Manual Transaxle temperature gauge for $20 (how-to with pics)

[Sodo]

Very low cost transaxle temperature gauge for the Vanagon 4 speed manual transaxle.
I installed one temporarily for another project but realized I could make a "how-to" fairly easily.
It's fairly simple project for those wondering if their driving style (big engine, 75mph) is killing their transaxle.

It's a temperature controller that you can use just for the display.
But it can turn on a warning light or buzzer if you are so inclined.
Later, you can drill into the gearbox and put a 'real' sensor in the oil if it comes to that.

Maybe someone can figure out the right location to monitor an Auto trans but tha should be a different thread.

Here is the temp controller sitting in a cup holder, compared to my main gauge on a cold morning.
When stone cold, outside trans temp is equal to the oil temperature.
Be advised there are "conditions"....
Internal, immersed in oil is the best.
But we're trying to make it easy so you can get a gauge on before summer.

At speed, there will be airflow cooling the outside of the trans and an external gauge will read lower than a sensor in the oil.
But this INKBIRD can be faked to approximate the internal temperature "by comparison".
I will run my trans to 160°F and tell you the "adjustment" so the external gauge will
display a number assumed to be correct at this 'critical temperature'.

And I suppose you want to see the cold morning.
Salt Creek county park campground, on the Olympic Peninsula (WA)

If you have a big engine and like to drive fast in the summertime where it'a 100°F outside,
it's wise to know if your transaxle is getting too hot.

The vanagon transaxle is believed to start damaging itself at appx 180°F.
I'd advise using 160F as a max temperature,
If it approaches 160F, slow down!

A primary area of concern is the mainshaft bearing bore.
It is a thermal-fit bearing that when new, is "loose in it's bore" at 195°F.
From this info, some transaxle builders have said that it loses it's grip on the bearing
at a lesser temperature, and some have settled on 180°F as a max allowable transaxle temp.

Order this temperature controller for the sensor and the digital display.
Inkbird Dual Stage DV 12V Digital Temperature Controller ($14.99)

I have a temperature gauge on my trans, drilled/tapped into the case, with a sensor in the gear oil.
Making the assumption that my temperature reads 'correct' I compared this $14.99 solution with the sensor
applied to the external surface of the transaxle and found that with simple contact under foam insulation,
The difference in temperature with simple 'contact' was 12°F at temps around 140°F on a 50°F day.
So if the in-oil temperature read 140°F the surface-mounted sensor detected 128°F

There are heat-conducting compounds that you can buy, but being the cheap bastard that I am,
and just doing this as a Public Service Announcement for you thankless Samba fellers,
I was only willing to spend $3 at HomeDepot.
So I used Noalox, which is an electrical conduction enhancer, as a thermal conductive paste.
If I was willing to drop $4 I would have chosen Ox-Gard which LISTS thermal conductivity on their website. Lowes sells Ox-Gard.
They both have powdered aluminum and zinc in a paste.
Using Noalox paste reduced the discrepancy from 12°F to 6°F at appx 140F.

There are other heat-transfer compounds you can buy for computer heat-sinks, for those who hot-rod gaming computers. Some cost $20 for the size of a pea and others, not much more than the $3 solution.
But I neede one from a hardware store enroute to the campground.

It's very easy in the settings, to 'bump up' the temperature reading by 6 points to make it "correct at 140°F."
Someday soon (I hope) I'll get you the delta to be "correct at 160°F" but that has to wait until I climb a mountain pass.
The goal is to approximate internal oil temperature at highway speeds, correcting for 'outside cooling airflow'. I don't know how to get this 'correction' otherwise.

Here's what i did to install it:

I ran a 2-conductor wire fom the dash area back to the transaxle.
At the dash, it's connected to the sensor inputs on the INKBIRD.
At the trans, it's connected to the two wires of the sensor. Very simple.

Here's the parts for the sensor mounting
A peice of packing foam, and a bent peice of aluminum to hold the foam on.

I set the sensor in a cavity on the trans

Then goobered it with Noalox paste

then packed foam into the cavity

Than jammed the bent aluminum peice onto an adjacent rib to hold the foam in.

The sensor is liberably goobered with Noalox and placed in the cavity then the foam peice is packed into the cavity.
The bent peice of aluminum holds the foam tight in the cavity.
This precision aluminum unit just grips the rib and holds the foam in.


There are many other ways this can be done.
You could shape a little cover that is epoxied over the insulation.
Clamp it on until the epoxy hardens.

Possibly you could simply pot the sensor into the hole with epoxy.
But the "6 degrees" calibration number that matches my gauge is with Noalox and insulation.

OK it's late and I have to go to bed.

I will make another post later abot how to do the INKBIRD setup.
But you can figure it out!
_________________


'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[djkeev]

Excellent!
Thanks for the write up.

Dave
_________________
Stop Dead Photo Links how to post photos

Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473

Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537

Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert

[[email protected]]

Super sweet. Great idea, thanks

[dhaavers]

Simple, affordable, effective...approved!

- Dave
_________________
86 White Wolfsburg Westy Weekender
"The WonderVan"
<EDITED TO PROTECT INNOCENT PIXELS>

[DuncanS]

Just ordered. Thanks

[djkeev]

I put it in my cart.......

I already have a proper digital ATF gauge in hand.

I was thinking of it being an outside ambient thermometer, but it is way too sophisticated for that use. Although the ability to sound a freezing point alarm does have an appeal.

Question, being it is a hardwired +12v, can you (well of course you can) wire it to the ignition circuit and will it remember its settings when the power is cut?
Or does this become a constant key off draw?

Dave
_________________
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Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473

Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537

Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert

[DanHoug]

great write-up! with your temperature monitoring, i would LOVE to see a comparision of gear oils on trans temp.

i've been told by a noted rebuilder of BMW airhead transmissions that he insists on a moly-fortified oil, Schaeffer 293, as he found it lowered trans temps and the internals always looked better on teardown.
_________________
-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[dobryan]

That is a neat way to monitor trans temps for those that do not have a tapped case for the temp sensor. This should get the temp measurement in the right ballpark to know what is happening.
_________________
Dave O
'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD

"To travel hopefully is a better thing than to arrive." Robert Louis Stevenson

MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646

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https://www.thesamba.com/vw/forum/viewtopic.php?t=695371

The Western Syncro build
https://www.thesamba.com/vw/forum/viewtopic.php?t=746794

[tjet]

So is there anything else I would need to order for this, or does it come with everything?

Great idea. I've often wondered if my trans runs warmer because I overfill it.

[MarkWard]

So, are you supposed to pull in the pits when the temps are higher than you desire? Data points are nice when doing studies and making changes, but it would be impossible for me to enjoy driving places with all that auxiliary input. But thanks for sharing.
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☮️

[Jake de Villiers]

That's brilliant, Tom!! All your transaxle obsessing has yielded a terrific result.
Its cheap and easy enough to do that the transaxle temp database will really expand.

Thanks!
_________________
'84 Vanagon GL 1.9 WBX
'86 Westy Weekender Poptop/2.5 Subaru/5 Speed Posi/Audi Front Brakes/16 x 7 Mercedes Wheels - answers to 'Dixie'
@jakedevilliersmusic1
http://sites.google.com/site/subyjake/mydixiedarlin%27
www.crescentbeachguitar.com
www.thebassspa.com

[bobbyblack]

Mark, ya... well said. BUT.. same setup that can trigger a buzzer or light could also trigger a pump and blower for an external trans cooler. Then you'd find your Zen.
_________________
'87 Westy 'Flossie','86 Westy 'R1','86 tintop GL - Subi2.2 'J2','83.5 stock tintop L 'ZoomBus','74 Karmann Ghia, '63 Notch

[Sodo]

[Franklinstower]

per your other question about Subie trans long term reliability, It would be good to know what those tranny's are running for temps too.
_________________
'89 Westy - EJ25/22 Frank 4.44 5mt
'75 Miami Blue Sunroof FI Standard Bug

[DuncanS]

Hard to get to to find a place to epoxy on a temp prob? Not for me.

[space]

very nice
T
_________________
82 westy
w:
2.5 JDM Subie
Rear discs

[Sodo]

Franklinstower Subaru 5MT trans tempurature (pushing the brick!) would be an interesting data point!
The R&P is smaller than VW thus I'd guess tooth pressure is higher/ hotter.
Do you know the % of sliding in the 5MT R&P.
What's the R&P tooth counts?

DuncanS a guy could ride back there and squirt different areas with an IR temp gun !!👍🏽👍🏽

In the past we were curious about the temp at the top front of the trans case where 4th gear idler is.
I think 4th gear gets hot when the trans is ready to give up the ghost.
But it's good to know it 4th gear is hot.
I bet a hot 4th comes with a hairy drain magnet too.

Sensor below the oil level probably shows a good 'average' of the whole transaxle.
In a normal trans, the rear should have more heat because the 190°F engine is nearby, and the hypoid teeth have sliding contact.

4.86 R&P has 25% sliding contact. Most USA vans have 4.86 R&P.
5.43 & 6.17 run hotter.... 6.17 has 40% sliding contact
_________________


'90 Westy EJ25, 2Peloquins, 3knobs, pressure-oiled GT mainshaft, filtered, cooled gearbox
'87 Tintop w 47k 53k, '12 SmallCar EJ25, cooled filtered gearbox
....KTMs, GasGas, SPOT mtb

[Jake de Villiers]

[Steve M.]

I used computer CPU Thermal Lake epoxy on mine 4yrs. ago and still holding strong on the side of the case as close to Fourth Gear as I could get it.

It triggers the cooling Fan and Pump as suggested by SODO way back when he first started do the gearbox cooling mods.
_________________
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[Sodo]