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USD 205.95
Part #: XD309

XDP X-TRA Cool Direct-Fit Transmission Oil Cooler XD309

2001-2005 GM 6.6L Duramax
Part #: XD309
★★★★★ ★★★★★ 15 Reviews
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The XDP X-TRA Cool Direct-Fit Transmission Oil Cooler XD309 is a direct upgrade for the factory transmission oil cooler in your 2001-2005 GM 6.6L Duramax LB7/LLY.  XDP’s XTRA-Cool Transmission Oil Coolers are made using techniques borrowed from the HD and semi-truck industry to provide you with the ultimate in strength and durability. Built for more than just increased strength, the XD309 features a high-efficiency core that is specially designed to maximize transmission cooling potential over the factory unit. Each kit comes ready to install with the needed fittings, brackets, and hardware to make this a bolt-on installation for your GM Duramax/Allison powetrain. 

  • Direct-Fit 
  • Replaces Factory Cooler
  • Upgraded Design For Increased Durability
  • High-Efficiency Core To Maximize Cooling 
XD309 Specifications:
Core Width: 12-1/2" 
Core Height: 7-3/4" 
Core Thickness: 2" 
Overall Length: 16" 
Cooler Fittings: 7/8-14 UNF  

Application Notes:
XDP cannot guarantee fitment with all aftermarket transmission lines.
Please match aftermarket lines with the cooler fittings specified above.

Warranty Info:
Products manufactured by XDP carry a 1-Year warranty against defects in materials and craftsmanship. The Warranty is Limited to one (1) year from the date of sale and limited solely to the parts contained within the product's kit. Click Here for full warranty policy.

Vehicle Applications

2001 Chevy 6.6L LB7 Duramax
2002 Chevy 6.6L LB7 Duramax
2003 Chevy 6.6L LB7 Duramax
2004 Chevy 6.6L LB7 Duramax
2004.5 Chevy 6.6L LLY Duramax
2005 Chevy 6.6L LLY Duramax
2001 GMC 6.6L LB7 Duramax
2002 GMC 6.6L LB7 Duramax
2003 GMC 6.6L LB7 Duramax
2004 GMC 6.6L LB7 Duramax
2004.5 GMC 6.6L LLY Duramax
2005 GMC 6.6L LLY Duramax


  • MFG. Number XD309
  • Manufacturer Name XDP
  • Shipping Weight 5.00 lb.
  • Shipping Length 18 in.
  • Shipping Width 13 in.
  • Shipping Height 4 in.
  • Fuel Type Diesel
  • UPC 856217008489
  • Warranty Yes
  • Warranty Info 1 Year / Unlimited Mileage
  • Prop 65 WARNING: Cancer & Reproductive Harm -
  • Cross Reference # 89040217


★★★★★ ★★★★★
4.7/5 Stars out of 15 Reviews
Definitely recommend.....BUT....
(ABQ, NM) | July 16th, 2021
I do highly recommend this transmission cooler. I have a 2005 LLY and I Live in ABQ, NM and it gets hot here. My stock cooler was getting up to 210 sometimes before I got home from the 27 mile drive from work (in 100 degree temps).....even with a fan attached. I expected quite the temp drop after I read all the reviews. My temp still gets up to 200, however, I have noticed it does heat up slower and cools down faster. Haven't done and long distance or towing with it yet. It's a quick swap, a well built cooler (MUCH better than stock), comes well packaged and I think it will do much better when the temps settle back into the 80's. I will admit that my tune may have something to do with the trans temps. I will be testing that theory soon. Giving it the benefit of the doubt with 5 stars. Almost gave it 4 because I didn't experience what others did. Regardless of being disappointed, I still think it's worth the money and highly recommend this trans cooler. BTW- it's so well packaged, the other items I ordered were destroyed (crushed air filter and rad additive bottle busted open) along with the main shipping box, however, the cooler came through without a scratch. I called XDP and told them about the damaged items.....replaced without question. Great customer service!!!! Thanks XDP!!!!
01 Duramax
(Utah county) | July 11th, 2021
Was for sure bigger fit great hooked up easy, didn’t change my temps tho I’m running the same as before so that stinks. Wasn’t happy with that part. I don’t know what I’m doing differently then those others to not get good results but I’m not.
Transmission cooler
(18851 pa) | June 17th, 2021
Its cheeper then stock twice as big and lot more heavy duty would recommend it
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Questions and Answers

Will this fit a 02 Silverado 2500 hd with the 8.1 liter with the allison trans?
View Staff Answer 
We can only confirm fitment of the XDP X-TRA Cool Direct-Fit Transmission Oil Cooler XD309 on the 2001-2005 GM 6.6L Duramax trucks. Unfortunately, we don't have a direct-fit replacement that we can guarantee also fits gas models.

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