Should have a 70 stamped on bottom of part 😎👍

 

Yes, I mentioned that. The new part number is still set to 70C (and stamped 70) so the part number change is for another reason.

 

Oops didn’t see that good post

 

I'll get one on order right away if it's going to take a while.. Thanks!!

 

I installed it and it seems to work fine. ATF temps are lower now. One installation tip - the bolt for the cooling line retainer plate is not centered between the two lines so you have to install it in the same orientation. You can mark one end with a sharpie so you know which way to reinstall it.

 

according to my parts guy, superseded again to 86774933 but is in stock.
I'll be ordering today and looking to see if it has the 70 on it..

 

I ordered 86774933 at the dealer per the TSB but 85585333 is the one I received. The guy at the parts counter confirmed it is the new part number. It does have the 70 stamped on it. Just driving around town I haven't seen trans temp go above 150F so it seems to be working fine. I'll know more on our first camping trip pulling our trailer . . . Last year, with the original bypass valve I was in the 190's when towing.

 

Why not use the aftermarket bypass kit from TransGo?

 

The TransGo kit completely deletes the bypass function, cooler flow is 100% all of the time. With the GM bypass valve with the new 70C setpoint you still have cooler bypass function which gives you better transmission warm up - reducing spin losses and improving fuel economy, especially in the winter. At 70 C (158 F) you get 100% cooler flow.

I just towed our travel trailer with the new 70C bypass valve and it worked great - trans temp was about 154F and it used to be low 190's. So, I got the expected 20C reduction in trans temp.

 

Not sure what state your in but I'm in Az and the summers are brutal on transmissions. I went with the full bypass since our winters (Buckeye, Az) anymore consist of maybe a few weeks of "cold" weather. My temps are in the 130-150 range normal driving depending on ambient temps. I haven't towed since doing the bypass but I plan to install an additional external cooler.

 

I'm in Michigan - it's a little cooler here. 🤣 I know what you mean about Arizona weather - I've done vehicle testing in AZ. On one trip we decided to climb Camelback Mountain, it got up to 114F that day. It was on July 13, 2003, during the July 12-16 heatwave. July 2003 is the hottest month on record for Phoenix. I initially had 128F listed - that was from some of my Death Valley vehicle testing . . . .

 

Humidity (dew point) is the key to those things working...or not. I have one in my garage and it actually keeps the temperature bearable in the summer so I can work on projects but man is it a sweatbox lol.

 

I don't remember when I did the 70*C tranny stat swap. All I know now is that in normal driving or highway cruising; 147*F seems to be the favorite number she like to run at. Stop and go around suburbia and traffic jams on the Interstates will get up in the the upper 160's/low 170's.

 

The TSB says 2016-18..is this the same part in my 2015 8 speed? Anyone answer that before I search through a bunch of posts...

 

Sorry, I just noticed you said 8-speed. My answer was for 2015 6-speed. The TSB is only for 6L80 (MYC) and 6L90 (MYD). I'm not sure if this is the same transmission bypass cooler as the 8-speed has.

----- This is answer for 6-speed -----
You have basically the same part except the tubing connections work differently. So, 85585333 wouldn't be a "drop-in" replacement. You have 2 choices - you can buy 85585333 and swap out the internals of the bypass valve or buy the TransGo kit and swap out the internals. If you use the 85585333 internals you will have temperature regulation at 70C setpoint; with the TransGo kit you completely delete transmission cooler bypass.

 

Is this also correct for a 15 with a 6 speed?

 

Yes, just cooling line attachment is different. See my post just above yours.

Your TBV should have quick disconnects for the cooling lines.

2016-2018 has a retaining plate for the cooling lines.

It's easy to double check - it's on left side of transmission just behind the bell housing.

Various YouTube videos say that you can swap out the internals if you get a new TBV and have the old version with quick disconnects.

 

My bad, I assumed you guys were referring to the 8 speed. Didn't realize the 6 speed had the same issues.

 

Anyone know if dealerships will (or have to) replace the original tcbv under this TSB if I can't get any symptoms to appear?

 

In the TSB, it says to replace the t-stat even if the customer's complaints cannot be duplicated. So... you could complain about something outlined in the TSB and they should replace the t-stat (even if that condition doesn't really exist).

 

Curious, would this TSB apply to a 2011 6L80 too?

 

There is a link to the tsb in the first post, with the specific years/models trucks it applies to. You are asking for someone to read it to you?

 

There is a link to the tsb in the first post, with the specific years/models trucks it applies to. You are asking for someone to read it to you?

No, I'm asking if a 2011 would benefit from this part change or if it even has a bypass. I can read just fine.

TSBs don't always address every year model. However, many earlier models will suffer from the same issues. This is especially true for recalls.

 

No, I'm asking if a 2011 would benefit from this part change or if it even has a bypass. I can read just fine.

TSBs don't always address every year model. However, many earlier models will suffer from the same issues. This is especially true for recalls.

They indicate what years/models the tsb applies to. Reading it would clearly tell you if your 2011 truck is covered by it.

 

They indicate what years/models the tsb applies to. Reading it would clearly tell you if your 2011 truck is covered by it.

I read it. I see the years.

Let me try to explain this to you, as you seem to have a bug up your bonnet.

I understand the TSB applies to various 2016-2021 models.

When did GM add a Temp Bypass Valve to the 6L80E? 2015? 2014? from what I've read.

I had a failure at 68k miles on a truck I bought with only 53k miles. I've read enough to know these transmissions are especially susceptible to heat. I want to extend the life of my transmission as long as possible. If a Temp bypass valve will extend the life of my 2011 then I want to add one if it's possible. Obviously GM knows there's a problem with the 6L80, otherwise they wouldn't still be tweaking it after over a decade of production. If upgrades will extend the life of mine, then I want to take advantage of them.

I'm asking for help, not a lecture.

 

I read it. I see the years.

Let me try to explain this to you, as you seem to have a bug up your bonnet.

I understand the TSB applies to various 2016-2021 models.

When did GM add a Temp Bypass Valve to the 6L80E? 2015? 2014? from what I've read.

I had a failure at 68k miles on a truck I bought with only 53k miles. I've read enough to know these transmissions are especially susceptible to heat. I want to extend the life of my transmission as long as possible. If a Temp bypass valve will extend the life of my 2011 then I want to add one if it's possible. Obviously GM knows there's a problem with the 6L80, otherwise they wouldn't still be tweaking it after over a decade of production. If upgrades will extend the life of mine, then I want to take advantage of them.

I'm asking for help, not a lecture.

You can find out quickly if your 6L80 has TBV. It is on the driver's side at the back end of the bellhousing - just follow the ATF cooling lines back to the transmission. Look at post #20 for some pictures I posted. That shows the 2 flavors. The earlier version uses clips to hold in the cooler lines. The newer version uses a retaining plate. The 85585333 TBV is the retaining plate design. If you have the older version with the clips you have 2 options - buy the 85585333 TBV and swap out the internals or buy a TBV delete kit. There are posts above discussing it and the pros/cons of each. It's an easy job - I did it in about 20 minutes in the driveway (I bought 85585333 and have 2016 with retaining plate so only swapped valve, no internals swap).

 

@jmbrad The t-stats started in 2014. Your 2011 has no restriction in the cooler lines and would not benefit from installing the t-stat.

 

@jmbrad The t-stats started in 2014. Your 2011 has no restriction in the cooler lines and would not benefit from installing the t-stat.

@RedSLEd is right, yours won't have TBV. Your ATF cooling lineset bolts to the back of the bellhousing directly - there is only a block. It looks like this - this is the side going into the transmission.

View attachment 961255

Thank you both.

I plan on towing an RV in the near future and I already had the larger cooler installed when I did the rebuild. Just covering the bases.

 

Thank you both.

I plan on towing an RV in the near future and I already had the larger cooler installed when I did the rebuild. Just covering the bases.

For us, switching to the 70C TBV worked great. Pulling our trailer (with 2016 K2XX 5.3L/6L80/3.42) we used to see just under 200F, now we see low 160F. So, right at 20C drop. Highest ambient so far was about 90F, trailer is 5310# curb weight.

 

For us, switching to the 70C TBV worked great. Pulling our trailer (with 2016 K2XX 5.3L/6L80/3.42) we used to see just under 200F, now we see low 160F. So, right at 20C drop. Highest ambient so far was about 90F, trailer is 5310# curb weight.

That's awesome. I wish my truck had 3.42 gearing. I have the loathsome 3.08. All I could find at the time. I'm still debating whether to keep the 2011 or go with a 3/4 ton with a 6.0 or maybe an 8.1 if I can find one. Or, I hate to admit, switch brands. Once bitten, twice shy. I was a loyal GM man for many years, over 35 of ownership to be exact. Never a time without at least one GM in the fleet. The 6L80E has me questioning my loyalty.

 

As long as you rebuilt it with quality stuff and follow the 'severe duty' schedule for fluid changes, etc., the trans should last you at least a couple hundred thousand miles.

 

3. Anyone know if theyre still using the same torque converts that like to blow up around 100k with their remans?

Yup, same JMBX converter.

Just had a reman installed under warranty on our Suburban w/90k miles. Dealer should have replaced the torque converter when it was acting up…but it didn’t throw any codes so they got to replace the entire tranny instead.

I’ll be replacing the torque converter on my own dime after I put around 60k miles on it.

I replaced the converter in my Silverado at 90k miles - no warranty - at the first sign of acting up and before it took the tranny out with it.

 

Yup, same JMBX converter.

I’ll be replacing the torque converter on my own dime after I put around 60k miles on it.

Well damn, but kinda figured. And ya I was thinking about dropping the pan at 2.5 year mark since the tranny has a 3yr/100k warranty. Seeing if there's a substantial amount of metal. If so, reinstalling the pan metal and all and dumping the old fluid back in her, taking it back to the dealer for a new one. If no or limited metal go ahead swap the filter put a pan with a plug back on and go ahead and swap the torque converter then. I've seen several posts of the converters going bad as early as 40k.

 

Yeah I recently had a GM reman tranny out in our Suburban under warranty.
I’m going to swap the torque converter at the first fluid change.

Overkill for sure, but I see it as cheap insurance.

 

Does the new TBV come with a new gasket? If not, does anyone have that part number?

 

No, it didn't. I reused the same gasket with no problems, 4,500 miles so far.

 

Does the new TBV come with a new gasket? If not, does anyone have that part number?

No, it does not. GM p/n is 23135703. Can also use Dorman p/n 66219.