Ken Thompson Posted January 8, 2023 Share Posted January 8, 2023 I recently replaced my ISC 350 with a newer, more powerful ISL 400 with the 2 stage jake. Since my Allison 3000 has never been programmed for a jake brake, it stays in 6th gear when I let off the throttle. I know most are programmed to shift to 4th, which is real abrupt. Some have them reprogrammed to only go to 5th. There is also a couple who like it to stay in 6th and they shift down manually. I know I don’t want it to shift to 4th, but can’t decide on 5th or leave it in 6th and do it manually. Are there any other parameters to set or change, like at what RPM it shifts down to the next gear? With everyone on here having traveled millions of miles, I know I can get the answer. Link to comment Share on other sites More sharing options...
Mark Holt Posted January 8, 2023 Share Posted January 8, 2023 The stay in 6th gear setting gives you the most control. If the Jake is not holding you at a safe speed on a hill simply apply brakes to drop the RPM to about 1400 and down shift to 5th. On my 45' Signature the Jake will hold me in 6th on most hills that I run into in the mountain west. Your lighter 36 coach with a 400 should do about the same. The Jake brake is far superior to exhaust brakes that many coaches have. Link to comment Share on other sites More sharing options...
Ivan K Posted January 8, 2023 Share Posted January 8, 2023 Mine drops to fourth but it won't do that unless it is in safe RPM range. I had a few emergency abrupt stops where I was glad it kicked in without manual intervention and yes, I definitely feel when it does, when at speed. Still did not stop me from totalling a pickup that wasn't supposed to be there, at 40 MPH. Maybe if I was in third or second at higher RPM. No way I could have done it manually. It's a personal choice. If you have time to downshift, your 6th gear would do fine but it is of course most effective on higher rpm. I have no idea about Alisson programing. Link to comment Share on other sites More sharing options...
willbo777 Posted January 8, 2023 Share Posted January 8, 2023 MIne drops to 4th as well, and I like it, of course after putting over 180,000 miles on it, I'm pretty used to it. And it will only downshift if at a proper rpm for the gear. Link to comment Share on other sites More sharing options...
Dr4Film Posted January 9, 2023 Share Posted January 9, 2023 Mine drops to 4th if my speed allows it to and then searches for 2nd once the speed allows the Allison to go into 2nd gear. That's what is displayed on my SilverLeaf VMSpc screen. I prefer that versus having to do it manually. Link to comment Share on other sites More sharing options...
Frank McElroy Posted January 9, 2023 Share Posted January 9, 2023 23 hours ago, Ken Thompson said: I recently replaced my ISC 350 with a newer, more powerful ISL 400 with the 2 stage jake. Since my Allison 3000 has never been programmed for a jake brake, it stays in 6th gear when I let off the throttle. I know most are programmed to shift to 4th, which is real abrupt. Some have them reprogrammed to only go to 5th. There is also a couple who like it to stay in 6th and they shift down manually. I know I don’t want it to shift to 4th, but can’t decide on 5th or leave it in 6th and do it manually. Are there any other parameters to set or change, like at what RPM it shifts down to the next gear? With everyone on here having traveled millions of miles, I know I can get the answer. Ken - Offline send me your email address and I'll send you screen shots of the Allison settings. You'll need the Allison software to change them. Personally I like the way Monaco configured the Jack brake Allison settings and most times low Jake is all I need going down a grade. Once you get below about 55 MPH the jack will not be very effective if you limit the downshift to 6th gear. The Jake needs engine RPM to work effectively in combination with the VGT in the braking mode. Don't worry about max engine RPM. The engine ECM won't allow the Allison to downshift if it will exceed the max engine RPM. That's assuming the engine ECM was programmed with the correct transmission gear ratios. Link to comment Share on other sites More sharing options...
Ken Thompson Posted January 9, 2023 Author Share Posted January 9, 2023 I know that going to 4th is real abrupt and revs really high when it hits. I assume not too high of rpm to hurt anything, but my brother in law had his changed from 4th to 5th and it made it a lot nicer. Once the jake is engaged, rather it be programmed to engage into 4th or 5th, does it still select the next lower gear at the same RPM as it would if programmed for 2nd gear? Will it slow down any faster when programmed for 2nd gear? I’m probably over thinking it. Link to comment Share on other sites More sharing options...
Frank McElroy Posted January 9, 2023 Share Posted January 9, 2023 Just now, Ken Thompson said: I know that going to 4th is real abrupt and revs really high when it hits. I assume not too high of rpm to hurt anything, but my brother in law had his changed from 4th to 5th and it made it a lot nicer. Once the jake is engaged, rather it be programmed to engage into 4th or 5th, does it still select the next lower gear at the same RPM as it would if programmed for 2nd gear? Will it slow down any faster when programmed for 2nd gear? I’m probably over thinking it. The down shifts are all controlled by the engine ECM to keep the RPM high but below the engine max rated RPM. So, when the Jake brake is turned on, the Jake brake solenoids are activated on either 3 (low jake) or all 6 (high Jake) cylinders on your ISL, the fuel feed is shut off, the VGT goes into an engine brake mode and the transmission is commanded to shift to 2nd gear. Now, down shifts are controlled by the engine ECM such that it only downshifts if the engine RPM wont exceed the Max engine RPM setting. Once below about 10 MPH, or if the throttle is pressed, the engine turns off the Jake brake. Link to comment Share on other sites More sharing options...
Tom Cherry Posted January 9, 2023 Share Posted January 9, 2023 32 minutes ago, Ken Thompson said: I know that going to 4th is real abrupt and revs really high when it hits. I assume not too high of rpm to hurt anything, but my brother in law had his changed from 4th to 5th and it made it a lot nicer. Once the jake is engaged, rather it be programmed to engage into 4th or 5th, does it still select the next lower gear at the same RPM as it would if programmed for 2nd gear? Will it slow down any faster when programmed for 2nd gear? I’m probably over thinking it. Maybe not and this sounds like a shade tree comment. I had my Allison serviced once and the shop totally drained and left the pan off for several hours. Per Allison, then the 19 QT was not sufficient for the refill. The shift pad electronic level showed 3 QT. Allison told me to only add one and then check….then add 1/2….until OL OK on the pad. That was in early 2018. Last year I noticed the Allison was abruptly downshifting when the VGT Exhaust Brake was turned on. That kept bugging me. I checked the oil level per the instructions and finally decided to experiment. I put in one QT. Still same OL OK. Did not get a high level. I drove it another 50 miles and it was better. So, I add 1/2 quart. BINGO….the sweet spot. I had 12 - 14 K on it since the service and did a NC to Southern CA to Seattle and home via Indiana run. I also did a couple of NC I 40 Black Mountain descents. When in CA, I went all the way into Sequoia and that is a pull up and a nightmare down. The Allison stayed above 200 but never above maybe 212…so it was not overheated… There is NO scientific or technological explanation…..other than the electronic oil level is not precise enough to know the exact fraction of a quart. I have NEVER seen any drips and there is not any oil in the engine coolant. So, with that disclaimer, if you start with a pint….drive it to get it mixed in and then use the Exhaust….see if there is a change. I think I am the only one here that might have done it….but it worked…. Link to comment Share on other sites More sharing options...
Ken Thompson Posted January 9, 2023 Author Share Posted January 9, 2023 Since the electronic display doesn’t have half qt display, I guess you could be high or low up to a qt. and not know. I would think that if it was that critical, they would put a more precise electronic level sensor in there. Mine did read 1 qt low when I brought it back from the engine swap since we had to change the rotor in the torque converter. I will experiment with that. Thanks Tom Link to comment Share on other sites More sharing options...
Tom Cherry Posted January 9, 2023 Share Posted January 9, 2023 1 hour ago, Ken Thompson said: Since the electronic display doesn’t have half qt display, I guess you could be high or low up to a qt. and not know. I would think that if it was that critical, they would put a more precise electronic level sensor in there. Mine did read 1 qt low when I brought it back from the engine swap since we had to change the rotor in the torque converter. I will experiment with that. Thanks Tom The electronic pad, at least on mine will give you Low (maybe HIGH or overfilled) increments as in 1, 2 or 3….I don’t know past 3 as that was what I had and the Allison Tech support said “don’t use 3 as an exact” amount and add ONE quart and then work up in half quart (pint) increments after that….so, I felt I was also low,,but the shift pad said NO.. Go figure…. Link to comment Share on other sites More sharing options...
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