Safe transmission temps

[krusovice]

My wife and I just did our test camping run in our “new to us” EVC. Slept great and had a wonderful weekend. There are some things to tweak but overall very happy.

I have a Scangauge II installed (that was sent back to them for the correct firmware) and I watched the trans temps carefully. Ambient temp was in the 60s and we don’t have a lot of hills here. At steady 55-60 mph I was seeing 204-212 for trans temps. The last 2 miles are gravel at 20mph and temps peaked at 217.

From what I’m reading, 190-200 is optimal, and over 225 is where fluid starts to breakdown.

So can anyone make me feel more at ease? Am I in a safe operating range?

(And, yes, I hope to install a trans cooler when I can find the time and confidence.)

Thanks
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1984 Vanagon 1.9/4 speed
2001 Eurovan Camper

[kourt]

The amount of time spent above 225 is what matters.

Hours? Yes, the fluid will be affected by that.

Twenty minutes to get to your destination? Probably not an issue.

I had a few instances of 240 degree ATF on a recent trip to the Gila Wilderness.

Later, I took down the trans pan and changed the fluid. It was two years old and had 20,000 miles on it. The fluid color and smell were pretty normal for that lifespan.

I would recommend an external cooler.

kourt

[Abscate]

[krusovice]

Hopefully it gets warmer soon! But the Midwest is not too hilly.

I was ready to pull the trigger on a trans cooler, but now I’m leaning towards changing the fluid and monitoring it. I don’t know how long it’s been in there so if I end up doing a second change to install a cooler later that won’t be the worst thing.

(The answers from the fluid guy were interesting and made me feel better. It sounds like as long as I can keep it below 250 ithe fluid stays stable, and I hope to be able to keep it below 225 in our environs - plus I’m not in a hurry. I’ll do some more research.)
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1984 Vanagon 1.9/4 speed
2001 Eurovan Camper

[kourt]

Abscate has done good work in countering the fearmongering that surrounds Eurovan automatic transmissions. I am in alignment with his belief that a properly serviced Eurovan automatic will deliver reliable results.

In my world, where summers are 110F and I am regularly driving in the mountain west, I choose the alternative path of an aftermarket cooler. However, I would easily accept and defend Abscate's position if I had a slightly different use case.

I'm still changing my ATF every 20k miles, monitoring temps, using good driving practices, and employing an external cooler. Belt and suspenders.

kourt

[HeyCrutch]

Posting this simply as a data point:

One Year Ago: I purchased the 2002 EVC last July (2024) with 77,400 original miles on the van and no modifications of note. The van had been serviced exclusively at VW dealers for its lifetime (including an ignition switch replacement days before I bought it). The only issues the van had experienced per the service records related to the Spiral/Clock spring, which was replaced 3 times in the first few years of the van's existence, and then cracked radiator fan blades, which necessitated replacement. Otherwise the van has performed admirably. The second owner - from whom I purchase the van, had the A/T fluid drained & refilled every 2-3 years, and he had oil changes done every single year, even thought the van was hardly being driven for many of those. The van only has it's original trans cooler, which I assume works as designed (but I don't really know for sure).

When I drove the van home from California to North Carolina last July, I connected my ScanGauge II to the OBDII port to monitor things (as I had been accustomed to doing in my 1997 EVC with an external cooler). On the drive home daytime temps peaked around 100-105 everyday so I drove mainly in the very early hours of each day and stopped by noon to avoid the worst of the heat. The Trans temp readings on the ScanGauge on this drive home were between 225 and 240 most of the time I would be driving (and as high as 250 if I ended up in stop and go traffic after hours on the highway). Water temp would be between 190 and 210 (and as high as 215 in stop go). It absolutely concerned me because I was used to 185-205 as typical temp in the 97 van with the ext cooler. But I didn't have much choice being on the road but to avoid the daily heat and get the van home.. I assumed the high TFT reading was because of the extremely high ambient air temperatures which is why I would stop driving by 11am or noon each day. Climate Change is a bear.

Anyway, the van got home alright, despite the heat, and I've been working on it for the past year restoring much of the interior and making lots of modifications. I have purchased an external cooler from GoWesty but haven't had it installed yet. But it's only accumulated a couple hundred miles from short drives around town.

TODAY ... I drove my partner 75 minutes away to an airport and drove the van (the 2002 EVC under discussion) at speeds around 65mp to 70mph. Should note that the External cooler still hasn't been installed. Ambient outside air temps were between 55 and 65 degrees. I was driving down the Blue Ridge Escarpment, so wasn't climbing. TFT reading on the ScanGauge settled in around 230 F. It would get as high as 250 upon exiting the freeway and moving into stop and go traffic. Basically the same temps that I saw last July on cross-country drive in extreme heat.

Which means my assumption that the high temps for the A/T fluid was because of the extreme ambient air temps appears was flawed (or at least incorrect).

I have two ScanGauge II monitors so I tried them both and got the same results - so it's not an issues with the gauge.

Which brings me back to square one ... either there's
a) something wrong with the original stock VW trans cooler that is preventing it from cooling the fluid (which would be bad);
b) something off about the data stream, ... OR
c) VW was OKAY with trans fluid temps in the range I experienced and considered that to be the normal operating temperature.

Given that everything one reads about trans fluid not he internet suggests that you shouldn't be running at 235-240 regularly, I'm inclined to say that VW would not have been okay with those temps regularly.

But I also have to admit that I have no idea what VW expected the van's A/T fluid to run at under normal conditions (which I was experiencing today). That's kind of the whole point of this discussion.

Now, I will be getting the external cooler installed, it's just been one of those things that I've been putting off (remember the van hasn't been driven much lately). But it still begs the very valid question of WHAT exactly are the temps that VW expected the van too run at.

I wish I had used the scan gauge on my 97 EVC before I installed its cooler, but I didn't have it yet. That data would have been nice to compare.

I should note that the van shifts VERY smoothly and hasn't given me ANY transmission issues since I've had it (not on the drive home, not around town, ... not today).

I'm also not suggesting that 235-240 temps are okay. I don't think that, based on what I read about trans fluid.

Yet, I wonder why this van's temps read that, in the stock configuration. Probably gonna have one of the local shops provide some input, but thought I would add this as a data point about what "normal operating transmission fluid temps" are for the van.
_________________
-2003 EV MV Wk - Forest - 51k
-2002 EV Camper - Ghost - 82k
-2003 EV GLS - Fluffhead - 176k

-1997 EVC - 12vVR6 (SOLD 5/2025)

[Endopotential]

@HeyCrutch - thanks for that detailed and very coherent writeup.

I learned a lot from my tinkering last Thanksgiving with my own cooling system
The peanut gallery chimed in with some great info and photos.

First off "trust but verify." Have you checked the transmission fluid level yourself, just to make sure the shop guys actually knew what they were doing? And did you replace those green resistor coils under the bumper and check that the fans are turning on adequately? I'm glad and surprised that your transmission didn't have any problems at those temps - mine would start slipping gears above 230F.

I also learned that just having any old external cooler isn't necessarily sufficient. The one originally installed in mine was woefully undersized and made it worse than just keeping the OEM setup. Now with my 2.5x larger cooler it's much better. I'm sure the GoWesty system is fine.

It never drops to freezing here in the SF Bay Area so I'm not gonna bother with a thermal bypass valve. But on the other end of the equation, I've never found out what TOO LOW of a transmission temp would be.

[HeyCrutch]

[gesoffen]

For my '03 Weekender using the stock ATF cooler, I would regularly see ATF temps of 220-230F on freeways and 240-260 in stop/go. I saw 270+ a few times when doing light offroading climbs (think fire roads or similar). Somewhere in the low 270s, it will trigger a CEL for torque converter lockup due to the excess ATF temps.

After external cooler install (and removing the stock cooler), freeway temps would be in the 180-200 range and stop/go temps were in the 220-230 range. I haven't done the fire road since the external cooler install so I don't have a direct comparison to that one. I installed the gowesty kit with the thermostat designed to open at 180F.

With synthetic fluids and regular services, ATF temps in the 240-260 range aren't concerning. Though, at those temps you will need to shorten the service intervals. If memory serves correct, VW recommended ATF service at 40k or 50k miles. I would argue that those intervals are way too long for the capabilities of the stock system.

[krusovice]

Thanks, all, for the data points.

I'm feeling better about 205-215 now. I will replace the fluid and track the data for a bit. If I'm still concerned, at least I'll know I cleaned out the trans before installing a cooler.

I don't want to run it too cool, either. And if I don't have to add another failure point (no matter how well designed), I'd rather not.
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1984 Vanagon 1.9/4 speed
2001 Eurovan Camper

[kourt]

My 2001 EVC with GW external ATF cooler gets 180 to 195 at 80 MPH on the interstates in the summer (90 to 100 degrees F outside).

Around town, in stop/go, I have to watch it. It can run up to 220 easily with so little forward motion.

I get around this problem by just running the air conditioner, which runs the condenser fans and therefore draws air over the ATF cooler. That moderates things down in the 210 range.

kourt

[mikemtnbike]

since this thread talks about servicing the AT giving my service "tip"- let the AT drain overnight. I do this with the pan off (well, no other way to drain it on a 1995, but anyway) and a rubbermaid tub that wraps around the bottom of the transmission to reduce the odds of any wind-blown or other foreign materials getting in to the internals.

I got somewhere between 1-2 quarts more drained out doing this- the slow drips really accumulate and the more old fluid you get out, the better.
_________________
1991 Vanagon GL 2.1 AT Westfauxlia. "Frankie" Totaled https://www.thesamba.com/vw/forum/viewtopic.php?t=764510&highlight=carnage
1995 Eurovan Camper "Marzivan"
2020 GTI SE manual

[Endopotential]

[kourt]

Yes, it is the fans behind the radiator. Not running at high speed, just normal speed. Those fans are not full time fans. They run conditionally. One condition is by a certain engine or water temp, which you can't control. The other condition is if the air conditioner is running, which you can control. So turn on the air conditioner to get manual control of the fans. Old Vanagon trick.

When driving slow around town, the engine is just not taxed, and those fans are not on 100% of the time. They only come on by thermostatic switches. Using the air conditioner overrides those switches, as the air conditioner will not cool without air blowing over the condenser.

kourt

[krusovice]

Short follow up from the mid-point of our initial camping trip in the UP of Michigan. Not a ton of hills here, but some of the climbs out of Houghton/Hancock are taxing.

The trans temps are higher than I'd like. At 65 I'm running around 215-220. In town after the freeway, as high as 230 (231 once!). Drive's great (knock wood) but I'd be happier with lower temps. I'm all but decided to install a cooler just for the peace of mind.

(On another note, I need to buy Kourt a beer (or a case...). Pulling into our campsite the Scangauge FTW read 210. Most I've seen. But the regular gauge was normal (idiot gauge), the fans weren't running, coolant and oil seemed fine. Quick search: VWs need to use WTR to get the coolant temp (and my scan gauge is correctly programmed). DOH! That one reads much better.

More to follow upon my return. Thanks again for a great resource!
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1984 Vanagon 1.9/4 speed
2001 Eurovan Camper

[VanGeek]

With the stock cooler on my 2001 with 85k miles, the scanguage consistently showed high temps at highway speeds in the summer. Routinely around 230. Temps would go higher if running on the highway, exiting, and driving stop and go on side streets. I saw crazy high temps (250+)when climbing long hills at lower speeds on back roads

This seemed too high so I installed an external cooler. Takes longer to warm up fluid but still gets to 170-180 in 10 to 15 mins. In extreme heat and slow hill climbs to a trailhead, temps will creep over 200 but that's rare. So, for me the external cooler was a good choice.

I don't drive the van in winter, but in the Fall with temps near freezing at night, it takes longer to warm the fluid -- even with the bypass installed -- and generally seems to run closer to 160-170 which is a bit cool.

Some others here seem to report lower temps than I did with the stock cooler. Not sure why, but I recall seeing somewhere that VW improved the stock cooler in 2002 to increase the number of heat exchange passes and perform slightly better.

[kourt]

[krusovice]

[SambaBurnsRed]

PO installed this type of cooler, most likely from GTA when the trans was rebuilt.

CHERISH-AUTO 1PCS OEM LPD49211

The cooler failed/leaked at the entry pipe joint.
Slowly bled ATF over the next 140K miles.
Service history shows trans fluid service/refill every 2 years
Until the tranny lost the first gear clutch pack, etc. due to chronic low fluid.
And created a mess of dirt and ATF on the belly pan, that took some digging off, and cleaning to resolve.

None of the shops caught the leak. I went with a smaller $40 pipe-style cooler now, more robust design. Cruising around 200 ish but our ambients are lower on the coast in BC here.

[WorthaTry]