2015 Yukon XL Denali with 6L80 MYC Transmission Shuddering

[Jenn & Chris Carter]

Hi all, I'm new here and hoping y'all will be able to help give me some direction.  I have a '15 Yukon XL Denali with the 6 speed MYC transmission and almost 140k miles, my transmission has begun shuddering when I'm driving between 25-35 miles an hour, does not seem to do this at really any other speeds.  I spoke with a dealer who said their suggestion is just to go ahead and replace the transmission, this feels a little extreme at this point since Im not having hard shifts etc.  I've owned the vehicle for the last year and put about 27k miles on it in a year.  I have no records of any previous transmission maintenance and the fluid looked good when we purchased it.  I know that dropping the pan is a pain in the neck, but I'm thinking that I need to change the filter since I have no idea how old it is.  Husband is out of town and I'm wanting to get this dealt with ASAP.  I'm pretty capable of doing a flush or dropping the pan if I have a good write up to follow, so any advice would be much appreciated.  Also, what fluid have y'all had good luck with?  Thanks, Jenn

Edited September 28, 2020 by Jenn & Chris Carter
typo

[George100]

I would start with scanning the vehicle first, see if any codes are there. Some Tranny codes do not light the check engine light. These are codes that will start with a P07.  Dropping the pan is  putting yourself on Occams razor, you might see something in there but the fresh fluid you put in will  probably give you more trouble down the road as it cleans  all the varnish of the internals. Normally i am one to change fluid but only at its interval, you do not have the history so you do not know when it was done. Good luck

[Jenn & Chris Carter]

18 hours ago, George100 said:

I would start with scanning the vehicle first, see if any codes are there. Some Tranny codes do not light the check engine light. These are codes that will start with a P07.  Dropping the pan is  putting yourself on Occams razor, you might see something in there but the fresh fluid you put in will  probably give you more trouble down the road as it cleans  all the varnish of the internals. Normally i am one to change fluid but only at its interval, you do not have the history so you do not know when it was done. Good luck

thanks, I'll definitely look into reading codes first, I hadn't thought of that

[Grumpy Bear]

https://www.lubegard.com/products/red/

 

Shudder is often a torque converter issue with the lock up clutch. Might not toss any codes. If a proper dose of Lubegard cures the issue then the clutch lining is getting pretty thin. When it gets thin enough it's metal on metal and metal through out the transmission. Thus your garage advising a rebuilt replacement. Catch it early enough at its a converter replacement and not the transmission. If you decide to go with a new converter then add the Lubegard from the start. It will slow the wear rate on a new converter clutch. 

[swathdiver]

On 9/28/2020 at 11:49 AM, Jenn & Chris Carter said:

Hi all, I'm new here and hoping y'all will be able to help give me some direction.  I have a '15 Yukon XL Denali with the 6 speed MYC transmission and almost 140k miles, my transmission has begun shuddering when I'm driving between 25-35 miles an hour, does not seem to do this at really any other speeds.  I spoke with a dealer who said their suggestion is just to go ahead and replace the transmission, this feels a little extreme at this point since Im not having hard shifts etc.  I've owned the vehicle for the last year and put about 27k miles on it in a year.  I have no records of any previous transmission maintenance and the fluid looked good when we purchased it.  I know that dropping the pan is a pain in the neck, but I'm thinking that I need to change the filter since I have no idea how old it is.  Husband is out of town and I'm wanting to get this dealt with ASAP.  I'm pretty capable of doing a flush or dropping the pan if I have a good write up to follow, so any advice would be much appreciated.  Also, what fluid have y'all had good luck with?  Thanks, Jenn

The transmission fluid should have been changed at least twice by now and getting ready for a third time, the fluid is shot and cannot do its job anymore.  If no internal codes, do the fluid exchange, don't drop the pan yet.  These are very reliable transmissions and the first thing to go bad in them is usually the solenoids which can be rebuilt on your kitchen table to for about $100 plus fluids.  Your symptoms are indicative of a converter clutch issue though, get some fresh clean fluid in there.  Grumpy as always provides great advice too which ought to be heeded.

[Jenn & Chris Carter]

thank you all for the advice.  Thought I'd give an update.  We could never find service records of fluid or filter changes for the transmission so we went ahead with a fluid exchange and new filter.  Shuddering at 30mph was still present so we added the lube guard shudder fix.  We never found specs on how much to add, so we used one at a time and drove for about 100 miles then added another tube until the shuddering stopped after 3 tubes.  It's been smooth as silk since then.