C6 slow to go when cold

[grumpin]

It’s happened two or three times now, when cold and first start of the day, no go in drive or reverse.

Today I waited a bit longer, but no engagement. However both times when I put it down in first it engaged then worked as normal in drive and reverse.

Some research indicates that the front seal could be old and hard and it takes a bit to warm it up. Another idea is that the torque converter is draining and has to fill up.

But those two don’t make sense to me as putting it in first helps. I think tomorrow I’ll go straight to first gear and see what happens.

Anyone experience this on a C6 tranny?

[Gary Lewis]

I've not experienced exactly that.  In my case the tranny hadn't been used in a couple of years and it wouldn't go forward in D, but would in 1st.  And it was fine in R.  After usage it got better, but I put a bottle of Sea Foam in it and after a few miles it was fine.  I'm not sure if the Sea Foam did it or if just more usage did it.

How old is your fluid?

[Jacob84]

I’ve got more experience with this than I’d like to admit. I would say a seal is on its way out or old. When I first got my truck it sat for years so every seal was toast. I remember sitting in a parking lot for 15 mins waiting for it to go into drive. Once it did, I drove it home and got ready to pull the trans and got it rebuilt. It’s starting to do it again. It can sit overnight and it’ll take about 15 seconds for it build up enough pressure to move no matter what gear. Sometimes it works instantly, sometimes it doesn’t. It’s leaking out of the front seal as well. I’d almost put money on saying it’s a seal in your case.

[Gary Lewis]

If it is a seal then a temp fix might be a can of "seal sweller".  Many of the additive companies sell chemicals that are supposed to soften and swell the seals.

I've had some experience with them and they work - for a while.  But typically they are making up for worn out chemicals in the ATF.  Which is why I asked how new it is.

[grumpin]

Ok, thanks Gary and Jacob!

I don’t know how old the fluid is. I haven’t changed it since I got the truck in February of 2017. It has about 160,000 miles on the truck. Something always comes up. Want to change the tranny fluid in a few vehicles.

I’ll probably look into getting it rebuilt. We have an AAMCO here in town. And I’ve found a shop I like. So maybe time to get to know the AAMCO folks.

[86 1/2 Brutus]

I have this issue with Brutus when his tranny oil gets low.  has a leak at the main back seal, and it if gets just a little low, it does not want to shift into gear.  when you shift it, nothing, you give it a little gas and it starts to go.  

[Gary Lewis]

Dane - If you don't know how old the fluid is I'd have it changed and see what happens.

My SiL had a Jeep Cherokee that wouldn't back out of the driveway w/o lots of throttle and slippage.  We put a bottle of one of the name brand transmission fix/seal sweller stuff in and drove it a bit.  The next morning it backed right out of the driveway.

I told him it was a temp fix as the chemicals in the fluid were worn out and he needed to have the fluid changed.  Sure enough, in a month or so it started slipping again.  So he took it to a shop and they said if you change that fluid you'll ruin the tranny.  I said try another shop.  The next one said the same.  The third one changed it and he drove it for several years with no problems, but had to sell it when they moved to Nicaragua.

So I'd have your fluid changed.  Lots less expensive and lots easier than a rebuild.  And not expensive enough that if it doesn't work you've lost a lot of money.

[Jacob84]

I used some SeaFoam trans fix additive when mine started messing up the first time. Worked pretty good for awhile. Changing the fluid would be good thing to do too. While rebuilding a C6 isn’t that expensive, a transmission fluid and filter change is a ton cheaper. It might be the ticket.

Change the fluid and if everything else with the trans checks out- (band adjustment, vacuum modulator, fluid condition and level, any external adjustment you can think of checking whether it relates to the issue or not) and it is still giving you issues then you know what’s in your future. IMO it always pays to check everything you can and it’s free. That way you can rule out everything else.

But the fluid change can buy you some time or may fix it completely. Like Gary said, I would start there

[grumpin]

Thanks! I agree, as I thought about it last night, my thought was change the fluid and filter and add some Lucas Trans Fix.

I’m not a big “snake oil” fan by any means but have had luck with their power steering additive.

The fluid level is good, usually the first thing I check.

I’ve heard where folks say not to change the fluid, it’ll stir things loose and mess up the tranny. I don’t think that is right, IMHO, of course.

Woke up with a little snow on the ground, so hopefully we will get a few good weather days to tackle it.

[Gary Lewis]

Note that I didn't say "flush" it.  I do worry that doing so might dislodge things, but don't know that it will.  However, if you just drain the transmission and the converter you aren't going to dislodge much.  And changing the filter is a must as well.

Personally, I've vowed to NEVER pull the pan on one of these transmissions w/o installing a drain plug.  I've made a huge mess in pulling the pans over the years, so I want to be able to drain it before pulling the pan.  And for ~$14 delivered, this B&M one from Amazon looks good.

[Dorsai]

I've had a similar problem with my C6.  In my case the problem was that in cold weather, putting the transmission into drive (or any other forward gear, but not reverse) would require waiting 1-3 minutes for the transmission to eventually notice and engage.  I was told that the most likely cause of this was old seals.

EDIT: It was only the first shift of the day that was problematic.  Even hours later on the same day going into drive would be fine - it was only sitting overnight in the cold that the problem appeared.

However...as part of my prep work for the trip out to Skiatook in 2019 I decided to change my transmission fluid - it looked fine on the dipstick, but I knew that it was at least 10 years old.  After doing so (I dropped the pan and drained the torque converter, but did NOT flush the system) the problem appeared to go away - at the least I don't recall it happening this past winter.  The weather here in GA is only just now getting cool enough for the issue to reappear, so I'll be keeping an eye out this time around and will report back.

The short version of the above?  Change your transmission fluid, see if it helps.  I used Valvoline MAX fluid.

[grumpin]

Gary Lewis wrote

Note that I didn't say "flush" it.  I do worry that doing so might dislodge things, but don't know that it will.  However, if you just drain the transmission and the converter you aren't going to dislodge much.  And changing the filter is a must as well.

Personally, I've vowed to NEVER pull the pan on one of these transmissions w/o installing a drain plug.  I've made a huge mess in pulling the pans over the years, so I want to be able to drain it before pulling the pan.  And for ~$14 delivered, this B&M one from Amazon looks good.

I like your thoughts on the drain.

https://www.amazon.com/c6-transmission-pan/s?k=c6+transmission+pan

[grumpin]

Dorsai wrote

I've had a similar problem with my C6.  In my case the problem was that in cold weather, putting the transmission into drive (or any other forward gear, but not reverse) would require waiting 1-3 minutes for the transmission to eventually notice and engage.  I was told that the most likely cause of this was old seals.

EDIT: It was only the first shift of the day that was problematic.  Even hours later on the same day going into drive would be fine - it was only sitting overnight in the cold that the problem appeared.

However...as part of my prep work for the trip out to Skiatook in 2019 I decided to change my transmission fluid - it looked fine on the dipstick, but I knew that it was at least 10 years old.  After doing so (I dropped the pan and drained the torque converter, but did NOT flush the system) the problem appeared to go away - at the least I don't recall it happening this past winter.  The weather here in GA is only just now getting cool enough for the issue to reappear, so I'll be keeping an eye out this time around and will report back.

The short version of the above?  Change your transmission fluid, see if it helps.  I used Valvoline MAX fluid.

That sounds good, and as Gary and you did I won’t flush it.

This morning it went right into gear.

[grumpin]

Interestingly this morning it went right into gear, then I let the truck warm up for a bit, then it did not go into gear right away.

[Dorsai]

Dorsai wrote

The weather here in GA is only just now getting cool enough for the issue to reappear, so I'll be keeping an eye out this time around and will report back.

So...it was 28 degrees this morning when I got up, perfect time to check this out.

The verdict?  Went into forward gear perfectly.  In years past it could take anywhere from 1-3 minutes to start moving forward in sub-freezing temperatures, but today it got going with no difficulty.  

[Gary Lewis]

A C6 is a very sensitive transmission.  I think they can sense a lot of things.  I had one that wouldn't shift right so I pulled into O'Reilly's and bought a bottle of Sea Foam.  Walked out, laid it in the seat, and started it up.  The tranny never missed a beat after that.  

But I put the Sea Foam in anyway later that day.

[Dorsai]

In other words, buying a bottle of Sea Foam is analogous to Mom threatening the kids with cod liver oil?  I've heard worse theories.

[Gary Lewis]

Yep.  Works every time.  But I'm doubting your mother did that.  However, I'd bet your grandmother did.  Tell her hello for me.

[Dorsai]

You are correct...Mom never did.  I'm sure my grandmother did to her children, but not to me; as a proper grandmother, her grandchildren ate whatever they wanted.

She asked me last week if you were still doing truck shows - she was disappointed this year's didn't happen, but of course understands why.  I told her I was going to try to make the next one, she thought that was a good idea. I'll tell her you said hi.

[grumpin]

Good to hear, the tranny that is.

Getting some warmer weather for this time of year so maybe I’ll get the tranny serviced this week or next.