Just returned from a 4800 mile trip down south pulling our 12,000 lb fifth wheel. We did the same trip last year. This year there were about a half dozen times where there was a very noticeable hard shift / clunk while towing. I'm not able to reproduce the hard shift and they seemed to happen at random. Didn't seem to matter if I was in tow haul mode or not. I was not able to determine if the truck was doing an upshift or downshift when the hard shifts occurred. I'm very close to the 30k mark and will be changing the fluid, but I have a hard time believing that has anything to do with it. Any thoughts?
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2021 3500 Aisin Occasional Hard Shift When Towing
- Thread starter roegs
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tchur1
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How fast were you going when the hard shifts happened? What was throttle input like when they occurred?
Speeds were probably 45 mph or less. Throttle would be light to medium. I drive with a soft to medium throttle - to be honest I'm not sure I've ever had it to the floor.
tchur1
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Im sure others will weigh in that are more knowledgeable about these transmissions than I, but I ask about speed because the AISIN is known to slip/clunk really hard when you are on the gas at slow speed, let off and coast, then get back on it quickly.
Ive had it happen a few times in my truck but almost always under 15 MPH so not sure thats what happened with yours.
H3LZSN1P3R
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Hard shifts do happen especially with the EB on when downshifting its no issue
I'm not sure if mine always happened during downshifts, but I did have the exhaust brake on during each rough shift occurrence.
I'd be curious to hear from others that tow heavy trailers - do you also experience some rough shifting?
Also, would there be a benefit to have the transmission set to relearn? I have some other service work at the dealership and could ask them to put it relearn mode when I leave.
H3LZSN1P3R
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I dont have the aisin but it could be worth the relearn
downsc123
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I get a somewhat hard shift going from 2nd to 3rd when towing my 14K GVWR 5th wheel RV. When not towing its very smooth - its not terrible but its more harsh than any other gear shift and it only happens on up-shift.
I can only recall clunky shifts when, as previously described, it's on off/on the go pedal - most notably for me during unexpected 2-1 downshifts then an abrupt upshift during rolling stops. I generally attribute most of that to my 2-foot driving habit and said rolling stops.
Yes, rolling stops will make the Aisin brain fart occasionally.
H3LZSN1P3R
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Even the stock non tuned 68rfe would stumble at times with rolling stops. Interesting to know the aisin does the same.
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From what I have seen on the forums the 19’s, and sometimes 20’s, are known for a harsh 2-1 downshift under certain conditions.
They all, even pre-19, seem to be prone to a hard 2-3 up shift when towing and worse in TH. It doesn’t always happen, nor does it happen at all throttle positions. My 18 and 22 both do it at moderate throttle. It’s not HARSH, but the harshest shift the transmission does.
They all, even pre-19, seem to be prone to a hard 2-3 up shift when towing and worse in TH. It doesn’t always happen, nor does it happen at all throttle positions. My 18 and 22 both do it at moderate throttle. It’s not HARSH, but the harshest shift the transmission does.
Isaacoakes
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Mine would clunk between the 1-2 shift and turned out they had to replace the valve body in the Aisin… Sounds similar to your issue.
Mine is a ‘21 3500 HO
Thanks for the note. Was your 1-2 shift problem when towing vs all the time?
Isaacoakes
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Wayyy more noticeable when towing.
Went to the dealer today. Turns out they did find a TSB related to my complaint. They installed 21-019-22 REV. A See PDF below for description. Turns out I'll be doing a short 20 mile tow with our 5th wheel today. While I'm not expecting to see anything during this short tow, I'm glad that they found the TSB. Reading through the document it appears to address a number of Aisin concerns. Once again, my local dealer gets an A+ for listening and working to address things I bring up.