 transmission may experience no forward or reverse engagement, or slipping between the gears.
Solution – This problem could be caused by a cracked or split transmission filter. If this is the case, the transmission pump should be disassembled and inspected for possible damage. Inspect for any of the following conditions: – scored pump rotor or pump vanes – scored pump cover or pump rotor pocket – cracked pump slide.

The transmission should also be evaluated for any possible distress to the clutches. GM’s testing and analysis found that split or damaged filters may be caused by a damaged transmission pump. This can send a high pressure fluid spike down the filter neck on a cold start, resulting in the filter body cracking or the filter seam splitting. The filter is not defective and this is not a filter quality issue. Important: Do not replace the filter without inspecting the pump. Failure to inspect the pump and clutches could lead to a repeat of this condition.

TSB 09-07-30-004J – Slips in Reverse or Third, Delayed Reverse or Drive Engagement, DTC P0776, P2715, P2723, Harsh 2-3 Shifts – 6L80 Transmission | 6L90 Transmission
2006-2009 Cadillac STS-V – 2006-2009 Cadillac XLR – 2006-2009 Cadillac XLR-V – 2007-2008 Cadillac Escalade, Escalade ESV, Escalade EXT – 2006-2009 Chevrolet Corvette – 2007-2008 Chevrolet Silverado – 2008 Chevrolet Suburban – 2007-2008 GMC Sierra – 2007-2008 GMC Sierra Denali – 2007-2008 GMC Yukon Denali – 2007-2008 GMC Yukon XL Denali – 2008 GMC Yukon XL – 2008-2009 HUMMER H2 – 2008-2009 Pontiac G8
Problem – Vehicles equipped with the 6L80 or 6L90 transmission may slip when Reverse is selected or have no/delayed reverse engagement, harsh shifts from 2-3 / 4-5 or slips while in fifth, and slipping acceleration when passing. Possible DTCs include P0776, P2715 or P2723.
Solution – This transmission problem may be caused by a cracked 1-2-3-4 / 3-5-R clutch housing.

TSB 14043 – Thrust bearing failure – Allison 1000 Transmission
2012 Chevy Silverado HD – 2012 GMC Sierra HD
Problem:
Certain 2012 Chevrolet Silverado 2500HD / 2012 Chevrolet Silverado 3500HD and 2012 GMC Sierra 2500HD / 2012 GMC Sierra 3500HD trucks equipped with the Allison 1000 6-speed automatic transmission (MW7), may have been built with an incorrect transmission thrust bearing. Over time, this bearing could fail, resulting in noise and poor transmission operation.
Solution:
The bearing should be replaced with GM part # 29531106

TSB PIP3598C – Intermittent ratio codes or range inhibit – Allison 1000 Transmission
2007 – 2012 Chevrolet Silverado – 2001 – 2007 Chevrolet Silverado Classic – 2007 – 2012 GMC Sierra – 2001 – 2007 GMC Sierra Classic – 4WD Only
Problem – Drivers may experience intermittent no forward or reverse condition, the possibility of a flashing PRNDL display or a “range shift inhibited” message in the driver information center with no saved DTCs. Another possible symptom includes the following DTCs: P0729, P0731, P0732, P0733, P0734, P0735 & P0736
Solution – These Allison 1000 transmission problems may be caused by either an input speed sensor and or output speed sensor issue. The problem could also be caused by a mechanical issue inside of the four-wheel-drive transfer case like a worn bushing.

TSB 14308 – Leak at transmission cooler
2008 Chevy Silverado HD – 2008 GMC Sierra HD
Problem – Diesel powered 2008 Chevrolet Silverado 2500HD / 2008 Chevrolet Silverado 3500HD and 2008 GMC Sierra 2500HD / 2008 GMC Sierra 3500HD trucks equipped with the Allison 1000 6-speed automatic transmission (RPO MW7), may have a condition in which increased transmission oil cooling circuit pressure may cause transmission fluid to weep or leak. This loss of fluid occurs near the transmission cooler at the crimp joints on the metal ends of the cooler line where it joins the rubber hose. The increased oil cooling circuit pressure typically occurs while driving in extremely low temperatures.
Solution – Inspect and replace cooler lines if necessary.

TSB 04-07-30-018A – Ice buildup on shift cable – Allison 1000 Transmission
2001-2006 Chevrolet Silverado 2500HD – 2001-2006 GMC Sierra 2500HD
Problem – In cold climates, it may not be possible to shift the transmission after operating it in snow, slush, or icy conditions. This is likely due to ice buildup around the shift cable-to-manual shaft connection.
Solution – Install an aftermarket transmission shield.

TSB 06-07-30-013 – Shudder in 6th gear – Allison 1000 Transmission
2006 Chevrolet Silverado 2500HD – 2006 GMC Sierra 2500HD
Problem – Owners may experience a shudder occurs in 6th gear in 4Hi between 46 mph (74 km/h) and 49 mph (79 km/h).
Solution – Reprogram the TCM with TIS version 6.0 or higher.

TSB 08-07-30-049A – Transmission fluid leak from the ATF cooler – Allison 1000
2006-2007 Chevrolet Silverado Classic 2500 – 2007-2009 Chevrolet Silverado 2500HD – 2007-2009 GMC Sierra 2500HD
Problem – ATF leak coming from one of the transmission cooler lines.
Solution – Replace lines with updated design: GM Part #’s 20759971 (upper), 20759972 (lower), 20759971 (hose).

TSB 10-07-30-008A – Transmission won’t shift into overdrive – Allison 1000
2006-2010 Chevy Silverado HD – 2006-2010 GMC Sierra HD
Problem – Owners may experience a failure to shift into overdrive, or a 4-5 shift flare. Possible DTC P0777 or P0735.
Solution – Inspect and possibly replace the 3rd, 5th, and reverse clutch piston.

PIP4290A – Engine Stalling – Allison 1000
2007-2013 Chevrolet Silverado HD – 2007-2013 GMC Sierra HD
Problem – Owners may experience stalling or surging when stopped with the transmission in gear. Possible DTC P0742.
Solution – Inspect and replace the TCC solenoid and valve inside the valve body.

Common Problems with the GMC C2500 HD Transmission

Intermittent harsh shifting – GMC Sierra 2500 HD 4L60E
Problem – A common Chevy Silverado transmission problem is an intermittent hard 1-2 shift, often accompanied by engine bogging. This condition can be caused by the torque convertor clutch applying during the shift.
Solution – To remedy the problem, the wiring harness needs to be inspected from the transmission case connector to the rear of the engine on the driver side. It’s possible that the wires for the TCC solenoid and pressure control solenoid have become frayed on a body seam. If this is the case, the wiring will need to be repaired, and the harness repositioned.

Solenoid DTC’s – GMC Sierra 2500 HD 6L90E
Problem – A number of diagnostic trouble codes, including P0776, P0796, P2714 and P2723, can be caused by a pressure leak at the end of the clutch regulating valve.
Solution – The bore plug will have to be replaced with updated versions, or modified to accept an O-ring kit.

Lack of Response
Leaking Fluid
Low Fluid
Burning Smell
Grinding or Shaking
Whining, Clunking or Humming
Refuses to Go Into Gear
Torque Converter Issues
Valve Body Issues
Transmission Noisy in Neutral
Gears Slipping
No 3rd or 4th Gear
No 1st or 2nd Gear
No Reverse
Dragging Clutch
Trouble Codes / Check Engine Light

Can I drive with a transmission problem?

If your GMC C2500 HD can still make it up and down the road, you might say “It’s fine, I’ll just drive it until I can get it fixed”. But that is not always a good idea, depending on the symptoms. You see, there are a lot of (very expensive) moving parts inside of a transmission, and if something isn’t right, continuing to drive with a transmission problem could damage something else.

How often does a GMC C2500 HD transmission need to be replaced?

The overall lifespan of a GMC C2500 HD transmission largely depends on how well it was maintained. Factory design flaws also factor into this equation, along with how/how hard you drive. But on average, we’ve seen the GMC C2500 HD transmission last for between 130,000-180,000 miles. A high quality replacement transmission however, can last considerably longer if all of the factory design flaws have been addressed and the vehicle has been maintained.

How are GMC C2500 HD transmission issues diagnosed?

It is fairly easy to guesstimate what the root cause of your GMC C2500 HD transmission problems might be, but you won’t truly know unless you have the right tools and experience. A good mechanic or transmission repair center will be able to connect your truck to a computer and find out which diagnostic trouble codes (DTC’s) have been stored. Once they know what to look for, they can perform a visual inspection to verify the problem.

How is a GMC C2500 HD transmission replaced?

In order to replace your GMC C2500 HD transmission, the truck has to be lifted from the ground in order to gain access to all of the parts that will need to be unbolted. Then the transmission can be lowered to the ground (typically with a transmission jack), so the new transmission can be installed. Once it is in place, for the 6L80, the vehicle PCM will have to be reprogrammed / reflashed to accept the new transmission using the latest GM subscription.

Recommendations for GMC C2500 HD transmission issues?

To save time and get back on the road faster, have your 17-digit truck VIN# handy and you can get an online quote for a reman GMC C2500 HD transmission here, then find a local shop using our Find a Shop guide to install it for you.

How to Solve GMC C2500 HD Transmission Problems

Solution A: Buy a Used GMC C2500 HD Transmission

The quickest way to fix your transmission problems is to simply buy a used transmission or used transmission. These can be found at most junk yards, and they often come with a 30-90 day warranty. However, there’s no way to determine the actual condition of the internal components, so you could be spending a bunch of money to have the exact same problems. Plus, that warranty only covers the transmission if it’s defective, not the labor costs that you’ll have to pay.

Solution B: Buy a Rebuilt GMC C2500 HD Transmission

Another option would be a rebuilt transmission or rebuilt transmission. A local repair shop will remove your transmission, then install a bunch of new parts during the rebuild. The problem here is, the skills and experience of each transmission rebuilder will vary widely from shop to shop, so you could have problems from something that wasn’t adjusted properly. And the 1-2 year warranty might only cover you at certain transmission repair shops, in a specific geographical area.

Solution C: Buy a Remanufactured GMC C2500 HD Transmission

Many owners depend on their vehicle to commute and get things done. Their gasoline engines are designed to go 100’s of thousands of miles, so it makes sense to invest in a remanufactured transmission.

Need a replacement transmission? Get an estimate for replacement transmissions and local installation. Look up your transmission model by vehicle make and model.

What Transmission Do I Have?

What Problem Does Your GMC C2500 HD Have?

Let us know the year, mileage and problem you’re having as well as any trouble (OBD) codes you’ve found. If you’ve been given a quote or paid for a repair, we’d like to hear about that too!