Brand new TBV 70⁰ strange temps

mikeyk101 · May 17

So 2 months ago, my transmission failed. The dealership installed an OEM remanufactured one. They told me that they also flushed the lines to the condenser as well as installed a brand new bypass valve on those lines.

I know about 2 years ago GM came out with the 70⁰ updated ones and those clearly had 70 stamped into the base. This one does not have that.

I had installed one of the updated tbv valves right around when they first came out so I have some experience monitoring the transmission temps. The trans temps now have been a bit warmer than what I'm used to.

The old new one usually ran a pretty steady mid 140-150⁰ when driving long steady speeds. Now, the regular steady is around 155⁰. Outside ambient temp was around 75⁰. In stop and go city driving, the old new would creep up to mid 160 to sometimes around mid 170⁰ but usually came down in a reasonable time once back to steady driving. Today, the new one actually crept up past 190⁰ in the stop and go. Once back on highway driving steady speeds, it slowly started dropping but took almost a 1/2 hour to get under 170.

This doesn't seem right. I noticed the temps soon after reman trans was installed and driving back to Wisconsin from central Alabama. When the temps went up in stop and go, they took forever to get back down to "normal" but we're still mid 150's.

The day I got back, I set an appt at my regular dealership for an oil change and brought this up. I was told it's completely normal and temps will go up in stop and go. I tried to explain that I knew that but had already been driving with a 70⁰ updated version and had a different experience. I was told I would need to bring it back another day as it was late and the tech was already gone.

I hate to bring it in and pay diagnostic fee for them to tell me it's normal. My fear is that there is some kind of blockage that allows some fluid to pass to condenser and back but at a reduced flow. I'm wondering if it could be some metal shavings that got through when the original trans failed.

I did pop off the grill today to check the fins in the condenser. There was some dead bugs and crap but IMHO, not nearly enough to reduce flow for cooling. I did run a hose over the fine and make sure they were cleaned out.

So does anyone other than @GMCustomerService have any suggestions? I'm tempted to take off the TBV and do the pill flip. That would probably tell me if the TBV is working correctly. My only concern would be like I mentioned above, possible metal shavings in the cooling lines and that they may work themselves back into the trans which wouldn't be too good...

rav3 · May 17

If it were me, I'd do the pill flip & see what changes. Imo, heat kills transmissions. Getting rid of the TTC allows the transmission to run 'normal' just like the older 4L80 did. The only reason the TTC was added was pushed due to regulations from EPA. That's my opinion & I'm sticking to it. lol

mikeyk101 · May 18

Well it's easy enough to do it. I have some free time tomorrow and will get to it.

And I agree with you. Thanks.

newdude · May 18

1 hour ago, mikeyk101 said:

So 2 months ago, my transmission failed. The dealership installed an OEM remanufactured one. They told me that they also flushed the lines to the condenser as well as installed a brand new bypass valve on those lines.

I know about 2 years ago GM came out with the 70⁰ updated ones and those clearly had 70 stamped into the base. This one does not have that.

I had installed one of the updated tbv valves right around when they first came out so I have some experience monitoring the transmission temps. The trans temps now have been a bit warmer than what I'm used to.

The old new one usually ran a pretty steady mid 140-150⁰ when driving long steady speeds. Now, the regular steady is around 155⁰. Outside ambient temp was around 75⁰. In stop and go city driving, the old new would creep up to mid 160 to sometimes around mid 170⁰ but usually came down in a reasonable time once back to steady driving. Today, the new one actually crept up past 190⁰ in the stop and go. Once back on highway driving steady speeds, it slowly started dropping but took almost a 1/2 hour to get under 170.

This doesn't seem right. I noticed the temps soon after reman trans was installed and driving back to Wisconsin from central Alabama. When the temps went up in stop and go, they took forever to get back down to "normal" but we're still mid 150's.

The day I got back, I set an appt at my regular dealership for an oil change and brought this up. I was told it's completely normal and temps will go up in stop and go. I tried to explain that I knew that but had already been driving with a 70⁰ updated version and had a different experience. I was told I would need to bring it back another day as it was late and the tech was already gone.

I hate to bring it in and pay diagnostic fee for them to tell me it's normal. My fear is that there is some kind of blockage that allows some fluid to pass to condenser and back but at a reduced flow. I'm wondering if it could be some metal shavings that got through when the original trans failed.

The new valve doesn't have the "70" stamped into it? I can check one tomorrow on the shelf and see if its stamped. Pretty sure they are still stamping them.

Before your transmission failed, did you already have the updated TBV installed?

Also, driver's side of the radiator, do you have transmission lines going through there, or does the driver's side of the radiator have no fittings in it?

mikeyk101 · May 18

5 minutes ago, newdude said:

The new valve doesn't have the "70" stamped into it? I can check one tomorrow on the shelf and see if its stamped. Pretty sure they are still stamping them.

Before your transmission failed, did you already have the updated TBV installed?

Also, driver's side of the radiator, do you have transmission lines going through there, or does the driver's side of the radiator have no fittings in it?

I know my original updated replacement 2 years ago definitely had 70 stamped into it. So I know they definitely didn't reuse the one that was on the failed transmission. I saw a recent thread within the last few months though where another member had a dealership install an updated one and that was not stamped but was a 70⁰ TBV. I know that there is an updated part number also which he had. And based on the temps I am seeing, especially when running down the highway (155 or so) it does appear to be the updated TBV. When I had the original OEM one, it would get up to 190ish while running down the highway.

And yes, I had put the updated TBV on myself about 2 years ago, well before my transmission failed.

Mine is a 2016. I can see both transmission cooling lines and they both go from below engine on drivers side over to passenger side where they connect directly to condenser. And the transmission cooling lines are fairly new and were replaced last year when dealership discovered they were leaking. Also long before the transmission took a dump.

mikeyk101 · May 18

Ok, I found the thread and here is the post that details what the dealer told this member. He said dealer states they are bo longer stamping the 70 into the most recent version of the TBV.

And what he was experiencing is pretty close to mine. He was told his updated TBV that he had dealer install was defective and they installed another. His newest TBV sounds like it's now running as it should.

mikeyk101 · May 19

I pulled out the receipt from dealership to verify what parts were replaced and it only showed the reman transmission and 12 qts of Dexron fluid. I'm not entirely convinced they replaced the TBV.

I did climb under truck to remove the TBV and on closer inspection it was stamped with 70 on it but was very faint. I had to look close to see it.. For the most part, it seemed new but had quite a bit of grime on the cap that gets removed to flip pill. That part is normally hidden as it faces up. I'm thinking they just reused mine. When I look at diagrams if the transmission online, it doesn't show a TBV attached but only the space where it gets installed.

But I did get the pill flipped and the TBV reinstalled. And this time unlike 2 years ago, I made sure to verify that each cooling line had the required O-ring on it. That was a complete mess...

I didn't really have anywhere to drive to today but have a bunch to do tomorrow so I should be able to see if this does the truck. Probably about 70 miles of highway and about 25 miles of stop and go.

I will update once I have more results...

Edited May 19 by mikeyk101

Homewrecker007 · May 19

My 2018 had the transmission changed before I bought it, and the dealership did not change the TBV. Also refused to do it even with the TSB stating the issue. Then told me it was $285 just for the part. I ordered the $30 bypass valve and changed it out myself.

mikeyk101 · May 19

1 hour ago, Homewrecker007 said:

My 2018 had the transmission changed before I bought it, and the dealership did not change the TBV. Also refused to do it even with the TSB stating the issue. Then told me it was $285 just for the part. I ordered the $30 bypass valve and changed it out myself.

I may just end up doing that again myself. I'm just curious as to why I would suddenly seem to be having the temperature issues if this was the 70c TBV I had previously updated on my own. Is it possible that the transmission failing could have caused some damage? I didn't notice anything unusual on the inside components.

If the pill flip shows much lower temperatures, I will probably end up buying a new TBV and installing it sometime later this year. I do know that several regulars here say just doing the pull flip is enough but I would feel more comfortable having the updated TBV installed.

mikeyk101 · May 19

Something is definitely going on. Even with pill flip, temps rose to 161⁰ after over 1/2 hour of driving 75mph. One thing was it did take longer for the temp to rise. It stayed in mid to upper 150's while using cruise for first 20 mins or so of highway speeds but after turning that off, it went above 160. Last couple highway miles, it started dropping but never went below high 150's. Once off highway in 1 mile of stop and go, it reached 167.

I will be heading back home in about 2 hours. It will be several miles of stop and go and another 40 or so miles down highway. I will update after that.

I'm very surprised as the pill flip should have resulted in lower temps. I'm still wondering if there is some kind of blockage in cooling lines or condenser. Any idea on how I could check that?

mikeyk101 · May 19

Drive home... Started off in city traffic after truck cooled off for hour and a half. 9 miles of city driving. Outside temperature is right around 75⁰. Trans temp got to upper 170's. Then 26 miles of highway driving at between 75-80 and temp dropped but bounced between lower and mid 160's. Finally 25 miles of 2 lane back roads with occasional stop sign, traffic signal and roundabouts. Speeds of around 55-60mph. Temp ran mostly mid 160's but never dropped below 162 and got as high as 177 at one point.

I know on the positive that these temps are still below the old normal of mid 190 but still higher than I feel they should be. And especially after doing the pill flip mod, they are much higher than they should be.

Based on last discussion at dealership when I got oil change, I'm pretty sure they will tell me that these are normal but I know they are not. Not sure what to do next. I did check trans fluid level and it's fine. It doesn't smell burnt.

mikeyk101 · May 19

Now I've started down the rabbit hole and wonder if I got the correct replacement transmission. There are 3 possible choices.

1. 19431764

Description:
Sierra, silverado. 4wd. 5.3l. Exc.Heavy Duty Towing Package. Tahoe. 6 speed trans. All. Without towing package. Yukon. 5.3l. 6 speed trans. Suburban. 5.3l. 4wd. Yukon XL. 6.2l. Without denali. 4wd. 6 spd trans. Without enhanced towing.

2. 19431766

Description:
Heavy Duty Towing Package. Sierra, silverado. 4wd. 5.3l. Suburban. 5.3l. 4wd. With towing package. All. Tahoe. 6 speed trans. 4wd. Yukon. 5.3l. 6 speed trans. 4wd. Yukon XL. 6.2l. Without denali. 4wd. 6 spd trans. With enhanced towing.

3. 24279588

Description:

Sierra, silverado. 4wd. 5.3l. With enhanced towing pkg. Escalade ESV. 8 spd trans. Sierra, silverado. 4wd. 6.2l. Yukon XL. 6.2l. Exc.code-6u3l,6u8l. Yukon. 6.2l. 6 speed trans. With denali. 4wd.

On mine, I don't have heavy duty towing but I do have the Z82 "Trailering Package" which includes the auto locking rear differential. I also have the 3.42 gears. I am confused between Trailering Package and Towing Package. I know I don't have a Heavy Duty Tow Package but would I have what could be considered enhanced towing package? The reason I ask is because the reman trans that got installed specifically says "Exc.Heavy Duty Towing Package" as well as "Without towing package". I would have thought the Z82 Trailering might be considered the enhanced towing????

Now I'm concerned that I may have issues when towing my toy hauler camper. It comes in around 6200lbs loaded...

Edited May 19 by mikeyk101

Homewrecker007 · May 20

My 14 with the updated thermostat ran around 160° to work and it was 82° outside. Temps according to my Autosync.

mikeyk101 · May 20

23 minutes ago, Homewrecker007 said:

My 14 with the updated thermostat ran around 160° to work and it was 82° outside. Temps according to my Autosync.

Maybe I just need to ignore it. It's just odd because I had been using the updated 70⁰ TBV for almost 2 years and the temps ran lower than what I'm seeing on this reman transmission. And the biggest thing is that I did the pill flip yesterday and most folks I have read threads on claim dramatically lower temps but in my case, it didn't seem to do anything. Temps are almost the same as running the TBV in normal configuration.

Just to add, I have a BAFX Bluetooth OBDII device to monitor various vehicle functions. That is what I use to monitor the trans temp among other things.

Edited May 20 by mikeyk101
More info

Homewrecker007 · May 20

This is what I put in my 2018. I don't remember exact temperatures it runs at. I have not drove it since October. I do remember pulling my model A around in September it was running 170°

Edited May 20 by Homewrecker007