I have a 91 Safari Trek 2810 RV with Isuzu 4BDT 3.9L Turbo Diesel engine and a JAPCO 4 speed automatic transmission. . The transmission is no longer shifting into 4th gear and I have no waning lights on the dashboard. This problem started as an on and off issue about 3 months ago, but it has been an "On" issue for the last three weeks. I believe this is an electrical/Computer related issue rather than a bad transmission (it only has 50K). I changed the transmission fluid and filter 5K miles ago (a year ago). The "Economy" light will not light up when I turn it on (whether this light comes on, or not is my indicator whether the transmission is going to shift into final gear). Has anyone experienced this issue before and solved it? I would really appreciate any suggestions.Thanks a lot
91 Safari Trek 2810 Isuzu 3.9L Turbo...Austin, TX
I did double check both fuses, and they both were good. Where would "the grounds for the computer and harness" be located? I know where the ATCU you is, and I made sure the two plugs were plugged in tight going into it. The RV is devintely not shifting into 4th gear, I can't go faster than 45 mph. The "Economy" light won't come on either. I changed the inhibitor switch a year ago, because the RV was down-shifting on it's own when it was not supposed to...that took care of the problem. How do I know the model # of my transmission...is there an ID plate somewhere?
It is based on the NPR truck Chassis. It is a 4BD 1T, 3.9L Turbo diesel. I replaced the ATCU fuses and unplugged the battery for 1hr, still no go. I really feel the issue is a computer/Sensor or vacuum related issue, I do not believe the transmission has gone south.
Thanks for all your help Erik, I really appreciate it.
Thanks a million Erik, I'll start with that and hope that will do the trick. I also plan on changing the transmission fluid and filter. I read on the forum that I can unscrew one of the transmission lines going to the cooler and flush more transmission fluid that way...do you have any tips on how to do it safely?
You may find some useful troubleshooting help in the ATSG rebuild manual for the JR403E. The manual goes into detail with how the electronics work and how to troubleshoot all of it in and out of the tranny.
No problem Erik, I did find it...Thanks so much. You know I just drove back from town (without transmission oil...because no one had the gallon size from Valvoline). On the way, I started thinking about the exact symptoms. When i take off, it seems that I have to give the RV more fuel to get it rolling...it feels like I am not starting in first gear...it feels more like I'm starting in second gear. Another thing I noticed is the fact the "Economy" light does not come on when the RV does not go in 4th gear. My understanding is the Economy switch tells the Transmission not to shift in OD. if that is correct, then is it possible that I have a faulty "Economy" switch? Is there a way to test it?
A couple of questions on flushing the transmission fluid:
1- Is it best to drain before it goes into the cooler, or after it exits the cooler (return line)?
2- Do I need to have the RV in gear while I flush the transmission fluid?
3- I've been using Valvoline, is that what you would recommend?
Thanks again for all the hel from you and all the other good people on this forum.
Still won't **** into 4th gear/ I think it is what's know as "Fail Safe Mode"...I just don't know how I got there in the first place and how to get out of that mode, everything I've tried so far did notsolve the issue.