Low RPM Trans Slip? 8HP70

[16RamHemi]

Hey guys, i have a 14 1500 5.7 with the 8 speed 8hp70 trans. I have a low rpm slip that i cannot find any information or like symptoms. Its like slipping or riding the clutch in a manual. From a stop in first it does not do it. It is mostly when slowing down then getting back on the gas. it will slip up to about 1700 rpms then come back to 1500 and "engage/go". I can feel the truck "engage", its not violent or harsh, very light but can be felt. If the engine is tacked up it wont do it. I try to keep rpms up to avoid it or feather the throttle easily getting going. Other than that i dont have any issues (no issues going into any gear up/down, no slip when down shifting etc). I manually shift most of the time to keep out of low rpm situations. But sometimes it cannot be avoided.

Any ideas what would cause this? Solenoids? i do not have a trustworthy transmission place around me. especially one that will be experienced with these 8 speeds. I changed the trans fluid this summer (fluid level was correct). Truck has done this prior to fluid swap. Has not gotten worse, its very consistent. Will do it every time at low rpm.

 

[indept]

Sounds like it could be a torque converter locking issue.

 

[Tim Garceau]

Have you attempted a TCM reset/relearn?

 

[16RamHemi]

Have you attempted a TCM reset/relearn?

all i have done is unplugged battery for yhe weekend. then drove it easy for a couple days. nothing changed. if it were a manual i would say clutch. but not sure how an automatic would relate

 

[16RamHemi]

Sounds like it could be a torque converter locking issue.

does the torque converter lock everytime you accelerate? even very light on throttle to just get going? say creeping from 5 to 15mph in 2nd or 3rd gear in town level ground?

 

[indept]

Not sure on the exact lock points but I know it locks in lower gears and they typically unlock as you're stopping to prevent stalling. It used to be that trannys locked in high gear only but they're always looking to squeeze out that last 0.00001 mpg

 

[Tim Garceau]

all i have done is unplugged battery for yhe weekend. then drove it easy for a couple days. nothing changed. if it were a manual i would say clutch. but not sure how an automatic would relate

I recommend another reteach but driving more aggressive after. That slip or empty feel is the programming softening up the transition to make it feel like you’re driving a Bentley.

 

[huntergreen]

all i have done is unplugged battery for yhe weekend. then drove it easy for a couple days. nothing changed. if it were a manual i would say clutch. but not sure how an automatic would relate

I would have the dealer do a relearn on the trans and just drive normal. The trans should adapt to your style of driving.

 

[16RamHemi]

I recommend another reteach but driving more aggressive after. That slip or empty feel is the programming softening up the transition to make it feel like you’re driving a Bentley.

I would have the dealer do a relearn on the trans and just drive normal. The trans should adapt to your style of driving.

but why would the trans slip from say 1200 rpms to 1700 then down to 1500 where it engages?

 

[Tim Garceau]

Does it slip when manually shifting or in tow haul mode? Not going to lie, I don’t think I’ve ever been that soft on the throttle to shift down there. Maybe some eco diesel guys will chime in.

 

[Burla]

What is the miles and service history?

 

[16RamHemi]

Does it slip when manually shifting or in tow haul mode? Not going to lie, I don’t think I’ve ever been that soft on the throttle to shift down there. Maybe some eco diesel guys will chime in.

if i downshift it and keep rpms 2k or higher it doesnt happen. it happens when say im slowing down to make a turn and its in a gear that lands rpms in that 1200 to 1500 range. get on throttle and tach goes uo to around 1700 then down to 1500 and engaging. or when i go through main street in my town its 25mph. like any other town, people drive differently. some faster some slower. if i have to slow down to say 15 or 20 for a car the truck will stay in 3rd and be around 12/1300 rpm. get on the gas to speed back up and tach will go up to 1700 then back to 1500 where it will engage.

 

[16RamHemi]

What is the miles and service history?

pan / filter and fluid change this summer with proper procedure. no difference before and after. 77500 miles on truck. do not know history. word is dealer maintained. fluid did not smell burnt at all when i drained it.

i do have a random shudder sometimes when shifting 2 to 3. i feel like this is not associated with trans. feels more misfire like. but scanned truck and no codes. plugs done this summer too.

 

[Burla]

do you drive in tow haul? that keeps the rpm's up.

 

[16RamHemi]

do you drive in tow haul? that keeps the rpm's up.

no. i used to. i found that in th rpms would still be too low. i hate the stock shift patterns. thats why i manually shift it. would a bad torque converter do this? is there a trans pump that could be messing up fluid/line pressures? shift solenoid going?

 

[crash68]

but why would the trans slip from say 1200 rpms to 1700 then down to 1500 where it engages?

The increase in the rpms could be an intended shift "flare". Yes that's a thing they can do to make the gear engagement smoother. Sounds like this happens under a low load situation, if that gear was slipping it would happen under load also.

 

[Burla]

no. i used to. i found that in th rpms would still be too low. i hate the stock shift patterns. thats why i manually shift it. would a bad torque converter do this? is there a trans pump that could be messing up fluid/line pressures? shift solenoid going?

I haven't looked into the 8 speed that much because I don't have one. Maybe it's time to. I sure wish those boys that made that rfe video would do an 8 speed video. Maybe motor city mechanic has something up.

 

[guru1ofatl]

Is it setting any fault codes? Is it tuned?

 

[16RamHemi]

Is it setting any fault codes? Is it tuned?

none. no tune. catback and mopar cai are only "mods". i scanned it last week and no codes found

 

[guru1ofatl]

none. no tune. catback and mopar cai are only "mods". i scanned it last week and no codes found

Since there aren't any fault codes I would say that the problem probably isn't related to internal trans slippage or line pressure.
Converter is a possibility but I would think that this would set fault codes as well.

What scan tool are you using? Can it datalog?