Syncro trans temps. How hot is too hot?

[Syncro Jael]

I have been watching my tranny temps very closely this summer.

Syncro - EJ22 - Stock gearing - 215/75/15 tires - Weddle pump and cooler.

Mine is set up so the pump and cooling fan can be turned on manually. I normally turn on the pump at 120°f to utilize the filtering system. Then I turn on the cooling fan at 140°f or when approaching a grade that I know I will be dropping down into 3rd gear. You can visually watch the temp gauges climb on each gauge (water, engine oil, trans temp) when pushing the brick up long grades.

I used to also have a skid plate with a scoop. I have now removed it and now just have bar stock down each side of the transaxle for protection.

On my last road trip we drove straight from northern Montana to central Utah. Around 650 miles. It was done in 95° ambient temps at 60-75mph. I ran my gear oil cooler all the time and the highest temps recorded were 167°f and that was pulling a long steep grade in 3rd gear. Most of the time it will run in the 140° to low 150° range at highway speeds with the cooling fan on. My van weighed in at 6400lbs with all of our gear on this trip.

My stop to cool temp is 170°. I also have a full aluminum rebuilt transaxle from AA Transaxle.

_________________
1987 Syncro Westfalia Hightop - NAHT
Subaru EJ25 Forged Frankenmotor, Triple Knob.
Jael = (Mountain Goat)

[Sodo]

[Jon_slider]

Total tranny temps IF ambient were 95F (with NO tranny coolers)

Hans 4:86 R&P: 175F 27.8" tires, diesel
Carterzest 4:86 R&P: 182F 25.3" tires, waterboxer
Jahbah 4:86 R&P: 191F 27.8" tires, subaru 2.5
Frankensubysyncro 6:17 R&P: 204F 29.5" tires, subaru 2.5 (I believe this van has the most extensive skid plating of the group, and the tallest lift)
Christopher Schimke 5:43 R&P: 207F 29.1" tires, waterboxer

Note the two vans with larger than 28" tires ran hotter than the ones with 28" or less. The larger tires are mated to shorter ring and pinions, both factors add heat.

[Waldi]

Yes, reducing the rpms by taler tires or taler r+p or 4th gear on a gazer engine is contraproductiv.
The overall ratio (gearbox and tires) from a stock wbx is here the best.
You have some revs more, but you need to press the pedal less.

Looking at the dates i see the gearboxes of gazer engines run hotter than diesel. The reason cannot be inside the gearbox.

I see a full skid plate as the first reason for high temps.
Just think about the hot air coming from the watercooler.

[Reventlos]

Great info, thanks to all! We are heading home tomorrow, and I will try to find a Sears on the way and get a heat gun. All the data and hunches posted makes sense, and I may need to rethink my set-up. I'm also aware of how tempting it is to flog it in 2nd & 3rd! Matt Q

[Jon_slider]

I hope you share a couple photos of your trip

I also hope all the fear of high temperatures proves harmless.

A photo of your drain plug magnet would be very informing.

here are a couple of threads with pics of other peoples drain plug magnets:
http://www.thesamba.com/vw/forum/viewtopic.php?t=418356

http://www.thesamba.com/vw/forum/viewtopic.php?t=596332&postdays=0&postorder=asc&start=0

Syncro Jael has a system with additional magnets at the filter, not sure where that link is atm
_________________
My Soapboxes: Inflation; Handling; Gearing; Decoupling; Swepco

[Reventlos]

As the OP, I thought I would bump this thread, due to all the great recent Syncro trans discussions. It seems like a lot of owners are at least thinking about trans coolers, regardless if they are running bigger motors or not.

I have tweaked my set-up, and thought I would post some results. To recap: My Syncro tiptop with full Burley skid plate was experiencing extreme (indicated) oil temps after my SAH 1.8T transplant. I installed a kit from Weddle, but still was seeing way too high temps. On advice of the forum, I bought a cheap IR heat gun from Sears, and took some actual readings off the case. Surprise! Assuming the gun is correct, my gauge is off by a considerable margin. With ambient temps about 95 and indicated trans temps well over 200, I could find nothing on the case reading over 189. Still way too hot, but not quite as heart-stopping. The next step was to take off my skid plate and take additional readings. No surprise here, but it made at least a 10-15 degree difference with the skid plate removed.

So, what to do now? I took my skid plate (thick enough to up armor a humvee) to my friendly local metal shop, and had it made into swiss cheese. I relocated my cooling fan slightly for better air circulation, and put the system on a master switch so I can control it. Voila! On my last extended trip in heat, over grades and under load, I seem to be at least close to happy land, seeing no temps over about 165. I also purchased a bigger cooler/fan unit from Salim at Country Homes, which I will install next summer if i feel that the kinda wimpy Weddle unit is not up the task. I should add that my set-up is nothing compared to the incredibly engineered Jael unit. I suppose the next step is to go the neo magnet route on the filter.

Random observations: I'm still amazed how quickly the trans heats up when going up a freeway grade. Now that the system is working properly, I'm also amazed at how quickly the temps come down when I engage the pump/cooler. Pretty dramatic. Happy trails, Matt Q

[Pcforno]

Nice troubleshooting Matt!

[Sodo]

Hey Matt, since you are hot on the trail of heat

All of the heat that exits the radiator up front comes out under the van into the area where your oilcooler resides. (as Waldi wrote many times - but he refers to the radiator as "watercooler") Theres also hot air above hot pavement. And radiance too from hot pavement.

When you're under the van with the IR gun "you might" (for the annals of Vanagon Science )
---- squirt some of the frame members (quickly) as they may indicate "undervan ambient temp". Then quickly squirt the sheetmetal of the car up higher, outside, someplace NOT heated by roadway or radiator heat. The goal being to see if theres a temp difference between undervan and "not undervan". The emissivity of the test surface can read different - if you can paint some specific 'targets' flat black the data may be more consistent.

I was thinking your temps 230-260F were excessive, glad it was a guage error. Where is your (guage) temp sensor located?

But 190F is still high, the pump system should get you down to the 160s. You might measure your pump flow (at the return to the trans) and verify you're getting 2 gallons per minute flow.

Happy to see others testing & reporting! I'd do all this but its already rainy up here in the PNW, you are more likely to have nice test days in CA.
_________________


'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

[phatveedub]

Matt, I run a 3.0 Subaru with an external transaxle cooler set up. 225/75R16 tires (29.3"). Weddle pump/filter. Initially I had the Setrab cooler with fan, which did ok. I have recently upgraded to a larger Derale unit with twin fans. I have the cooler mounted on the front cross member. Used to have a skid plate up front too, but found that it basically channeled the hot air from the radiator directly into the trans cooler. I have since removed the skid plate and that has helped to drop the temps quite a bit. I live in Sacramento and it's HOT here in the summer. On the hottest days (over 100F out), and going up the hill to Tahoe (75 mph or so), trans temp barely hit 150F. Regular highway driving (65-70) on a hot day (90F+) is in the 130's at the trans. I tend to run the pump and fan all the time when the system is up to operating temp. This ensures good trans oil flow to all the critical places under all circumstances. The biggest gain I have experienced is by using a larger plate style cooler with hi flow fans located in a place that gets good air flow through the cooler. Also, use large gauge wire for the pump and fan(s) with relays. It makes a difference. I noticed that your cooler is mounted horizontally to the bottom of the van. Not the best place to get good heat transfer out of the cooler. Try to find a vertical location if possible to channel air through it while you're driving and with the fan. Last weekend with cooler temps outside (65-70F), drove up to Descend on Bend and back home. 900 miles of 65-75+ mph driving and the max trans temp was 122F. Usually it was 110-115F. Here's a pic of the set up:

I've had the cooler installed for a few years but have really got it dialed in over the past year. Just hope it extends the life of the trans!

Dave

[jberger]

I am beginning to think that cooling of transaxle oil may not really be the issue. From what I have read in auto\racing\industrial sources, mid to high 200º's is normal and in fact, if you cool your oil too much, it is not protecting as intended. 20-40º differentials are not to blame for component failure. Now providing lubrication where it is needed (ports, nozzles, pressure lubing) certainly can't hurt.

[gears]

Overheated oil never has been the issue. A grossly overheated 4th gear is the real problem.

So, the best way to cool 4th gear (and adjacent overheated MS ball bearing) is with cooled oil
.. and as long as we're delivering cooled and cleaned oil, two other potential problem areas are addressed: Pinion bearing and mainshaft needle bearing.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[Sodo]

Also, one must conclude that.... under "similar conditions", the trans temps should be "similar". Temps higher than others suggests higher friction which suggests a "problem".

Agreed that supplying oil is the first concern. But since we're putting double the HP thru the trans, adding a radiator to cool the hot spots is a no-brainer.
_________________


'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

[gears]

And of course the only time you really use 150hp (for longer than a few seconds) is when in 4th gear. Holding an overloaded Vanagon at speed up an incline being a prime example of when 4th gear is really being overheated.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[Waldi]

Sodo and others,
"WE" are over 90% vanagon drivers that dont have "double" 225hp? and WE are happy with a stock gearbox whitch needs to be overhault 2-3 tinmes in a life with good parts and some small modifications.
WE dont have oil temp problems or 4-th gear problems.

The main construction problems on "our" gearboxes are well known and cannot dissapear with oil filtering and cooling.

1. Synchronizer 3-4 (4-5) = solved
2. Synchronizer G-R (1-R) = cain be solved by using a new one every 200k km better earlier on 5-G 2-wd boxes.
3. shifting shaft bearings = use new ones if possible every time your box is open.
4. moving main ball bearing = use a retainer
5. use SA oil plates. THAT is a no brainer.


Its going on my balls, if 5% of van users with a "big engine complex" are thinking/speaking about a overall problem.

I opened today 2 Syncro boxes with about 200k km.
Both had the new style 3-4 syncronizer, and both had not one overused/broken part. Even the main bearings had no clearance.

[Waldi]

Paul,
i cant belive, the 4-th gear is producing significant heat.
There is no data that prove this.
I think that even driving with 150hp uphill in 4th will show the hottest spot on the main bearing(r+p bearing).
This heat does not come from the teeth of the r+p, but from the bearing itselfe.
Same on the 4th gear. Heavy load forces the both shafts going apart,that means the load is going to the ball bearing and the roler bearing.

I will have no problem to say "i am wrong", if somebody show some true data from overheating 4-th gear wheels on a normal working gearbox.

Edit:
Another question is, who has 150hp 4th gear ? A over the top chiped AFN ?

[gears]

Sure. Any time fusing is occurring, the gear is overheating. In more extreme cases, the needles fuse to the gear bore. In the most extreme cases, the mainshaft bearing surface is ruined.

This is NOT a VW-only problem. Other vehicles also suffer from overheated top gears during extended highway use.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[Waldi]

Paul, i know you know this.
On load the shift wheel doesnt turn.
If there is worn out on the needle bearing, there is another problem.
For example, the needle cage get bloked by a sharp grade of the save ring (synchronizer)
I did never seen a heat problem on a TDI fired gearbox, but i have seen broken teeth which has nothing to do with heat.

I have seen also broken teeth on many other gearboxes.

[gears]

Yes, of course it doesn't turn in relation to the shaft. It sits there building up heat. Heat in the idler (MS) gear has only 2 paths to directly pass the heat along .. mainshaft bearing race (primary) and stationary needles (secondary). At these heat transfer points, fusing occurs during gross overheating of the gear.
_________________
aka Pablo, Geary
9.36 @ 146 in '86 Hot & Sticky
'90 Syncro Westy SVX
'87 Syncro GL 2.5
https://guardtransaxle.com

[Waldi]

The rurning gears cannot produce enoph heat to damage the metal.
If that would be the case, there would be first blue teeth on the wheel.
This can only happen with a non moving needle bearing, while in other gears.

The most load is usually on the 3rd gear. There you can use realy the full power for long time.

With the comon gazer engines in USA there is no way to have full power in 4th gear. 1,8t has 150hp on 6000revs.

I have seen in over 100 gearboxes only 2 melted needle cages on 4th. And this was in boxes with low oil and stock engines.