2/27/2024 0 Comments Firepunk 68rfe![]() The Revmax shop truck is also making big steam through a 68 but they haven't reached their 1000hp goal yet. RJP is the only one that comes to mind with 1,000+hp and big trap speeds with a built 68. I say this because there seems to be a ton of built 68s on this forum but very few people that actually have dyno and track time verified big horsepower(800+) going through them. I would also like to hear from people that had a built 68 that later swapped to a built 48, and why they did the swap? I'm probably going the built 68 route in the not too distant future but I'm still not 100% convinced they are performing for everybody as expected/hoped. What I would really like to see is a thread where everybody with a built motor and a built 68 could post their dyno numbers and track times. Or if the built 68 didn't perform as well as he had hoped and this made him want to swap. I was just wondering why he bought that if his original plan was to swap to a 48. Note it starts flickering just as we get to 16psi from 15psi.Understood, but the OP already has a Revmax 850 68rfe. The green line is attached to the TCM pressure switch wire. ![]() The graph shows line pressure in the 230psi range with a leakage into the OD circuit (orange) of about 16psi. It was then possible to replicate every run after that while the transmission was hot. To our surprise on only the fourth test the problem began rearing its head. Each time the transmission temperature would climb somewhat and we would continue repeating the tests until it was at least 200 degrees Fahrenheit in the transmission. ![]() To keep all equal, we held the truck at 2000RPM, 3rd gear, put between 200-240 wheel horsepower of load on it and held that for 1 minute intervals with brief cooldown periods in between. To best replicate the fault, we observed the conditions that caused a P0871 to set in a late model truck (that already had the anodized valve body) and recreated those on the dyno. Our sensors are wired into a high speed data logger that is also tapped into engine/TCM sensors. Analog gauges with rubber hose are far too inaccurate for this type of testing and length of rubber hose acts as an accumulator or buffer to the readings. Here we have modified a transmission oil pan to accept bulkhead fittings, installed pressure transducers (sensors) and connected very small nylon lines to the valve body to get accurate and fast response pressure readings. 1-The Solenoid Shift Valve (SSV) and 2-The Valve Body Separator Plate. Unlike its predecessor, the 48RE, the 68RFE is smarter and quickly identifies issues such as slipping or shifting problems, alerting you with a Check Engine. This means by the time you're setting P0871s, you've already been dragging the OD clutches.Ĭertainly there could be minor leaks from many areas, but our exhaustive testing shows there are only two areas we need to concentrate on to correct this leak. The 68RFE transmission, commonly found in 3/4 and 1-ton Dodge Ram diesel trucks, represents a significant advancement in automatic transmissions. Our experimentation shows this switch triggers at 16PSI, this just so happens to be right around the pressure required to apply the OD clutches (air check this if you don't believe us). This code is triggered when the pressure switch in the solenoid pack detects pressure in the circuit when it shouldn't be. Leaks into the OD circuit will cause the annoying P0871 code (set in 2nd or 3rd gear) but are also partially responsible for the burnt OD clutches we see on a daily basis. The caveat of increased line pressure is increased cross leaks, so it is important for us to correct these leaks when making a performance transmission. We, like most others, increase line pressure in our 68RFE transmissions to increase clutch holding capability. The most common cross leak observed with 68RFE transmissions is leakage into the overdrive (OD) hydraulic circuit this is in fact the only chronic cross leak area we see on 68RFEs. It is tribal knowledge among transmission builders that valve bores need to be inspected or vacuum checked and repaired and that flat surfaces need flat sanding to reduce cross leaks, but this "old wisdom" does not always result in a "fix" for newer transmissions. One of those is cross leaks in the valve body. Part One: The Valve BodyĪlthough cited as the weak link in the 2007 to present 6.7 Ram trucks, the 68RFE transmission can be a decent unit if you can correct some of its shortcomings.
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