Allison Transmission Questions
Hello herbneffie,
Your next fluid change would be at two years or 23,000 miles whichever comes first since with Dexron III they lowered the interval to 18,000 miles from 25,000.I recommend Allison filters just from experience. I have seen some aftermarkets collapse and totally burn up the transmission. Have you considered synthetic Transynd? It costs double a normal Dexron service, but you have no time limits and can go 50,000 miles and just have the filters changed and an oil sample done. The fluid will not need to be changed until the oil sample comes back saying it needs changing. This usually means only one oil change for the life of your motorhome as long as you do the samples and filter only changes at every 50,000. It really is cost effective in the long run. I have seen a truck with 190,000 miles and original transynd, come back with ok readings (but the customer changed anyway, he figured he got his moneys worth)
As far as the harsh engaugement of downshifts while your exhaust brake is on, does it preselect 2nd or 4th? If it preselects 2nd when you let off the throttle, you should take it to your nearest Allison Distributor and have it set to 4th preselect. (I do it for free but I cannot say about other distributors) This takes about 5-10 minutes if you know where your DDL (computer plug) is. If it already preselects 4th, we can opt to change to 5th but not recomended at all because 5th is overdrive and you will pick up speed if you do not watch your speedometer.
Downshifts during exhaust brake function always seem a little harsher due to a higher calibrated shift. Stop and go harshness around town, try hitting the mode button. That should solve that problem.
I hope this answers your questions.