THE MERCHANT AUTOMOTIVE ALLISON SOLUTIONRather than throwing out the baby with the bathwater the team at Merchant Automotive worked on eliminating the weak points in the Allison trans and building on the strong suits when developing the MAximum Transmission series of rebuilt Allison transmissions. Additionally, with any of these burnt clutches or overheating transmission scenarios there will be a lot of associated debris in the form of both metal and clutch material that will make matters even worse leading to a total failure. The internal clutch packs suffer a similar fate with slippage induced overheating and eventually burning the clutches to the point where they will not hold well enough to drive the truck. This can have a cascading effect that will eventually cause the torque converter lock-up to fail entirely. When the front cover distorts it reduces the contact area for the internal lock-up clutch disk which then slips, causing increased heat and debris to be sent through the transmission fluid into the rest of the transmission. The stamped steel front cover on the torque converter connects to the flexplate on the back of the Duramax engine with welded tabs that can twist and flex under load and distort the front cover. The most common problem areas for stock Allison transmissions are the clutch packs and the torque converter that do not hold up well under high loads especially with performance upgraded engines. While the GM engineers designed their “limp mode” to protect the truck we have found that by the time it engages in many cases that the damage has already been done and the truck will fall into “limp mode” more and more until it becomes completely undrivable.Unlike other diesel transmissions on the market the Allison has strong input, intermediate, and output shafts that generally hold up well even in some performance applications. But owners that push the performance envelope or work their truck hard may find that the transmission will not hold up to their expectations. The Allison 1000 transmission works well at stock performance levels for owners that do not demand a lot from their trucks, and let’s face it there are a lot of HD truck owners that do not tow, haul or use their trucks to the limits. WHAT’S WRONG WITH THE FACTORY ALLISON TRANSMISSION? This can lead to “limp mode” issues where the truck detects slippage and reduces performance to save itself from transmission self-destruction or even burnt clutches that can ultimately leave the truck stranded on the side of the road. But for owners that have made performance upgrades to their Duramax engines, work their trucks hard with heavy loads and strenuous towing demands or owners that compete with their trucks the stock Allison trans may not handle all that is demanded of it. In general use the Allison transmissions are great units with many satisfied owners out there using them happily. But a radical change happened with the 2020 model year Duramax trucks-the L5P diesel engine is now backed by a 10-speed Allison branded transmission built by GM. Starting with the 2017 L5P further changes to the torque converter and input shaft design reflected a slightly different 6-speed Allison configuration that was still in the Allison 1000 family. In 2007 GM also dropped the ZF6 manual transmission from the lineup offering only the Allison automatic trans in Duramax powered trucks.Īdditional refinements have been made along the production years through the LMM and LML Duramax era of 2007.5 through 2016 but they were basically all built on the same architecture. In 2006 the Allison backing the LBZ Duramax was enhanced with an additional overdrive gear, giving the now six-speed automatic even better fuel mileage along with TapShift gear selection driver controls. Additionally, the overdrive gear and lock-up torque converter worked together to deliver low RPM highway speeds while returning improved fuel efficiency. The smooth-shifting automatic proved to be a much more robust option to the automatic transmissions found in lighter duty trucks or even competitive brand heavy-duty offerings. WHY DO YOU NEED A "BUILT" ALLISON TRANSMISSION FOR YOUR HARD WORKING DURAMAX DIESEL PICKUP?In 2001 GM 2500 HD and 3500 HD pickups began offering the venerable 5-speed Allison 1000 automatic transmission backing the newly released LB7 and LLY Duramax turbo-diesel engines and optional with the 8.1L gas engines.
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