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Transmission Thermostat

17K views 38 replies 13 participants last post by  spewitt 
#1 ·
Got it installed today finally. Gets up to temp quickly and holds it. Does what it's supposed to, hopefully it will extend the life of the transmission.
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#3 ·
Can you provide a picture of where you mounted yours? Mine came in today and I'm going to try to install it tomorrow. A location of where you choose to install it would be helpful.

To answer the question of why, I don't see the temp move on mine at all, unless it's towing or idling for an extended period of time. I would like for the trans to warm up at least a bit on my non towing days.

Stay frosty
 
#4 ·
Can you provide a picture of where you mounted yours? Mine came in today and I'm going to try to install it tomorrow. A location of where you choose to install it would be helpful.

To answer the question of why, I don't see the temp move on mine at all, unless it's towing or idling for an extended period of time. I would like for the trans to warm up at least a bit on my non towing days.

Stay frosty
Are you watching the factory "guage"? If so that's your problem. I use a scan guage 2 and mine warms up to 170* just daily city driving.
 
#5 ·
First, I have no problem with owners doing whatever they want to their vehicles, it's yours, mess with it I'd you want.

2nd, don't be surprised and be all angry if or when something breaks or fails because of modifications (like cv boots tearing on lifted trucks, for example) and it is just plain dishonest to remove what you did, reflash the ecu or whatever, then drag it to the dealership and want them to pay for repairs under warranty.

3rd, the stock dash gauge just isn't very refined in it's reporting of temperature, and I suspect they have the display calibrated to higher temps because they figured most drivers would be working it hard enough to have a pretty warm transmission. The gauge might not show or just barely be showing a trans tempt but that doesn't mean it is too cold, in fact an OBDII scanner will indicate the trans temp is at a normal spec operating temp.

4th, you have to admit, this is a pretty good looking install and the part appears to be reasonably robust.

Finally, some owners have felt that they can get smoother shifts and what they feel is better trans behaviours by forcing it to run hotter, and if they feel like their experience warrants the hotter thermostat then let them. Vehicle owners have a long history of messing with factory equipment to get vehicles to act they way the owners think they should.

That being said, my personal experience with this truck is different and I have no reason to alter it's transmission cooling system. I also don't want to have a transmission failure (not necessarily due to the alteration) and have to argue with the dealership about whether it could have caused a problem (although it isn't likely to have done so). The only other alternative, which makes me uncomfortable, is pulling a mod, and then presenting the truck for repairs without telling them what you had done to it (unless you plan on footing the bill yourself and not expecting the warranty to cover it).




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#6 ·
I could be mistaken about the logic and if i am someone with more knowledge can correct me but here goes. The thermostat will not make the tranny run hotter, it will get it up to temp quicker, that is all. I think about this modification for the simple fact i hate the way my truck shifts this time of year. The “flair/slip” on cold mornings is absolutely driving me nuts. Once the temp climbs to at least 90/100 degrees (scanguage) its a different ballgame. Warmer weather its 100% a non issue. So if you live in the warmer climates or have a pappy foot it wont make sense.
 
#8 ·
For reference, it is the exact opposite of you statement, the machine won't gain temperature any faster if you have a thermostat with a higher set point, it just doesn't open until the temp reaches the higher setting.

Think of it this way, if you open a faucet and it starts filling a bucket, and it normally has a hole that starts letting water out at 160 ml, but you plug that hole and drill one higher up so it doesn't spill out until there is 175 ml in the bucket, that doesn't effect how fast it fills from 0 to 100 ml, same faucet same rate of water into the bucket same time to rise from empty to 100 ml.

In simplistic terms the primary factors in how fast the system warms from ambient to your min goal of 100 degrees is how cold the motor/trans are at start and how cold ambient air temp is (as this dictates how quickly heat is lost). The hotter thermostat only effects how much hotter it allows the system to maintain itself. Thus the decision to be made is whether you feel like the transmission should run hotter all the time and whether you think that it works better being at the higher temp all the time instead of the lower stock temp.

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#7 ·
Lots of comments, I like good conversation so I will tell you the "why" as well as clear up some misconceptions.

1. I don't use just the factory gauge. I have the EZLYNK as well as a trans temp gauge i mounted on the dash (electrical gauge).

2. The Aisin is an HD application that is honestly overkill for this truck, which is why I like it. In addition, there are two transmission coolers on this truck from the factory. This leads to the problem and the "why" I did this...

3. The transmission would rarely get above 120 degrees during normal operation and would barely hit 140-150 when towing heavy unless I was really loading it up like up a hill or in heavy traffic. Even then it never broke 170 or so. The ideal temp for an automatic transmission to operate at peak efficiency is 170-180. You want to see at least 140 when the truck is warm. If the transmission temperature routinely operates "cold" it's nearly as bad as running too hot all the time. The fluid doesn't function the way it's supposed to, it never gets to the proper viscosity, and the engine works harder to spin the transmission all the time because of the thicker than intended fluid. Transmission oil, just like engine oil, is designed to operate within a specific temperature range. Running outside that range all the time on either end of the spectrum is bad for longevity and proper functionality. My trans, like many others with the Aisin, was never running warm enough to function properly. A solution promoted by Josh Chapman and others within the community was a thermostat that allows the temp to maintain a proper operating temperature. Every modification I do is designed around longevity and increased efficiency, which also yields better performance as a byproduct.

As to the comment about expecting the dealership to fix problem induced by modifications, I think anyone who has dealt with Nissan or any dealership knows they won't do it. That being said, any flaws that are inherent in the design (or a defect from the manufacturer) is a different story and I 100% expect those to be covered. Outside of that, I don't let dealerships touch any vehicle I own. I do all my own work on all my vehicles. If something breaks that I caused, I fix it myself with no complaints.

I think I covered it all, but please ask if there are more questions. I'm not trying to sell the product, I just like to show projects I do so others can see solutions for certain issues or just know what's possible.
 
#18 ·
Does yours also have a weird "false shift" in second around 1600-1800 rpm while accelerating? When mine goes into 2, it doesn't seem like it goes in all the way, and then goes the rest of the way (and not very nicely) around that engine speed. Doesn't matter how hard the acceleration is...

I also get a shift flare from 3-4 but only if the trans temperature is below 100F... something magical happens at 100F that stops it - TCU program changes or something.

And, under load I get some kind of race shifting between 4 and 5 in either direction... it sounds like the motor runs away but only for a split second. Not sure if it's actually the motor (don't see anything on the tach) or if it's something in the trans.

Dealer claims it's all "normal," of course... No CEL, no problem.

Anyway I've thought of installing one of these to try to get better behavior out of the trans.
 
#14 ·
So a quick update. I took it for a drive today to do some comparisons.

1. For those that say the in dash gauges are junk, not true. They just only register within a specific range. They do respond a little slow compared to reading it with an OBD reader, such as EZLYNK or ScanGauge. The trans temp doesn't begin to register on the factory bar graph until 110°. After that, each tick mark is 15°. The center of the gauge would be 170°, which makes sense as that is the ideal trans fluid temp.

2. This morning it was cold, about 33-38° during my test drive. As a result, the temp still took a little bit of time to get up. It took about 7 minutes to break 100° and 8 minutes to break 110° and register on the factory gauge. Before it wouldn't have registered at any point with no load at this temperature.

3. Temps got to 152-156° and held steady in that range regardless of load. At idle it would drop to 152, but go up to 154-156 when moving.

4. The biggest difference I noticed driving was no shift flare at all when warm (I would get it occasionally before, nothing serious) and much better and crisper downshifting when slowing down or when hammering the go pedal. The improvement in downshifts is very noticeable.

We will see what happens long term,, especially when towing my fifth wheel, but overall I am so far happy with it. Relatively inexpensive and easy for a DIY project.
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#31 ·
So a quick update. I took it for a drive today to do some comparisons.

1. For those that say the in dash gauges are junk, not true. They just only register within a specific range. They do respond a little slow compared to reading it with an OBD reader, such as EZLYNK or ScanGauge. The trans temp doesn't begin to register on the factory bar graph until 110°. After that, each tick mark is 15°. The center of the gauge would be 170°, which makes sense as that is the ideal trans fluid temp.

2. This morning it was cold, about 33-38° during my test drive. As a result, the temp still took a little bit of time to get up. It took about 7 minutes to break 100° and 8 minutes to break 110° and register on the factory gauge. Before it wouldn't have registered at any point with no load at this temperature.

3. Temps got to 152-156° and held steady in that range regardless of load. At idle it would drop to 152, but go up to 154-156 when moving.

4. The biggest difference I noticed driving was no shift flare at all when warm (I would get it occasionally before, nothing serious) and much better and crisper downshifting when slowing down or when hammering the go pedal. The improvement in downshifts is very noticeable.

We will see what happens long term,, especially when towing my fifth wheel, but overall I am so far happy with it. Relatively inexpensive and easy for a DIY project. View attachment 44121
If you don't mind me asking, what are you using to display those gauges on you Phoenix radio?
 
#16 ·
This type of thermostat seems to be better suited to something like Oil to Air (OTA) cooling only. In the early 99 7.3 Powerstrokes, they were using only a 9 Row OTA cooler for the transmission with no trans fluid cooling through the radiator. It was a lousy setup, overheating transmissions when it was hot with heavy but within rated loads and over cooling when cold. Ford rectified it for the 2000 model year with proper radiator cooling lines. Upgrading to a 26 row 6.0 OTA cooler solved the overheating problem but aggravated over cooling. Anything below 40 degrees ambient was not going to warm the trans up. For many that knew of the problem, short of converting to radiator cooling lines for ~$1200, a device such as this for ~$40-$50 was the solution. It allowed the transmission to reach operating temp 170 and opened for cooling when it exceeded that.
 
#29 ·
Well, since it went a little off topic I will give a quick update lol (nice Iverson reference BTW). After driving back and forth to work a couple of days some observations...

1. When cold (outside ambient temp), it still takes a bit to warm up, but it does so steadily until hitting 156 or so. I have not seen a temp above 156 yet.

2. As I noted before, the shifting is more agressive, particularly the downshifting. Its almost, but not quite, as aggressive to downshift as when in tow mode. If I start coasting and tap the brake, it downshifts right away. It did not do that before and it is a pleasant surprise. When accelerating, it downshifts quicker as well.

3. The upshifting is a little strange. It does so positively, but seems to be hunting a bit for the gear. Not flaring, hard to describe. I think the transmission is having to learn again as the fluid is thinner when warm and consequently more line pressure is needed quicker to engage the gears fully. It isnt a problem, just noticeable.

After a couple of weeks I will see how it all shakes out. Overall I think it was a worthwhile investment.
 
#30 ·
I was thinking the same thing. The trans now has to relearn because this is something new, but I expect it to learn and smooth out within 7-10 days. I'll keep posting data from my end as time goes on. So far, I'm really enjoying this upgrade/mod.

Stay frosty
 
#37 ·
Really enjoy having one. Mad I didn't get one earlier. Trans shifts smooth now, up & down. Gets to temp fast and holds it. I occasionally get a flair, I may opt for a higher temp, but GA summers are pretty stupid and I'll make my mind up after this upcoming summer.

Stay frosty
 
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