4l80e temp gauge through OBD scanner?

[stutaeng]

Doing some more research alot of guys say they put a sending unit in the pressure test port above the PRDNL switch, anybody have any experience with this? Some say it wont get an accurate reading, some say it may do some witch craft, most say it works fine, alot of them just say to be careful about the length of your sending unit because you can go to deep, they say measure your depth with something (Allen wrench or something) and compare it to your sending unit, or use that magnetic measuring crap on the end and gently thread it in and check how much is left.

Most recommend a shorter sending unit like this

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What do you guys think? Any objections? I don't see why not? I mean currently its just a bung in the side of the trans now, I'm basically just putting a shinier bung with a wire on the end in instead? Don't see what voodoo magic it could possibly do to the trans as long as it doesn't bottom out? To me it should also read fairly accurately I mean fluid obviously flows past it if it's a pressure testing port, and it's fluid that is flowing within the trans so it should be a fairly accurate temp I would think? Then again what do I know I'm just a shade tree mechanic haha.

I don't think that would be a problem. I'm pretty sure that pressure port should see fluid directly from the pump. On the 2 photos with the red arrow is where that threaded port goes into the hydraulic circuit.

I had to hookup a pressure guage to a unit I was diagnosing and had a super hard time getting the fitting on the threads. I had to temporarily remove the NSS to get to it and a put the little angle from the guage kit. I think for future hookup I was thinking leaving the angle and putting a nipple with a cap. Just an FYI to consider.

Let us know how it works out for you.

 

[PlayingWithTBI]

FWIU that test port is not in the stream/flow of the system, it's static so, you'll get delayed temp responses. As in the 3rd picture, you can see it's at the end of a passage.

 

[Duallylife]

Even if it's "static" it's still inside the "hot" trans, getting heat soaked from the surrounding metal and fluid around it, so wouldn't it still be about the same temp? Atleast within a few degrees. If it's to test pressure would there not be atleast some fluid flow? I mean I'm no expert by any means but anything has to be better than no gauge? I mean it should be enough to see if it's running right near the edge or atleast see some temp spikes? I mean It might not show right away, but if I'm pulling a big hill and by the top I see it climbed close to the danger zone atleast I'll know I need a bigger cooler or to be more gentle?

I say this because I have a trip coming up in 2 weeks, I'll be towing about 8k. I have towed this weight many times before, but lately it's been smelling like hot trans and my engine temp gauge has been riding a few degrees higher then normal. Making me think the trans is getting "hot" for some reason, and "driving up" my "engine" temp, because it's heating up the factory cooler making my rad hotter.

 

[L31MaxExpress]

TunerProRT on my laptop, matching ADS file for engine or transmission datastream and a USB to ALDL cable work great. GM OBD1 datastream apits out alot of information, especially on the later ones.

 

[PlayingWithTBI]

If it's to test pressure would there not be atleast some fluid flow?

Nope, it's still static, unless your gauge leaks.

I mean I'm no expert by any means but anything has to be better than no gauge?

Not if it's misleading. Then it'll be worse than no gauge - just saying

I'd rather have it in the pan or put a "T" in the line going to your aux trans cooler?

 

[Duallylife]

I hate in-line gauges, everyone I have done, or seen always leaks to some degree, or leaks at some point. I also hate them because no matter where I find they always end up corroded and rotting off within a year or two, or have issues. I also find that they don't read as accurate as the oil has time to cool, especily if it's T-d off the aux lines because it will have gone through the rad. I don't want to know what the oil is going back in, never believed in that and my trans guy said the same. I want to know what my oil in the trans is thats where the damage wil be, if its hot obviously my cooler isn't working. I'm also leery about in the pan because this truck is a plow truck, so it does go through alot of snow and slush, I would be afraid of it getting tugged, alot of times I'm either driving through snow up to my rockers, or I look under and the whole bottom of the trans is a frozen slush ball. It also does go in the bush time to time so I'm afraid a stick will tug the wire too.

 

[stutaeng]

@PlayingWithTBI and @Duallylife I honestly don't think it's going to be much of a difference. From basic theory of fluid mechanics, heat will ALWAYS flow from hot to cold. So even if you have a little static pocket of fluid that doesn't flow, heat will get to it and you will see that temperature rise. And the flow really depends on if it's laminar vs turbulent....I'm no mechanical engineer, but understand basic stuff. Even if you get a short burst of heat, the fluid should provide enough thermal mass to maintain the heat under control (along with cooler, etc.). The problem would be when there's nowhere for that heat to go. I don't know if that makes sense or not.

Given the OP's constraints, I would say just install it. If it doesn't work, he can install the other alternates and he's out $20.

In the end, I don't really care if the transmission fluid is 189.98 vs 190.01F. I look at my guages kinda like a "LOW," "OK," and "OH $hit!" graduations. And I agree that any guage is better than no guage.

I will add that plow trucks are one of the most severe uses of these units...change your fluid/filter frequently.

 

[Duallylife]

This truck gets more trans fluid changes then oil... I know who the hell is that dumb... But I haven't changed engine oil in almost 2yrs, almost 30k kms. Just top it up here and there haha. The trans gets new oil/filter with a flush once a year, usually just before plow season.