POWERSHIFT TRANNYS IN GENERAL: Beginning in 64, my work at Cat for 30+ years, included becoming acquainted with the PS tranny Industry. I did a little design work on some of Cat’s PS trannys. Over many years, the PS industry went thru a lot of trial and error.
J I CASE PS: With the 70 series, Case tried their hand at designing a 3-speed PS for their larger tractors. In short, Case tried to COMBINE the functions of the range-clutches with the functions of the master-clutch. In other word, the range-clutches also served as the master-clutch. Doing this is a significant PS design flaw.
The 70 series Case range-clutches were not massive enough to adequately take typical master-clutch abuses. Human operators, with their foot clutch and throttle, often find it convenient to cause a lot of master-clutch slippage---- combined with high torque from a lot of throttle. This situation, in turn, causes a lot of heat to be generated. Therefore, the master-clutch must be massive enough to absorb a lot of heat from slippage and still keep the master-clutch disc temperatures down.
As John S alluded to below, the Case PS tranny is subject to being damaged if the operator is not correctly instructed. Many operators choose to not want any instructions. I have many sad stories about Cat operators. We had a saying that Cats needed to be “idiot proof”. BUYING A USED TRACTOR: I think that buying most USED tractors, having a PS with an unknown history, is a risky investment. If one is faced with repairing a PS, we all know the cost may be very extensive. Also, if the reason for SELLING the tractor is unknown, that is also a caution flag. For the J I Case PS, how many CaseIH dealers have the knowhow and parts availability to repair the 70 series PS tranny!!!
My very limited experience, with a Case PS, is a farmer friend of mine bought a used 2470. The PS tranny’s shift characteristics soon went bad. The tractor would completely stop and then “jump off the ground to start going”. The range clutch modulation completely went away. I knew it was a modulation problem but I was generally clueless about how much work was involved to turn the wrenches and fix the Case PS clutch modulation issues. Watching the video posted here, the problem was likely related to what Case calls the “retarding valve”. A range-clutch disengagement must overlap (be time retarded) the engagement of the next range clutch.
The friend’s 2470 has now sets for several years. It will likely be sold to a used parts company (like Worthington Ag) when the grandson, with green blood, takes over the farm in the near future.
BACK TO THE 70 SERIES IN YOUR POSTS: Here is why my next field tractor would likely be a used 2290 with a manual tranny and rated very conservatively at about 130 HP for the massive 504T. I checked and the horsepower range between the 1070 and 1370 is 112hp to 158hp. I think the only 70 series models, in that HP range, that offered a manual tranny, was the 1070, 1170 and 1175. I believe the 2290 was an upgrade of the 1175 and also the biggest J I Case model to offer an optional manual tranny.
IF you are buying a tractor mainly for draw bar work in the field ------ IF you have mechanical savvy and the discipline to NOT operate the tractor ABOVE ITS RATED HP (no offense intended)------ there is an easy way to adds the two main functions of a PS to a tractor with a manual transmission.
I consider the two main PS functions in the field are (1) to not need to stop-and-shift, when pulling a tillage implement across the field, and (2) to not need to over-lug the engine to get across the field. The way I added both of these functions, to my 1170 with a mechanical transmission was to turn up the horse power at the injection pump----- but only use the extra HP in temporary tough spots.
For a turbo engine, the boost pressure is proportional to HP. (for a fixed rpm.) Therefore, a simple pressure gage, installed in the cab and plumbed into the intake manifold is all the hardware needed to add the power shift’s two main functions to a tractor with a mechanical transmission. I set my 1170 from its rated 122 HP up to 150 HP on a dyno about 40 years ago.
A dyno is useful to first set the engine at rated HP and to learn its boost pressure at its rated HP and rated speed. Then use a Sharpie to make a line at rated HP pressure on the face of the pressure gage. Consider any boost pressure over rated HP as “the yellow zone”. We are familiar with our vehicle’s tac having a yellow zone.
With the tractor still on the dyno, adjust the “torque screw” (as my older brother with a 190XT called it) to a reasonable higher HP setting. Only recently has the clutch in my 1170 at 5000hrs begin to slip in the “yellow zone”.