8hp70 heater bypass

hawsk99gt said:

Can you guys recommend a reputable TSTAT either 180 or 190?

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crazykid1994 said:

I’ve been running a stant 190 for quite a few years now with no issues. I’ll try to get the model on it

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hawsk99gt said:

If I went with a Stant 180 would I need to have it tuned? I found one on Amazon. But I am fine with a 192 TSAT. Just greedy to be cool.

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Wild one said:

180,but if it's a daily driver a 190 is probably the better choice on the stock tune.Do not remove the factory mechanical fan if you're not going to tune it. If you're seeing coolant temps between 195 and 200 after a decent drive on a hot day, i'd leave it alone Mike.

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Daniel Ortiz said:

Well Gents, I got @caulk04 ’s dream machine installed. It may be easier for the 2WD guys to pop in and out, but I wouldn’t want to do that too many more times in my life with the tools I have at my disposal.

Cracking open some of those bolts was tough and I had to squeeze a breaker bar in to get the front drive shaft bolts loosened:

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Also, torquing the bolts back to 85 ft/lbs against the locked 4WD was probably a mistake, as I thought I heard a noise like a torque wrench clicking but from somewhere near the right-side front axle. After that, I opted to use a pry bar to keep the axle from turning. I’ll have to go test 4WD to make sure I didn’t snap anything.

The transmission cable was not too bad, aside from the tight torx bolts that damaged my cheap T40 bit. But a quick trip to the hardware store had me set up with some nice new Craftsman torx bits, and they did nicely.

I think God Himself took pity on my feeble attempts to get the snap ring off with my crummy snap ring pliers. They get all kinds of bendy under full load:

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Somehow I got them to work without too much trouble, although getting it back on was especially tricky since I also had to keep the plug pressed in against its spring.

The plug itself came out with a hard pull with some sturdy pliers. The small amount of fluid came out into a drain pan (I wasn’t worried about that small amount). Upon inspection, the factory plug assembly didn’t seem broken in any way I could see. Here it is (on bottom), with the spare assembly I bought online as part of the whole thermal management unit (middle), and @caulk04 ’s part plus the brass end I initially got from RevMax, when I thought it might be a broken plastic end piece (top):

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One thing I did notice a difference in between my factory plug assembly and the spare was the metal pin. The factory pin is the same thickness throughout, but the spare gets thinner where it goes into the wax motor:

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In the end I used all the factory parts along with @caulk04 ’s plug, just like he said to do in the beginning. It ended up fitting better on the factory pin. I opted to not put the spare assembly in because it occurred to me, if that didn’t fix the problem, I would still have a hobbled truck right when I need to make some long holiday drives coming up soon, and this took long enough that I didn’t want to do it again before the trips.

After getting everything buttoned back up, I took it for a road test through some highway and country roads, getting it up to its new operating temperature of (apparently) around 150 F:

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After several stop-start-stops to get back to the highway and headed back into town, it got up to 154 F:

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But cruising back into town on the highway, it leveled out at 150 F again going about 75 mph. This speed at longer than five minutes would have certainly caused a spike previously at operating temperature, but it hung tight at 150 F the entire drive back into town of about 10 minutes. So that’s great.

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I’ll report back after I’ve made a long Texas holiday trip this Thanksgiving.

@Fritter I’m afraid there will be no root cause discovery for now on why I had the temp spikes with the factory plug assembly. Holiday trips were more important for this busy dad, and the transmission seems to be just fine except for the temperature. If I get frisky in the future, I may swap the spare plug in to see, but I wouldn’t hold my breath.

@Joe _S2013 the spare TMU I bought came with the plastic inlet tubes without O-rings, but you’re right I’ve seen a YouTube video where they replace leaking O-rings on them and they were metal. It looks like they stopped producing the metal ones in favor of the plastic tubes. Perhaps the plastic tubes fail less than the rubber O-rings were.

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@caulk04 , thank you again for your amazing part. It’s taken a load off of my mind, at least until the truck can throw a new curve ball at me later. I’ll also report after my next long trip to verify no problems.

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Daniel Ortiz said:

@caulk04, I simply bought the whole thermal management unit assembly here, so it's probably a newer production unit than what we find on any of our 4th gen trucks.

Here's the label on the unit they sent me. Interestingly, it's Canadian-made.

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Yeah, that pin seems particular. Even the RevMax guys didn't size the inner diameter of their brass plug end correctly, as neither my OE pin or the pin from the unit above would fit in the receptacle it was suppose to go into (another reason I didn't use it, sadly, because I would have liked to).

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