HandLogger
Well-Known Member
re: CAT 420D FDP08XXX (3,500+ running hours)
We're experiencing trouble shuttle-shifting into reverse. Sometimes it will shift into reverse at startup and sometimes it won't. Sometimes it shifts into reverse only after the machine has been used, which is why I used the word "intermittent" in the thread title. Either way, I have never experienced anything close to what I would call "clutch plate slippage" during operation (in either direction). The machine is typically used on steep terrain, so any clutch trouble should've been fairly easy to detect.
As the reverse alarm comes on each and every time the shuttle control is shifted into reverse, I removed the floor plate and took a look at the Shuttle Control Valve Group (SCVG) on top of the transmission. After voltage testing the two lines that send battery power to the forward and reverse solenoids, I found that the shuttle control seems to be functioning correctly, which lead me to believe that either the reverse solenoid or the internal directional spool in the valve assembly were defective. NOTE: The solenoids were more or less "stuck" to their respective shafts, so there was no way for me to swap them around.
So I ordered the SCVG and, in the meantime, took the opportunity to service the transmission by draining the fluid (which exhibited no signs of overheating), replacing the old filter with a new filter (CAT 471-7003) and inspecting the transmission suction screen for contamination. The suction screen did have some bits of matter stuck to it that were very soft an "slick" to the touch, but there wasn't a lot of it. It's also worth noting here that there were only minute traces of metal stuck the magnet on the back of the suction screen cover and, quite frankly, I've seen far worse in other transmissions. Regardless, the suction screen and the magnet were cleaned thoroughly and placed back into the transmission.
After receiving and installing the SCVG (CAT 223-8181), I added approximately 4 gallons of TDTO 30 Fluid (CAT 8T-9572) to the transmission, checked the fluid level and started up the machine. After letting the transmission warm up, I checked the fluid level again, using the warm oil level marks, and all was well. During this part of the work, the machine was shuttling between forward and reverse with no trouble. After moving the machine out of the repair area, however, the reverse issue returned.
Electronics being electronics, I suppose that the shuttle shift control assembly itself (on the steering column) could be intermittent...but I couldn't get it to fail when I initially tested it, so it doesn't seem likely. If anyone happens to know the CAT part number for the sealed shuttle shift control, I'd really appreciate the information.
By the way, all of this testing and troubleshooting was based on my past experience and information I found while researching CAT 420D issues on the internet (we don't own the manuals). As this machine has had what I would call a "comfortable" work life, I really think that having to rebuild the transmission at under 4,000 running hours is a bit premature...but, then again, I did find that slippery black matter stuck to the suction screen, so I can't be sure.
Please note that I've assisted auto transmission techs with rebuilds in the past, but I'm no tranny expert. This being the case, I haven't made any attempts to pressure test this issue and, quite honestly, I wouldn't really know how to approach that kind of testing when it comes to a CAT tranny. This machine has definitely been the most versatile machine we've ever owned, so any thoughts on this would be greatly appreciated.
EDIT: The metal placard riveted to the transmission has the CAT part number 192-0844 pressed into it.
Thank you kindly for your time ~ HL
We're experiencing trouble shuttle-shifting into reverse. Sometimes it will shift into reverse at startup and sometimes it won't. Sometimes it shifts into reverse only after the machine has been used, which is why I used the word "intermittent" in the thread title. Either way, I have never experienced anything close to what I would call "clutch plate slippage" during operation (in either direction). The machine is typically used on steep terrain, so any clutch trouble should've been fairly easy to detect.
As the reverse alarm comes on each and every time the shuttle control is shifted into reverse, I removed the floor plate and took a look at the Shuttle Control Valve Group (SCVG) on top of the transmission. After voltage testing the two lines that send battery power to the forward and reverse solenoids, I found that the shuttle control seems to be functioning correctly, which lead me to believe that either the reverse solenoid or the internal directional spool in the valve assembly were defective. NOTE: The solenoids were more or less "stuck" to their respective shafts, so there was no way for me to swap them around.
So I ordered the SCVG and, in the meantime, took the opportunity to service the transmission by draining the fluid (which exhibited no signs of overheating), replacing the old filter with a new filter (CAT 471-7003) and inspecting the transmission suction screen for contamination. The suction screen did have some bits of matter stuck to it that were very soft an "slick" to the touch, but there wasn't a lot of it. It's also worth noting here that there were only minute traces of metal stuck the magnet on the back of the suction screen cover and, quite frankly, I've seen far worse in other transmissions. Regardless, the suction screen and the magnet were cleaned thoroughly and placed back into the transmission.
After receiving and installing the SCVG (CAT 223-8181), I added approximately 4 gallons of TDTO 30 Fluid (CAT 8T-9572) to the transmission, checked the fluid level and started up the machine. After letting the transmission warm up, I checked the fluid level again, using the warm oil level marks, and all was well. During this part of the work, the machine was shuttling between forward and reverse with no trouble. After moving the machine out of the repair area, however, the reverse issue returned.
Electronics being electronics, I suppose that the shuttle shift control assembly itself (on the steering column) could be intermittent...but I couldn't get it to fail when I initially tested it, so it doesn't seem likely. If anyone happens to know the CAT part number for the sealed shuttle shift control, I'd really appreciate the information.
By the way, all of this testing and troubleshooting was based on my past experience and information I found while researching CAT 420D issues on the internet (we don't own the manuals). As this machine has had what I would call a "comfortable" work life, I really think that having to rebuild the transmission at under 4,000 running hours is a bit premature...but, then again, I did find that slippery black matter stuck to the suction screen, so I can't be sure.
Please note that I've assisted auto transmission techs with rebuilds in the past, but I'm no tranny expert. This being the case, I haven't made any attempts to pressure test this issue and, quite honestly, I wouldn't really know how to approach that kind of testing when it comes to a CAT tranny. This machine has definitely been the most versatile machine we've ever owned, so any thoughts on this would be greatly appreciated.
EDIT: The metal placard riveted to the transmission has the CAT part number 192-0844 pressed into it.
Thank you kindly for your time ~ HL