Track and Post your Tranny Temps with IR Thermometer or a Gauge

[Sgt.Gator]

Hi Folks,
I'm doing a survey of what tranny temps our cars are running on the track. Please, the next time you are on a track, when you come in from a session check your transmission in a few places with an IR Thermometer and report what you find here. Or use a temp sensor - trans gauge to report your readings. I've been having trans temp issues and I'm wondering if it's just me? I didn't notice it until I added a trans temp sensor/ gauge. I've confirmed it's reading with an IR thermometer.
I know Dragonfly welded their trans at the PIR Enduro two years ago about 4 hours into the race. I'm wondering if some of the 5 speed failures we are seeing are not because of the weak Subaru 5 speed design, but rather overheating.
This doesn't apply to street driven 818s, although it may be a good idea. But I can drive my 818 for an hour on country roads and have no problem with trans temp. This only appears on a race track where I hit 255 degrees in 15 minutes.

I am running a Cusco plate type LSD and Redline 75W90NS gear oil. I suspect the issue may be the Cusco LSD, so the next step will be swapping in a Quaife LSD.

The IR thermometer is useful for checking all around the engine too!

[Rob T]

Gator: Last track session, at the end of session 2, I saw about 255F on the top of the transmission, passenger side and 195 on the top of the transmission, driver's side. I don't have a fluid temperature yet. 6MT with the internal oil pump. No cooler yet. The blow-off from the turbo is running against the transmission on the passenger side where I measured the 255. It is wrapped, however. I didn't measure right at the exhaust, but in an inch or so. IR sensor with a laser pointer, so I know where I am aiming.

[Sgt.Gator]

From How to Rebuild and Modify Your Manual Transmission
"-once temperatures reach 250 degrees or higher there is no oil that will be able to prevent gear wear and eventual damage."

[Hobby Racer]

As stated in a previous thread 5MT transmissions NEED an oil cooler when driven hard! I saw 280 degrees Fahrenheit after a 20 minute session and that was oil temp via installed sensor.

[fateo66]

Hey guys, I've been away for too long. Looks like my last login was 6 years ago....

I wanted to talk a little bit about what we have seen over the years with the 818 transmissions.

Nearly every 5 speed that we work on that has previously been ran has had evednce of 5th gear overheating. (six speeds are not prone to the same issues beacause all of the important parts are located in the main body and recive a little more splash lubriaction from drving around.) where as the 5th gear on the 5 speeds is located in the mid section which is normally completly dry in the 818 if the transmission is not overfilled.


Here is some of the measurements and angles that I have measured that could assist us in diagnosing why Gator's transmission is getting so hot.

Factory transmissions have roughly a 5.3-5.9* tail down slope from subaru (5mt, 6mt, auto)
My 818 measures out to have a 3* tail up slope and Gator measured out his to have a 3.8* tail up slope base off the top rib of the mid section ( I've measured a few here in the shop and came up with a 2* tail down slope off that rib relative to the bellhousing/ flat plate on the back of the midsection). Giving us an adjusted value on Gators to 1.8* or roughly 7.1-8.9* difference from factory

For reference since the Factory Subaru 5 speed case is not parallel, the bottom has roughly a 3* tail up slope if you are measuring from the rib on the bottom


The dip stick is located 22" from the back of the 818 transmissin and 5th gear is located 7" inwards from the back.
An 8* difference over 15" (distance from the dipstick to 5th gear) would give us a vertical difference of 2.09"
If you are at a level of .5" over the fill dot in racing state then I think 5th gear is nearly dry and is only being lubircated with the return feed of oil dumping on top of it.

It's a tricky thing to determine exactly how much extra fluid you need because if you add the full 2.09" to keep 5th gear at a factory level then the front diff and 1st gear will be nearly completley submerged.

My recomendation would be to add enough fluid so that you are 1.5" past the full mark in normal running (pumps on) state

[Rob T]

Thanks. What would you recommend for the six speeds?

[Hobby Racer]

...six speeds are not prone to the same issues because all of the important parts are located in the main body and receive a little more splash lubrication from driving around

This combined with the forced lubrication of the pre-08 6 speeds makes the 6MT very reliable and not prone to that issue.

I would still recommend a cooler though. Something like the one I put in. The pre-08 6 speeds are super easy to add a cooler to.

IMG_20200311_155114185.jpgIMG_20200311_155122528.jpg

I will be going to the track on July 15/16 to test out the new setup and will report back with temps and logs.

[Mitch Wright]

Don't know what I did different other than run just under 300hp and 265tq and running a Cusco 1.5 diff, running 3qts of fluid in the trans but I never saw the temps as high as some in my 5 speed with out a cooler and a lot of track miles.

[DanielsDM]

Gator: are you running a pump and cooler? Is your temp sensor in the oil or on the case?

[Sgt.Gator]

Yes on the pump and cooler. See my build thread for details. The temp sensor is in the cooler line. I've verified the temp sensor readings with the IR Thermometer. We are going to pull it out and verify it a pot of heated water though.

[Sgt.Gator]

This is a copy of a post I just made in my build thread:

I am happy to report that the transmission tail lowering worked! And not a little, I mean hugely. I ran multiple sessions all day, the hottest the tranny got was 189 degrees. I'm still at the track and will run thru another set of sessions tomorrow, but I'm very confidant now that the trans temp issue is solved.

The only change from the last track day was lowering the tail of the trans to approximately negative 1.6 degrees. I am amazed it made that much difference. I was skeptical this would work but based on Fate066's recommendation (Zach at ZF Design) we went for it and he was right.

Kudos to Fate066 of ZF Design for helping me work thru this issue, and kudos to Josh and Alec at Arcflash LLC in Bend for the fabrication work and sticking with me thru long days and nights of doing and redoing their work.

I consider this a must mod not just for the 818Rs being tracked but all 818s on the street too. I consider it a basic design fail that FF needs to address in the frames they are building now.

Here's the mount hanging below the diffuser. We are going to add a wedge shape around it to get the smooth flow back under the car.




Gator's doing the Happy Dance Tonight!

[Hobby Racer]

Gator, what's your angle at the face of the bell housing? Or on the flat surface on the top of the of the bell housing mount area of the block where the grounds attach? I'm curious to know since I raised my motor and lowered my trans mount (but not as much as you). My motor trans combo is dead flat, zero degrees, measured from the bell housing mounting surface where the grounds connect.

[DanielsDM]

That’s great that dropping the tail is a solution to the overheating issues. I really don’t want to drop mine that far if I can avoid it. On your original setup what was the “running” oil level with the pump on? I’m hoping to be able to run a pump and cooler and return the oil to the top of the case above 5 gear (like yours), maybe Y the return and have the other line drop the oil on top of the 1-4 cluster. I’m using a custom trans mount that is about 1” lower than the Subaru part. The “rib” on the case above 5th gear is sloped 1degree down towards the front relative to the chassis.

[Sgt.Gator]

That’s great that dropping the tail is a solution to the overheating issues. I really don’t want to drop mine that far if I can avoid it. On your original setup what was the “running” oil level with the pump on? I’m hoping to be able to run a pump and cooler and return the oil to the top of the case above 5 gear (like yours), maybe Y the return and have the other line drop the oil on top of the 1-4 cluster. I’m using a custom trans mount that is about 1” lower than the Subaru part. The “rib” on the case above 5th gear is sloped 1degree down towards the front relative to the chassis.

I'm not sure where it was with the pump on. Static in the shop we filled about 1 -1.5" over the F mark on the dipstick.
If you overfill the trans to get the oil high enough where the gears are, you put too much where the Ring & Pinion / Differential are located. They then beat the oil and heat it up, at the same time frothing it into a foam.

Have you watched any of Gayle Banks videos on differential gear case covers? Although not exactly specific to our transaxles, the concepts he discusses about overfilling and the action of oil in a differential are directly applicable.
I agree with him, there's a reason the OEMs design the fill holes in a differential at a specific height that also makes it very difficult to overfill a diff.

What's going on behind your stock diff cover?



As I watched the videos it dawned on me why we hadn't noted it quicker in the street driven 818s or even in my 8181R (licensed) when I drive it around Bend for testing.....at 0- 50 - 30 - 25 - 0 - 25- 55 mph stop and go the differential doesn't beat the oil at high enough speeds to induce a great deal of heat, and you slow and stop enough for the bubbles to get a chance to aerate out of suspension. But on a race track where the min speed is usually 35, with top speeds of 150 mph, the gear oil in an overfilled trans is getting whipped to death! You can see it in the clear diff video of what a 50mph diff is doing to a normal fill. Personally I think a 70 mph interstate cruise would be very damaging too, but so few builders have transmission temp sensors they don't realize it.

Gator, what's your angle at the face of the bell housing? Or on the flat surface on the top of the of the bell housing mount area of the block where the grounds attach? I'm curious to know since I raised my motor and lowered my trans mount (but not as much as you). My motor trans combo is dead flat, zero degrees, measured from the bell housing mounting surface where the grounds connect.

My car is in the trailer until Saturday, I'll get that info for you then.

[Sgt.Gator]

And a bit repetitive to the above but has temp test data on a dyno:

How to Engineer the PERFECT Differential Cover


Note the 50 mph test at 9 mins in the video. Now imagine 100 mph on a race track with an overfilled transaxle / diff!

[DanielsDM]

Very good info Gator. Thanks for sharing.

[Hobby Racer]

Another data point. Ran two full days at Waktins Glen and the trans temps never topped 195F. I have a 6 speed with an external cooler setup with air from the side scoop forced through the cooler. The temps were monitored with a sensor logged via the ECU.

[Canadian818]

Anyone know what angle the transmission sits at normally as FFR designed on the rear block off plate? I'm not 100% clear what "rib" everyone is measuring from and I have the older style 5mt with the newer style center housing so I'm not sure I have the same rib or not. Measuring off the rear block off plate, my trans is angled up 2 degrees.

[Sgt.Gator]

Anyone know what angle the transmission sits at normally as FFR designed on the rear block off plate? I'm not 100% clear what "rib" everyone is measuring from and I have the older style 5mt with the newer style center housing so I'm not sure I have the same rib or not. Measuring off the rear block off plate, my trans is angled up 2 degrees.

We measured off the angle on the backplate of my 5 speed. It's pretty detailed out in my build thread, start at this post:

https://thefactoryfiveforum.com/show...l=1#post417204

When you see the pic you'll see the problem with the FFR designed tranny mount.

[Santiago]

Just out of curiosity, do you guys think (or does anyone know) if the angle of the trans' rear block off plate is parallel to the bell housing flange...which should be at a right angle to the crank center line?

I ask mostly because I measured about 3.25 deg nose down (tail up) off of the crank boss. That seems to fall pretty close in line with what others reported as the FFR angle (assuming this is parallel to the rear block off plate).

[Sgt.Gator]

Just out of curiosity, do you guys think (or does anyone know) if the angle of the trans' rear block off plate is parallel to the bell housing flange...which should be at a right angle to the crank center line?

I ask mostly because I measured about 3.25 deg nose down (tail up) off of the crank boss. That seems to fall pretty close in line with what others reported as the FFR angle (assuming this is parallel to the rear block off plate).

I'm sure fateo66 can answer these questions about backplate angles since he build/rebuilds both the 5 and 6 speed versions as 818 trannys, but he doesn't visit here often, you may want to PM him. He is Post #5 above.

[Sgt.Gator]

Quick Update: I spent all day at Oregon Raceway Park today, 5 sessions. Trans temps averaged 145. Never went over 155. It was pretty cool today though.