I am in desperate need of some help. I am currently in Northern Afghanistan deployed as an Air Force Civil Engineer.We have a 1984 cat 621 scraper here that we inherited from the SEABEES. we were told it was in working order but it will only shift into second gear. I checked my linkage and fluid levels but i am unsure of where to check next. i was wondering if there was somewhere to adjust fluid pressure or shift points? i am afraid to rip into it very deep because we have no gaskets here or even silicone to make some up with. Any help would be greatly appreciated. I also have a thread concerning trouble codes with a JCB loader on here if you have any advice on that. VR TSgt. Mitch Sisco United States Air Force
OK, I'll take a stab at it, but don't have my book with me. I've got the service manual at the house. By the way, I'm at BAF right now. I bet you're pretty close. First thing I would look at is the Trans Hold pedal in the floor of the cab. Make sure it's not activated, like maybe the shaft is rusty and hanging or clod of mud holding it down. 1st and 2nd gear are torque converter drive whereas the rest of the gears are direct drive so it would be able to shift in between those gears, but not past them. (I think I got the terminology right, but you see what I'm saying) Try that before you get carried away trying to adjust shift points. Have you had experience with 621's before now?
Start with the basics, Are all 4 brakes releasing? With the wheels chocked release the parking brake and make sure both shoes on each wheel move away from the drum. pull the front final drive plugs and see if there is any metal on the magnet. If the machine is not shifting and there is not a load from stopping it then you need to check some pressures. Do you have any gages? I rebuild five 621 for the Army SLEP program a few years ago. I have seen these machines inside and out but the trans were alway in perfect condition.
Now that I think about it some more, it might be smart to take the hose loose on that Trans Hold line at the transmission and put a little air tool oil or Marvel Mystery Oil in it.
One more thing, make sure the retarder lever is pushed away from the operator so it is off.
Make sure your engine is reving up all the way. Can you manually upshift it through the gears?
thanks for the help I tried the trans hold pedal traced it back to the tranny. it is getting air and the small shaft inside with the two rubber o-rings is able to move freely. with the pedal pushed it will not shift from first to second. when i release the pedal it shifts into second fine but then will not go any higher. i can not get into third no matter what i try. i even trid removing that small shaft from the trans lock and it still would not shift into 3rd. i do not have any guages here and only have limited tools available. i have not tried messing with the brakes any but it rolls freely when the parking brakes are off. the shift lever will flow through the gears freely and the linkage seems to be clicking into place but it seems like an internal problem that is keeping it from shifting. as far as 621 experience i am a relative newbie less than 200 hours in them. Thank you for your responses, i will keep monkeying with it. TSgt. Sisco
Try running it down a bit of a hill, it may be the RPM,s are not driving the whole machine to the shift point so you trick it by going down hill and gaining the ground speed required to get the engine up to the shift point, being the model it is i think the tranny is all hydraulically controlled, maybe some one somewhere did not want the machine going fast so they wound the allen keyed set screws right the wrong way to mechanically prevent the shift to happen, looking at the trans case from the rear there should be a series of female allen headed plugs just under where the top cover goes over the valve pack, the screws behind there are for setting shift points both up and down for various gears, really need a manual to work out which is for which gears. Another thing could be if the trans has been apart the tourque convertor could have all the rollers in the one way clutch ass about. Good luck!!
Is this your little baby? It was parked in Marmal some time ago. If i remember right all eq i found there where seabee stuff. And i realy wanted to take this one for a ride (Its not one scraper in Norway)
If I had a 621 book I would send it to you. What is wrong with our d--- government they can't supply you with what you need to get the job done with all of our tax money they p--- away on everything else. THANK YOU FOR YOUR SERVICE TO OUR COUNTRY!!!!!!!!!!!!!!!!!!!!
Problem Solved!!! I want to thank everyone for the help i ended up putting some oil in the hole that held the trans hold shaft. i let it sit all day and it is shifting now. a little rough but it works. I don't think it has been out of second gear for a long long time. The picture posted here is nearly identical to the ones i am running here. just a different color. Once again I thank you all very much. We just got in country so I am sure you will be seeing me on here again. VR TSgt. Mitch Sisco United States Air Force
Well done there Mitch, don't know much about scrapers don't have many of them here in Eire,but do keep in touch let us know how things are going. Stock