Transmission thermostat bypass failures?

[BlkZrx]

I put the bypass on my 4th generation 6 speed, it runs 30 to 50 degrees cooler. I received some feedback from an "expert" that it's bad for my transmission. Has anyone had issues?

 

[crazykid1994]

Lots of experts say it’s bad. Lots of experts say it’s better for transmission life long term if they run cooler. Really depends on who you talk to. Part of it is moisture control in the oil. So as long as you are doing proper maintenance and changing the oil at the appropriate time you should be good. It’ll help prevent burning the clutches and helps line pressure stay up due to the oil not thinning out from heat.

 

[mtnrider]

I've never been sold on the bypass myself. I'd rather have it get up to temp where it is running efficiently, but that's just my opinion.
The whole reason behind the bypass was supposedly the thermostat "could" fail and cause it to over heat but to be honest I don't think I've seen a single one fail (I'm sure there are a few out there like any part).


.

 

[quickster2]

I've never been sold on the bypass myself. I'd rather have it get up to temp where it is running efficiently, but that's just my opinion.
The whole reason behind the bypass was supposedly the thermostat "could" fail and cause it to over heat but to be honest I don't think I've seen a single one fail (I'm sure there are a few out there like any part).


.

My trans barely moves off of 172 no matter the load. The tranny and the fluid is designed to operate in this temp range. Many of these "mods" are unnecessary. If they make you sleep better at night than great.

 

[SouthTexan]

The thermostat got stuck in my brother's 2014. Temps kept getting hotter than normal when towing. We took the valve off and the spring was stuck in the up positioned which meant no fluid was going to the trans cooler like it was suppose to. We both replaced ours with an open valve with no thermostat spring in it that can fail.

A ram trans engineer on the Turbo Diesel Register stated that the only reason why the valve is mainly for fuel economy reasons to get the trans temps up quicker. I will gladly sacrifice a little fuel economy to remove a failure point. I would hate to be towing my RV a long distance from home and have that thermal bypass fail like it did in my brother's truck.

A lot of people do many things that I think are unnecessary(like changing oil way too soon) just for piece of mind and I don't see this as any different. Although in my case, my trans is not stock and neither is my engine. I am putting out way more power than stock and my transmission's line pressure is considerably more than stock which creates more heat that the fluid has to shed. So I can see this as a good supporting mod if your truck is not stock.

 

[GsRAM]

I put the bypass on my 4th generation 6 speed, it runs 30 to 50 degrees cooler. I received some feedback from an "expert" that it's bad for my transmission. Has anyone had issues?

I have had zero issues since installing mine. The #1 killer of automatic transmissions is heat. Keep the fluid cooler and they will run longer. If that bypass/thermostat sticks closed and cuts the transmission cooler out of the circuit, the transmission is toast. As said, service it regularly (I do all of my automatics every 5 yrs or 30k miles whichever comes first). I just did service mine last month for the first time at nearly the 5yr mark (15,600 miles)

I think the bypass was likely EPA driven to squeeze every bit of mpg out of vehicles these days that it can.

Just my two cents though...to each their own.

 

[Wild one]

Up till 2012 none of the 1500's had a transmission thermostat.Only after FCA adopted their thermal management policy in 2013 did they start implementing the transmission thermostat to meet their epa corporate milege numbers.Just food for thought

 

[68PowerWagon]

I wasn't as concerned with the part failing as I was how much of a restriction there was, even with the valve open. I think someone took the time to figure it out & it was like 64% reduction in flow when open. After I removed mine I could see how that number is real. The hole for the fluid to go through was a fraction of the size of your transmission lines. While towing I was getting in the low 200's which won't immediately kill a transmission, but I think at that point you are shortening it's life. To answer your question, no I have not had any problems what so ever after installing the bypass. I have put about 30k on since the mod.

 

[DodgeDude1999]

I've never been sold on the bypass myself. I'd rather have it get up to temp where it is running efficiently, but that's just my opinion.
The whole reason behind the bypass was supposedly the thermostat "could" fail and cause it to over heat but to be honest I don't think I've seen a single one fail (I'm sure there are a few out there like any part).


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The check valve in the 2nd gens is why the trans in those trucks got a bad rap. The check valve would gum up and stick closed, trans would overheat

Same thing can happen with the block.

My truck hit 220 stuck in traffic a few summers back.
My inlaws have a place near Kalamazoo (I’m in the burbs of Chicago ), with the block temps would be 170-180 on the highway, after block delete 130-135.

Now with the trans tunes, it will see 140-150.

 

[DodgeDude1999]

I have had zero issues since installing mine. The #1 killer of automatic transmissions is heat. Keep the fluid cooler and they will run longer. If that bypass/thermostat sticks closed and cuts the transmission cooler out of the circuit, the transmission is toast. As said, service it regularly (I do all of my automatics every 5 yrs or 30k miles whichever comes first). I just did service mine last month for the first time at nearly the 5yr mark (15,600 miles)

I think the bypass was likely EPA driven to squeeze every bit of mpg out of vehicles these days that it can.

Just my two cents though...to each their own.

The thermostat block was because of emissions. With the fluid warmer it’s easier to pump and the engine has to work less.

 

[aanorm69]

I pull a 13k 5th wheel and before replacing the OEM block trans would run 200-210 F on the highway.
With the valveless block trans rarely gets over 175 F even in 95 deg summer driving.
(68RFE 6-speed)

 

[HEMIMANN]

OP - let me pose it to you a different way - what were the durability of transmissions prior to adding a thermostat?

None? Right, I thought so. Remember why they did this - to get an infinitesimal increase in fuel economy - while shortening the oil and transmission life from heat in the summertime!!!

Transmissions don't die from cold - they die from heat! (oxidation, varnish, orifice plugging)

 

[mtofell]

I pull a 13k 5th wheel and before replacing the OEM block trans would run 200-210 F on the highway.
With the valveless block trans rarely gets over 175 F even in 95 deg summer driving.
(68RFE 6-speed)

This is when it's needed - if you're not maxing things out I wouldn't bother.

 

[KLook]

This is when it's needed - if you're not maxing things out I wouldn't bother.

In other words, soccer moms need not apply. But almost everyone else should.....

 

[quickster2]

I pull a 13k 5th wheel and before replacing the OEM block trans would run 200-210 F on the highway.
With the valveless block trans rarely gets over 175 F even in 95 deg summer driving.
(68RFE 6-speed)

That's interesting. I pull around 13K+ once a year for 500 miles from Michigan to KY every August. Have seen several 90+ degree trips. Never have I seen the temps you are seeing. I wonder if your frontal area has that effect? My trip is with my tractor & implements on a 25" gooseneck. I guess if I saw those temps I might consider something different. I'll see my oil temp climb to around 212 through the long hills in KY but not the trans. I do put the trans in tow haul mode going up those hills.

 

[SouthTexan]

That's interesting. I pull around 13K+ once a year for 500 miles from Michigan to KY every August. Have seen several 90+ degree trips. Never have I seen the temps you are seeing. I wonder if your frontal area has that effect? My trip is with my tractor & implements on a 25" gooseneck. I guess if I saw those temps I might consider something different. I'll see my oil temp climb to around 212 through the long hills in KY but not the trans. I do put the trans in tow haul mode going up those hills.

The 66 and 68RFE aren't exactly the same. The back half is about the same with the same planetary gear set, but the front half is not.

From a Ram trans engineer.

"The 68RFE is a completely different geartrain than the 545RFE/65RFE, with different ratios and is a true 6-speed. It has a different case (to mate to the 6.7L Cummins engine), a larger-capacity pump, and higher-capacity clutch packs. So it is whole different animal, although still similar in some respects.

The 66RFE is kind of a hybrid between the two. It uses the same case as the 545RFE/65RFE (in order to mate to the gas engine). It uses the same pump, and similar input clutches, to the 545RFE/65RFE, but in 2014 and later has greater heat sink capacity in the OD clutch. The key feature, though, is that the 66RFE uses the same geartrain (and ratios) as the 68RFE, so it again is a true 6-speed."

 

[Ramster1]

As to replacing the trans bypass unit. After removal if you look inside the thermostat side of the bypass. You’ll see that not only does it divert the transmission fluid flow, but it also restricts the flow down to three eights from half-inch size line to and from your cooler. All in all this is just a nuisance device, Strictly to increase the fuel economy on these trucks by lowering the viscosity of the trans fluid. In addition to removing the bypass I added a 4.5 quart deep trans pan. Very happy with my results.

 

[SouthTexan]

I pull a 13k 5th wheel and before replacing the OEM block trans would run 200-210 F on the highway.
With the valveless block trans rarely gets over 175 F even in 95 deg summer driving.
(68RFE 6-speed)

Same here. I pull a 13.5k 5ver 160 miles to the cost late spring and back again late summer. Temps would start to creep up especially on the late summer tow with temps in the 100s.

 

[Senodil]

2018 68RFE wihich currently has over 50K with the bypass and truck runs much cooler. 130-140 in Florida daily driving & trips, but I do notice it can hit up to 170 in heavy slow traffic. I did initial fluid change at 50K, and every 25-30 after that... cheap insurance.

 

[DanEddy]

The stock trans thermostat is set for 168 degrees, not bad if it stayed there but when towing in hills or mountains it gets far too hot, like up to 220. Once you're out of the hills it doesn't cool down quickly at all and as anyone knows heat is the kiss of death for a transmission. If you have the 68RFE trans, you have a double whammy as it won't last long with heat.

I've replaced the thermostat and put in the bypass unit as well as a secondary B&M trans cooler with a thermostatic fan on it as I do tow. My trans did fail at 97,000 miles and had it rebuilt to a Stage II level, it runs on a normal day at about 140 degrees and when towing it now never gets to 220, it stays cooler and when it does warm up and I get out of the hiills it cools back down much faster.

Here's another plus to the bypass, you can now fully flush out your trans fluid when it's time the change fluide. If you have the stock thermostat in the truck it blocks you from flushing the stock cooler when you drain fluid.