I haven't figured out that part, yet. I'm working on the car still. Black and Blue Cab. I'm adding the Black part.
I'm sure you've checked it all, but between the thermostat switch, the timing control circuit, and the relay is it possible the solenoid is not getting the proper voltage at the right time to send to the modulator? I haven't found a reference for what that voltage would be, but from the diagrams I'm seeing, I think it should be battery voltage. Perhaps you could piggy back a voltage gauge up through the floor with a switch to see what it is showing and maybe turn off/on the voltage to the modulator valve. If it is getting the voltage properly, it would most likely be an internal adjustment which the transmission setup on the Checkers are reported to be something for an experienced Checker mechanic. Having the manuals for the exact setup would be a big help with that. They have any old cab companies around that might have manuals squirrelled away?
This is a very old list of resources from 30 years ago, so these may be rabbit holes, to fall down in search of the proper information about the transmission that is in the checker that @squirrel has. Everyone's results may vary greatly!
Unfortunately, the manual doesn't show up in the Seattle Public Library's catalog. I bought some old manuals at the SPL book sale in the early eighties. They were about 25 years old, so I assume that the SPL discarded the Checker manual quite a while ago.
Hmmm...I think you're confusing the TCS system with the kickdown system. The kickdown is a simple electric switch that sends power to the solenoid in the transmission. It works. The Transmission Controlled Spark system uses a pressure switch that tells if the transmission is in high gear, and controls the distributor vacuum advance, based on the 3rd switch, and engine temperature, to reduce NOx emissions in the engine. I don't know if it's working, but I will eventually make sure it's getting vacuum when I'm driving down the road. I might bypass it all, too.
You are correct as usual. I've been trying to do some decoding on my BMW X3 transmission and saw TCM in the diagram and thought transmission control module. I guess 70 is a little too old for one of those. I still think a light wired to the kickdown module might still shed some light on why it might be shifting too soon.
Not really, because it's pretty obvious when the KD is working, and when it's not working. The overall problem is that the shift points are too early, 1-2, 2-3, whether it's in KD or not. And messing with the modulator won't get them late enough. So, there must be something else wrong with it. And using the manual low to hide the problem, doesn't help very much, as there is no manual 2nd gear selection available. No worries, as long as it gets me to PA and back home, I can live with it. Then put a TH400 in it with a different engine, and that problem will be solved. I'll just get a bunch of new ones!
I wonder if you could fool it like we used to do with Fords Cruisamatic. Start in low, shift up so it shifts to 2nd then back to lo so it would stay in second.
Sounds like a bunch of fiddling. Wonder if there is a manual valve body at that point! https://forums.jag-lovers.com/t/bw12-auto-transmission-valve-body/382051 11 pages of talk. too long, didn't read. https://theamcforum.com/forum/borg-warner-m12-for-performance_topic41345_page1.html parts https://www.automaticchoice.es/Catalogo AC/Catalogue/bw12.pdf https://transmissionpartsonline.com...php?TransPartsOnline=BW12&TransPartsType=BW12 https://www.charlietranny.com/BW812 Parts For Sale.htm and https://www.checkerworld.org/library-service-manualls-2
no, and I don't want to watch it! I've taken apart a couple of the Ford version many years ago, no desire to do it again. This one doesn't seem to have the same control system. I was able to do that on the 55 Tbird I worked on years ago, so I know what you mean, but this one doesn't work the same. D2 gives you 2-3, D1 gives 1-2-3, L gives 1.
ok, things are just getting silly now. Cup holder, and a built in screen? What is this, a new car? (yes, there's also a backup camera attached to the screen)
You beat me to it. A checker cab with a tach that goes to 10k rpms, that must be a rare sight, hahahaha
How many young man's dreams have been squashed when their wiser friends pointed out that the part making their 9,000rpm small block was a tachometer 4-6-8 switch? Cheers, Harv
Squirrel, I forget but I think you are running straight water in the radiator. I have had good luck with running 100% white vinegar for long periods of time. Maybe that and your sock would clean things up faster?
I put antifreeze in it a while ago... I'll keep the sock in it until it seems to not be doing much, then take it out, and just let things happen as they may.
The Jalopy Journal
