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BayStYat
Samba Member
Joined: July 30, 2020
Posts: 152
Location: Gulf Coast MS
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 Posted: Sat Jun 07, 2025 9:19 am Post subject: Mechanical Trans Temp Gauge |
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I am going to install a mechanical trans temp gauge. I want to install the sensor in the oil pan. Is the trans oil temperature an indication of how hot the transmission is?
Thank you |
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67rustavenger
Samba Member
Joined: February 24, 2015
Posts: 10967
Location: Oregon
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| Posted: Sat Jun 07, 2025 10:21 am Post subject: Re: Mechanical Trans Temp Gauge |
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| BayStYat wrote: |
I am going to install a mechanical trans temp gauge. I want to install the sensor in the oil pan. Is the trans oil temperature an indication of how hot the transmission is?
Thank you |
Short answer, Yes.
There is an easier way to measure trans fluid temps.
Buy and install a "Scan Gauge." It plugs into the ODB port under the steering wheel and measures just about everything going on with your engine and transmission.
You can also scan CEL codes and clear them if needed.
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!
There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!
2003 Astrovan? GFYS again, Xevin!  |
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dsh1705 
Samba Member
Joined: June 11, 2014
Posts: 128
Location: Seattle, WA
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| Posted: Sat Jun 07, 2025 10:27 am Post subject: Re: Mechanical Trans Temp Gauge |
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| Quote: |
| Buy and install a "Scan Gauge” |
This only works if you have a 97 or later EuroVan with OBD2.
I installed an in-line sensor in my transmission cooler on my 95.
_________________
David
1705.net
95 EVC
ACU,098 |
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67rustavenger
Samba Member
Joined: February 24, 2015
Posts: 10967
Location: Oregon
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| Posted: Sat Jun 07, 2025 10:46 am Post subject: Re: Mechanical Trans Temp Gauge |
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| dsh1705 wrote: |
| Quote: |
| Buy and install a "Scan Gauge” |
This only works if you have a 97 or later EuroVan with OBD2.
I installed an in-line sensor in my transmission cooler on my 95. |
Fair enough. BayStYat didn't state what year van he has.
Looking at his gallery pic, because there's only one. He has an image of a Scan Gauge II readout.
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!
There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!
2003 Astrovan? GFYS again, Xevin! |
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BayStYat
Samba Member
Joined: July 30, 2020
Posts: 152
Location: Gulf Coast MS
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| Posted: Sat Jun 07, 2025 3:27 pm Post subject: Re: Mechanical Trans Temp Gauge |
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| 67rustavenger wrote: |
| dsh1705 wrote: |
| Quote: |
| Buy and install a "Scan Gauge” |
This only works if you have a 97 or later EuroVan with OBD2.
I installed an in-line sensor in my transmission cooler on my 95. |
Fair enough. BayStYat didn't state what year van he has.
Looking at his gallery pic, because there's only one. He has an image of a Scan Gauge II readout. |
Sorry it’s a 2002. I have a scan gauge but it so dam inaccurate. |
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67rustavenger
Samba Member
Joined: February 24, 2015
Posts: 10967
Location: Oregon
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| Posted: Sat Jun 07, 2025 3:55 pm Post subject: Re: Mechanical Trans Temp Gauge |
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| BayStYat wrote: |
| 67rustavenger wrote: |
| dsh1705 wrote: |
| Quote: |
| Buy and install a "Scan Gauge” |
This only works if you have a 97 or later EuroVan with OBD2.
I installed an in-line sensor in my transmission cooler on my 95. |
Fair enough. BayStYat didn't state what year van he has.
Looking at his gallery pic, because there's only one. He has an image of a Scan Gauge II readout. |
Sorry it’s a 2002. I have a scan gauge but it so dam inaccurate. |
Really?
My scan gauge was reading funky last weekend on the way home from a campout.
It was showing the trans temp way lower than the engine temp.
I unplugged it waited 30 seconds and plugged it back in.
Then the readings were matching.
It's strange that your is inaccurate.
_________________
I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!
There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo!
2003 Astrovan? GFYS again, Xevin! |
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BayStYat
Samba Member
Joined: July 30, 2020
Posts: 152
Location: Gulf Coast MS
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| Posted: Sat Jun 07, 2025 4:21 pm Post subject: Re: Mechanical Trans Temp Gauge |
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| BayStYat wrote: |
| 67rustavenger wrote: |
| dsh1705 wrote: |
| Quote: |
| Buy and install a "Scan Gauge” |
This only works if you have a 97 or later EuroVan with OBD2.
I installed an in-line sensor in my transmission cooler on my 95. |
Fair enough. BayStYat didn't state what year van he has.
Looking at his gallery pic, because there's only one. He has an image of a Scan Gauge II readout. |
Sorry it’s a 2002. I have a scan gauge but it so dam inaccurate. |
Well I was changing my trans oil Friday and the gauge would hold 85deg for about 4 minutes then jump to 105 then back to 85. I was checking the pan with a temp gun and it was at 110 and climbing ever so slightly but the scan gauge was just sitting back at 85.
It’s so dam annoying |
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kourt
Samba Member
Joined: August 13, 2013
Posts: 2305
Location: Austin, TX
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| Posted: Sat Jun 07, 2025 10:23 pm Post subject: Re: Mechanical Trans Temp Gauge |
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You need to check if your ScanGauge has the Eurovan firmware. Did you get it from BusDepot? If not, it likely does not have the correct firmware.
The temp jumping you describe is a symptom of incorrect firmware.
Any regular ScanGauge will not come properly configured to read Eurovan trans temps out of the box.
Contact ScanGauge customer service to remedy this. They will have you send in your gauge for an update at a reasonable fee.
kourt |
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BayStYat
Samba Member
Joined: July 30, 2020
Posts: 152
Location: Gulf Coast MS
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| Posted: Sun Jun 08, 2025 4:41 am Post subject: Re: Mechanical Trans Temp Gauge |
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| kourt wrote: |
You need to check if your ScanGauge has the Eurovan firmware. Did you get it from BusDepot? If not, it likely does not have the correct firmware.
The temp jumping you describe is a symptom of incorrect firmware.
Any regular ScanGauge will not come properly configured to read Eurovan trans temps out of the box.
Contact ScanGauge customer service to remedy this. They will have you send in your gauge for an update at a reasonable fee.
kourt |
Kourt
I did send it in and had it updated. |
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dsh1705
Samba Member
Joined: June 11, 2014
Posts: 128
Location: Seattle, WA
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BayStYat
Samba Member
Joined: July 30, 2020
Posts: 152
Location: Gulf Coast MS
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| Posted: Sun Jun 08, 2025 8:52 am Post subject: Re: Mechanical Trans Temp Gauge |
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That’s where I got the idea. |
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Endopotential
Samba Member
Joined: February 13, 2012
Posts: 291
Location: Just outside SF, CA
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| Posted: Sun Jun 15, 2025 3:38 pm Post subject: Re: Mechanical Trans Temp Gauge |
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I added that manual transmission temp gauge. It's a nice feature, but I've found it to be quite inaccurate.
If you can get your Scan Gauge / Torque Pro / any OBD2 reader to work, I would go with that, as presumably that's what data the ECU is actually using to function.
With the manual gauge, it sometimes reads 15-20F below OBD2. And because the temp probe is bolted to the transmission housing, I think there is likely a "heat soak" phenomenon so that it doesn't ramp up and down quickly enough to be super accurate. |
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bigfoot_ev
Samba Member
Joined: March 13, 2018
Posts: 281
Location: P.NW
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| Posted: Sun Jun 15, 2025 9:14 pm Post subject: Re: Mechanical Trans Temp Gauge |
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This conversation is good timing for me since I just did a transmission oil change today and I needed to get the trans temp up to the proper temperature.
I started out using Torque and a bluetooth OBD II dongle. What could be more convenient than to walk around the garage or under the van and monitor trans temp? The strange thing is that the temp seemed to be stuck on 86 F. So, I started to get nervous and decided to switch to VCDS. That meant unplugging my OBD II dongle and plugging in the VCDS cable.
After getting the swap set up the trans temp went to (sorry SWITCHING to deg C) 33 C. Then it sat for a bit, but then jumped to 36 C and falling back to 33 C every now and then. Finally after quite a while it hit 40 C, my target, but again falling back to 36 C every now and then. So, I am seeing the same as BayStYat with VCDS.
What I thought was interesting is that VCDS, the so-called gold standard, only showed 33 C, 36 C, 40 C, and fluctuated between them. My take-away is that Torque works just as well and the resolution is not that precise coming from the TCU.
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2003 Westfalia Weekender, AXK, 01P |
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Endopotential
Samba Member
Joined: February 13, 2012
Posts: 291
Location: Just outside SF, CA
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| Posted: Sun Jun 15, 2025 11:29 pm Post subject: Re: Mechanical Trans Temp Gauge |
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That's an interesting observation Bigfoot. I wonder if others could comment as well.
With my Torque Pro, the readings seem to update every 10 seconds or so. Which hopefully is accurate enough for doing the fluid change and monitoring things on the road.
With the analog dash gauge, the needle doesn't move anywhere rapidly enough. I even tried an infrared thermometer but the heat soak phenomenon and time needed to heat up the metal of the transmission pan seemed to generate wildly inaccurate readings.
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2002 Eurovan Weekender |
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bigfoot_ev
Samba Member
Joined: March 13, 2018
Posts: 281
Location: P.NW
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| Posted: Mon Jun 16, 2025 8:51 am Post subject: Re: Mechanical Trans Temp Gauge |
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I just realized we might be talking about 2 different scenarios. The first is waiting for a cold engine/trans to warm up and monitoring the temp from cold. The second is driving along for some time after the engine and trans have had time to come to operating temp and monitoring ongoing temps.
Specifically, in the first scenario I get very little temperature resolution. And while just idling it takes a long time to hit target temp.
However, in the second scenario as I'm traveling along glancing at the trans temp, especially going up hills it seems I get frequent and higher resolution temperature readings. This is just seat of the pants no real close monitoring. That would need a second person tracking data.
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2003 Westfalia Weekender, AXK, 01P |
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Endopotential
Samba Member
Joined: February 13, 2012
Posts: 291
Location: Just outside SF, CA
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| Posted: Mon Jun 16, 2025 10:21 am Post subject: Re: Mechanical Trans Temp Gauge |
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Yes, excellent point. That's exactly my experience.
The warm up period from a cold start does take a while, especially during the transmission fluid change when your hands are all greasy and you just want to finish the job.
It was only when I got Torque Pro configured to find transmission temp (thanks to you Bigfoot or HeyCrutch I believe, thank you!) that I was able to do the fluid change with more confidence.
With the van warmed up and running on the highway, OBD2 readings are quite granular.
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2002 Eurovan Weekender |
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