AISIN gear hunting in Cruise Control

[AH64ID]

Sitting around the campfire this weekend my dad mentioned that he ('17 3500 SRW AISIN) was getting a lot of gear hunting on his way to Yellowstone. At 65 it would go 6-5-4-5-6 rapidly, and not under heavy load. We talked about it for a few minutes and since I hadn't experienced that with my '18 he decided he would bring it up at his next service.

Well fast forward two days, yesterday, and I am towing home and experience it... often. I normally tow at 70 when able, but due to a 30 mph headwind I slowed back to 65. I locked 6th out with my ERS so I was only getting 5-4-5. The truck was not working that hard, ±40% load is where it happened every time. If the load didn't drop below 45% it would hold 5th as required.

This is only in cruise control, TH doesn't make any difference... I am fairly certain cruise control has it's own shift schedule aside from TH or non-TH but the AISIN programming isn't located on the ECM files I can view with UDC Pro.

Speed also made a difference. It would happen at 63-68, but I never had it happen above or below that.

Temp was 90-95°, and elevation was ± 5000'. GCW was likely 17,500. We weighed 18,150 on the way to YNP, but the water was empty and the beer was mostly gone on the way home.

So what's the deal? I've read some older threads on this subject and they all were for '16 and older trucks, and had a TSB released for them.

I plan to take it in and have it documented, thou they won't be able to recreate it.

It does tow like a dream thou! Aside from that crazy wind the mileage is within .5mpg of what my 05 did on the same trip, which I've done several times. That wind knocked my mileage down lower than I've ever seen thou, likely in the low 8's. I got out of the wind in time to get it back above an average of 9 I think, but won't know until I fill up the next time I drive it.

 

[CoastyAV8R]

Do all of the other tell tale signs of TH mode still work (IE, more aggressive downshifts, higher RPM shift points, etc)? When using the cruise in TH mine hunts around more than with it off but never has it tried to grab 4th at the speeds you mention unless I have it floored going uphill with a load on.

Driving back from Yellowstone last year to Central Oregon I almost ran out of fuel because of the headwinds we hit outside of Mountain Home, I was getting 7.5 mpg with a 30-35 mph headwind right on the nose. Truck drove great, you couldn't even tell it was working that hard other than the dogcrap fuel mileage.

 

[AH64ID]

Do all of the other tell tale signs of TH mode still work (IE, more aggressive downshifts, higher RPM shift points, etc)? When using the cruise in TH mine hunts around more than with it off but never has it tried to grab 4th at the speeds you mention unless I have it floored going uphill with a load on.

I haven't messed with TH off and cruise too much to see a difference in higher gears, but it does seem to have similar shift patterns in lower gears. I was driving around YNP using cruise to go from 45-35-25-45, etc. It was not as smooth the one day I was playing with TH.

Realistically you don't accelerate in CC like you do with the pedal, so it doesn't need full tables until higher gears.

I'm fairly certain it's 100% programming as dad's acts the same. Maybe I'll get lucky and a software update is already out.

Driving back from Yellowstone last year to Central Oregon I almost ran out of fuel because of the headwinds we hit outside of Mountain Home, I was getting 7.5 mpg with a 30-35 mph headwind right on the nose. Truck drove great, you couldn't even tell it was working that hard other than the dogcrap fuel mileage.

Yeah that was yesterday for me. It is impressive how seamless it was, other than a fuel gauge dropping rather fast. Added 12 expensive gallons in Carey, after filling in West Yellowstone and got home with the light on.

 

[brillmtb]

I have experienced the same thing, its irritating and I have to take the CC off at times. I feel like it is working the transmission too much.

 

[jetmechabq]

had mine to the dealership a couple of times now the first time they put the TCM in learn mode. the second time I had other problems but talked to the shop lead about it he call FCA (i know for the other and I think for the transmission) and was told the torque management has a very tight tolerance with the cruise on is it's 2 MPH. even with a no load my hunts at 60-70.

 

[jhenderson]

There’s a hill about a mile from my home. With the cruise set at 50 the truck downshifts from 5 to 4 every time. Holding 50 with my foot the truck never downshifts .

 

[AH64ID]

There’s a hill about a mile from my home. With the cruise set at 50 the truck downshifts from 5 to 4 every time. Holding 50 with my foot the truck never downshifts .

But does it hold 4th or go 5-4-5 in a matter of seconds?

had mine to the dealership a couple of times now the first time they put the TCM in learn mode. the second time I had other problems but talked to the shop lead about it he call FCA (i know for the other and I think for the transmission) and was told the torque management has a very tight tolerance with the cruise on is it's 2 MPH. even with a no load my hunts at 60-70.

I can't imagine it's torque management at 40% load, but who knows.

 

[jhenderson]

Shuttles back and forth for the 1/4 mile length of the hill.

 

[brillmtb]

Is it true that the Aisin is not programmable and does it learn? If it learns can someone not be able to create a program so you can tune and adjust the pressures, etc

 

[jetmechabq]

But does it hold 4th or go 5-4-5 in a matter of seconds?



I can't imagine it's torque management at 40% load, but who knows.

I get it with an empty load.

 

[Learjet]

I have had that happen too...only at the elevations you mentioned ~5,000' or so. I have never seen in do that 5-4-5...but yes 6-5-6 in a few seconds. Locking out 6th or turning CC off fixes the problem. Something in the programming makes it drop a gear early with the CC on vs. using the pedal.

FYI...36,000 total miles on my truck....and half of those miles are towing my 12,000 lbs. 5'er.

 

[RVTRKN]

Thats part of the 3:42 rear diff, I know, I'm ducking out of the way as I type this. That was a big complaint on the 2500 68rfe I drove. If you slow down the pressure is greater on the transmission to push it.

 

[Wiredawg]

I guess my 2017 Ram 5500 truck isn't representative of the situation described in this thread. As discussed in other threads, the Max Tow in the 5500 has special programming, my truck weighs 12.2K lbs solo, not sure how much the 4.88s play in it as well. I just never see gear hunting. In fact, this is the first truck I've owned that truly excels towing 21Klb 5er with cruise control on.

Is this mostly the 3.42 trucks experiencing this since they are running the lowest RPMs in 5th and 6th over drives? A 3.42 in double over drive is running right at max tq of engine (1800 rpm) at 70 mph? At 70 mph, I'm almost at my max HP of 2400 RPMs.

I actually changed ratios from 3.21 to 4.56 on my Jeep Wrangler because overdrive on the auto 5spd was right at the threshold of the transmission programming to hunt.

Sounds like y'all may need to lock out top overdrive on hilly terrain while in cruise control.

Cheers, Ron

Cheers, Ron

 

[AH64ID]

Thats part of the 3:42 rear diff, I know, I'm ducking out of the way as I type this. That was a big complaint on the 2500 68rfe I drove. If you slow down the pressure is greater on the transmission to push it.

Transmissions use TOS speed, load, and a couple other things to determine shifting but not gear ratio. It's a CC shift strategy issue at approx 40% load in 5th. Above or below 40% load and it works as it should, it's just sitting there that has issues... at least from what I've seen so far.

The same issue would be present at the given TOS, load, etc with 3.73's or 4.10's considering that gear ratio is likely not a factor in shifting strategy, and too much load is not a factor with this issue.

The TOS is about 2200-2400 for me to see the short shifting, with 3.73's it would be around 57-62 mph.

Hard part about you testing it is that we won't know if it's the gears or the new programming if you don't experience it.

I was very anti 3.42's for years, and have even priced 4.10 swaps... but after a couple thousand miles towing I am not convinced they would be better 95% of the time. The only time I think they would be better would be when I am pulling 8-12% grades at 10-25 mph, and while it happens a couple times a year it's less than 1% of my total miles and even then the trans just isn't getting too hot. On my 05 my biggest complaint about 3.73's was towing at 65-70, too many rpms in direct for hill pulling. 3.42's have fixed that issue, so in that regard I'm also much happier.

Is this mostly the 3.42 trucks experiencing this since they are running the lowest RPMs in 5th and 6th over drives? A 3.42 in double over drive is running right at max tq of engine (1800 rpm) at 70 mph? At 70 mph, I'm almost at my max HP of 2400 RPMs.

At 70 with 3.42's the rpms are 1570 in 6th and 1917 in 5th. I have not experienced the short shifting at this speed.

It does appear to be mostly 3.42 trucks, but I think we have more SRW Aisin's on this site than DRW's, so that will effect the sample base.

With your 4.88's you would have to be around 42-46 mph in 5th, and 40% load to get into the conditions experienced. At least where I have been towing that's not a common speed/load, so it's possible you're just not ever in the conditions to duplicate it.

Sounds like y'all may need to lock out top overdrive on hilly terrain while in cruise control.

It doesn't make a difference on 5-4-5 shifting.

 

[Wiredawg]

Transmissions use TOS speed, load, and a couple other things to determine shifting but not gear ratio. It's a CC shift strategy issue at approx 40% load in 5th. Above or below 40% load and it works as it should, it's just sitting there that has issues... at least from what I've seen so far.

The same issue would be present at the given TOS, load, etc with 3.73's or 4.10's considering that gear ratio is likely not a factor in shifting strategy, and too much load is not a factor with this issue.

The TOS is about 2200-2400 for me to see the short shifting, with 3.73's it would be around 57-62 mph.

Hard part about you testing it is that we won't know if it's the gears or the new programming if you don't experience it.

I was very anti 3.42's for years, and have even priced 4.10 swaps... but after a couple thousand miles towing I am not convinced they would be better 95% of the time. The only time I think they would be better would be when I am pulling 8-12% grades at 10-25 mph, and while it happens a couple times a year it's less than 1% of my total miles and even then the trans just isn't getting too hot. On my 05 my biggest complaint about 3.73's was towing at 65-70, too many rpms in direct for hill pulling. 3.42's have fixed that issue, so in that regard I'm also much happier.




At 70 with 3.42's the rpms are 1570 in 6th and 1917 in 5th. I have not experienced the short shifting at this speed.

It does appear to be mostly 3.42 trucks, but I think we have more SRW Aisin's on this site than DRW's, so that will effect the sample base.

With your 4.88's you would have to be around 42-46 mph in 5th, and 40% load to get into the conditions experienced. At least where I have been towing that's not a common speed/load, so it's possible you're just not ever in the conditions to duplicate it.



It doesn't make a difference on 5-4-5 shifting.

So, possibly lock out BOTH overdrives. Either way, still sounds like transmission is right at the LOAD threshold between 4th and 5th.

I really never play with my transmission, only time I ever locked out gears, was when I wanted to go SLOWER than the engine/transmission wanted to on steep downhill grade.

BTW, I see this on my wife's 2019 1500, 5.7V8 with 8spd transmission and 3.21 rear end. Its almost seamless, it doesn't bother me.

Anyway, I'm sure y'all will figure out a workaround OR just live with it and be happy.

Cheers, Ron

 

[AH64ID]

I talked to the dealership. He said he gets quite a few complaints on the issue, but without a MIL or software update there isn't much they can do.... which I agree with. FCA needs to publish a TSB with improved software. I think I'll file a case/complaint with FCA Customer Care, just to ensure they are aware of the issue.

So, possibly lock out BOTH overdrives. Either way, still sounds like transmission is right at the LOAD threshold between 4th and 5th.

That's the thing, it's not anywhere near a load threshold when it does this. 40% load is not too much for 5th, or any gear. It holds 5th until the mid 90's on load outside that shortshift window, or without CC. No real need to run around at 2300 rpms when 1800 has plenty of power.

It's a CC programming issue.

 

[Wiredawg]

I talked to the dealership. He said he gets quite a few complaints on the issue, but without a MIL or software update there isn't much they can do.... which I agree with. FCA needs to publish a TSB with improved software. I think I'll file a case/complaint with FCA Customer Care, just to ensure they are aware of the issue.



That's the thing, it's not anywhere near a load threshold when it does this. 40% load is not too much for 5th, or any gear. It holds 5th until the mid 90's on load outside that shortshift window, or without CC. No real need to run around at 2300 rpms when 1800 has plenty of power.

It's a CC programming issue.

I guess it's trying to find the happy word to identify WHICH sensor(s) inputs determine shifting. My point is numerically low rear ends seem to display this behavior, both diesel and gas, and variety of vehicles.

I haven't looked at the 2019 Aisin 2500 3500 SRW to see axle ratio options.

Anyway, hope y'all get a fix.

Cheers, Ron

 

[CoastyAV8R]

Unlike some others, I dont' drive my truck in TH if it's empty, I only use it when going up hills empty or when towing to alleviate the transmission shifting excessively. The truck doesn't seem to care as the transmission temps don't climb when it does hunt, it's just annyoying. Since it's not a "learn as you drive" transmission, short of a program update, it's not going to change so I adapt my driving habits to what I know it's going to do in certain situations.

 

[Wiredawg]

Unlike some others, I dont' drive my truck in TH if it's empty, I only use it when going up hills empty or when towing to alleviate the transmission shifting excessively. The truck doesn't seem to care as the transmission temps don't climb when it does hunt, it's just annyoying. Since it's not a "learn as you drive" transmission, short of a program update, it's not going to change so I adapt my driving habits to what I know it's going to do in certain situations.

It's not a learn as you drive, but IS listed as adaptive.

I only use TH when towing also. Just BLINDLY suggesting alternatives.

Cheers, Ron0

 

[Cummins2014]

It's not a learn as you drive, but IS listed as adaptive.

I only use TH when towing also. Just BLINDLY suggesting alternatives.

Cheers, Ron0

As far as gear hunting my 2014 68RFE will hold the gear climbing a grade with the foot on the pedal, but not in cruise . Same loaded unless of course the grade gets too steep.

As far as tow haul ,and EB, first things that get turned on as soon as the truck is started, nothing worse then going thru an area where I live at 40 mph in 5th gear, with the truck lugging along. With tow haul it holds 4th , much preferred over that feeling of lugging at that speed.

Any particular reason for not using tow haul when empty, and let it hold gears a bit longer ??