![]() ![]() The 68-RFE can be rebuilt with upgraded parts making it a great shifting transmission but it is limited because of the small clutch packs, gear sets, poor valve body design and shafts that make up the transmission. They then made a few parts in the 545-RFE transmission a little larger again to then be used behind the Cummins which eventually became the 68-RFE that we know today. Chrysler used this basic design and adapted it to be used behind their gas engines calling it the 545-RFE. The 68-RFE internals are actually larger versions of those found in a Dodge Caravan transmission that originally debuted in 1989. Even the transmission case is cheaply designed and must be reinforced with a large aluminum pan and transmission brace over the top to keep if from cracking in half. As a result, there are many elements that must be upgraded in this transmission to make it reliable and handle higher power levels. The 68-RFE transmission was clearly designed to be the least expensive to manufacture. The 68RFE's wait until 4th gear to lock the converter and when they do, they partially lock - or modulate - into lockup. Unfortunately, this is where all praise for the 68-RFE ends. The torque converter is a PWM design allowing for precise application of the converter clutch which provides a smooth shift. The 68-RFE transmission has a much better gear split between its 1st through 6th gears providing gear ratio change that is in fact very close to the Allison 1000 transmission. Although the 48-RE can be upgraded, it will always be limited by bands, case issues and only 4 gears! Once upgraded the general consensus on the street is each re-built 48-RE lasts for less miles than the one before! (The majority of our customers have gone through several) If you’re looking to tow a trailer or go for more horsepower, the 48-RE transmission is not the best transmission choice. The lock-up torque converter was added as an afterthought to the already outdated low-line pressure transmission making it difficult to control the application of the converter clutch providing unpleasant TCC shifts. The big jump into overdrive creates a large RPM drop into 4th gear making it somewhat unpleasant for towing. The first three gears of the 48-RE are spaced evenly while the 4th gear is a massive jump into overdrive. Utilizing bands, hydraulic throttle valves and governor pressure to control shift timing, the 48-RE transmission will never be a smooth shifting transmission or have the consistency of the newer designed transmissions. ![]() The 47- RH and the 48-RE continued to use very old technology that has been passed on for many years. The older automatic transmission dating from 1989 to 2002 when the 47 RH then the 48-RE transmissions were introduced were designed after the 727 Torqueflight Chrysler transmission and were never suited for the diesel market. WHY YOU WANT TO INSTALL AN ALLISON 5 OR 6 SPEED TRANSMISSION BEHIND YOUR 12V, 24V 5.9L OR 6.7L CUMMINS DIESEL ENGINE ![]()
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