Transmission slipping when warm

Hey guys - been lurking here for years and have done a ton of searching but still coming up empty.

On my 2015 4.0 truck I just recently experienced the transmission slipping/unable to shift out of 2nd or 3rd gear when the transmission gets warm. When cold, normal operation, but as soon as it warms up she just doesn’t want to shift.

I took it to my mechanic and his knee jerk was the transmission needs to be replaced, but without any check engine lights, I’m not so sure. Haven’t pulled the pan off to see if there is any metal (yet). Is there a change this is a shift solenoid without the check engine light being triggered?

Appreciate the help/direction (and yes I did read the massive threads on the trans for this truck, but I felt like it was reading WebMD and suddenly needed to just replace the whole thing)

 

How many miles?
Has the fluid ever been changed and have you checked the level?

Tjat may not fix it but it’s an easy first start before firing the parts cannon like your mechanic wants to do

 

Can you manually shift the transmission into another gear?

 

Most likely slipping due to wear. I would try a good quality A/T additive and see if it helps.

 

I guess they tried the additive yesterday and it didn’t help.

just seems odd to me that it would be excessive wear yet still shift fine when cold- but then again, I’m no mechanic, just a diy guy.

 

One more thing to add- started at the same time, was the lurch everyone complains about. Might have even been the precursor to the slipping/shifting issue by a couple of days.

not sure if that helps

 

I tried that, but it had no effect in getting out of 3rd and into 4th once the transmission was warmed up

 

I would start with a full transmission fluid replacement, either do 4 to 5 drain/fills (driving some in-between), or use the method that disconnects a cooler line to pump fluid out. Then you must verify the transmission temperature is within range before checking the fluid level, using the overflow drain plug on the transmission pan.

Add a container of the red Lube-Guard ATF additive when you do the transmission fluid replacement.

If Lube-Guard and all-new fluid set at the proper level doesn't fix your issue, then the valve body/solenoids would be the next thing to think about changing.

These transmissions are generally bulletproof, and can go several hundred thousand miles with just fluid changes and not abusing it.

ToolCat

 

Get a second opinion from a transmission shop.

 

There is a member here that is a transmission wizard. Hopefully he chimes in for you!

 

@jgedwardsv answering the Q's in post 2 would help us help you.

 

Good catch, thought I had (was responding from my phone earlier).

roughly 137k miles. I believe we serviced the transmission fluid around 60k. I haven't gotten the details on what was done yesterday yet, but it sounded like he did swap the fluid and put the additive in there (something no slip, can't recall). I believe he said today or tomorrow he was going to pull the pan off and take a look.

Luckily it's a family friend and his last objective is to just throw money at it.

 

This and replace trans filter, clean pan and magnets along with new gasket, easy job, not too expensive either, even with the full fluid replacement.

You mentioned a full fluid swap being done, if you’re able, find out if it was a complete fluid swap or just a drain and fill which is roughly 30% of the total capacity, maybe a bit more or possibly less.

Best of luck to you OP.

 

Have you checked the fluid level? That should be number one on your troubleshooting list.

 

Transmission issues on a 2015 with your mileage is suspect and unusual. My guess is the last time it was serviced, the procedure was not done correctly and they thought it was full when it wasn't. And maybe now you are just hitting that tipping point where level is down enough to show signs. I'd be surprised if a proper flush and fill didn't fix this issue.

 

Bingo

 

Ask your friend what was the temp of the fluid when he checked it.

If he says , “ how would I know that? “. Then we probably have found the problem.

 

Quick update for you guys, and I really appreciate the feedback and how quickly everyone has jumped in.

I just spoke with my guy, he ran some more tests, it's not slipping when cold as well after a full fluid change. After looking further, he's identified (through the computer) that solenoids B and D are both not working or throwing codes, so now we know where the issue likely is.

It'll be a few more days as he's digging into this on the side for me, but he did say if replacing the solenoids means pulling the whole thing apart he'll probably send me to a transmission shop he works with.

 

I believe it was the dealer who did it the last time, not my guy. I had them do service until around 80k, then I got tired of burning hours while waiting with 18 people involved in the process. Easier to just drop it to my guy in town and then pick it up later so I can keep working (and not look like a psycho pacing around the showroom floor on the phone with clients).

 

What were the fault codes that make you think the solenoids aren’t working. They are accessed by dropping the pan, not the whole trans