nomercy346
Member
My truck's trans was always running kinda hot for my liking (195 under normal cruising) and I read quite a few posts on how this was supposedly normal. Then last summer I noticed it always continually creeping higher after a while of driving, approaching 200+ deg.
I started reading the forums and determined it to be the thermal bypass valve (TBV) on the side of the trans. Under normal driving conditions with cold ambient temps and during warmup, these transmissions are actually being heated by the engine coolant. The fluid is only being cooled when it really needs to be to save on friction and emissions.
There is a heater core on the side of the trans with a thermostat inside that regulates the amount of fluid going to the trans cooler and how much is being heated. Apparently these can go bad and as happened with mine are permanently heating the fluid.
The TBV is actually not that expensive to buy but the replacement is a major PITA. I originally bought a new one last fall but rounded off a torx bolt during the DIY (actually on the easy part of this DIY, haha) and put off the job until now as it wasn't an issue during winter and spring with cooler outside temps and never went over 200 deg anymore. Over the last couple weeks, though, in 80-90 deg weather, I could only drive 20-30 mi max before the trans was approaching 210 deg and I had to let it cool down.
So after finally getting that bolt out, I replaced the thing in my garage today, and it seems like it did the trick. Took it for a test drive and it never went over 185 deg anymore. Hope it's fixed for good. So, if you're seeing higher temps with your truck, consider replacing the TBV.
Parts needed:
Mopar P/N 52014750AE - heater assembly
1 qt ATF for the 8 speed
Tools needed:
- torx 40 or 45 cant remember
- allen key 8 mm
- bunch of common sockets and ratchets
- fexible hose pliers
- hose pinch pliers
- pick
- drain pan
- fluid pump for ATF
- torque wrench
DIY Procedure
1. take off the front driveshaft if you have a 4x4. Impact gun makes this much easier as you can't get to all the bolts at once and you'll need to switch it between 2wd and 4wd to rotate the shaft and break the bolts loose respectively
Mark the pinion to the shaft if you want to install it the way it was when you put it back together, shouldn't really matter though.
Now we're removing the brackets off the coolant and trans fluid lines to get some slack and wiggle room when removing the heater assembly later.
2. remove the shifter cable - pulls right off that lever and unclips from the bracket
3. remove the shifter cable bracket and cooler line bracket on the driver side (held on by the same two bolts) - these are T40 or T45 torx from the factory and they were really hard to break loose on my truck, may have Loctite on them as well and they're steel bolts in an aluminum casing so kinda tricky. Make sure to get a good grip on it as its also a tight fit for your hands. I didn't and rounded off the top one resulting in a huge headache. I eventually cut the shifter bracket and bought a new one just to be able to create a situation that loosely resembles accessability
Replaced them with the regular hex bolts you see in the photo...
4. there is a bracket that holds the coolant lines in place on top of the trans on the pass side, unbolt it.
5. there are two brackets on the lower part of the trans on the pass side. one for the coolant one for ATF - unbolt both of them
Now the fun part starts. There is VERY little room for your hands so it takes some patience to remove the coolant hoses and tranny lines on top of the heater assembly. Make sure you wear safety glasses as there will be fluid spilling right on top of you.
6. I started with pinching the coolant hoses. If you don't do this, I would expect all the coolant to drain out of the truck once you remove the hoses. The FSM actually states to drain all coolant first. So make sure to pinch them tight.
7. To remove the clamps off the coolant hoses you'll need flexible hose clamp pliers, there's no way around these IMO. Even with them it was tricky cause some of the clamps are oriented in a way that makes it super hard to get the tool on. I actually removed the front hose last, after I had the whole assembly loose.
Some coolant will leak out of the heater, once you remove the hoses - about half a quart. So make sure you have a pan ready.
8. This is where I removed the 3 bolts holding the heater itself. Once it's off you'll have more wiggle room to get to the hoses and lines.
ATF will come out the heater once you slide it out of the trans - slightly less than half a quart for me.
9. Disconnect the trans cooler lines. Slide the plastic cover off the connector first. I used a small pick to remove the little metal retainers. Also takes patience as you can hardly see them from below, let alone reach them. Once the retainer comes off, the lines will slide right out the top. The retainers also fly off into oblivion pretty easily, but the new assembly comes with them so you won't need to look for them if they're gone…
10. clean everything up
11. connect the hoses and lines to the new assembly. I started with the front hose, then the cooler lines and the rear hose last.
12. bolt the heater to the trans, the new part had slightly different rubber grommets where it goes into the trans. The old part had little metal fittings with o-rings. These were apparently common to leak.
13. secure all the brackets you removed in the beginning.
14. put the shifter cable back in place.
15. bolt the driveshaft back on (85 lb-ft)
16. refill trans
Here's how I did it, there are quite a few how to's on this all over the web:
Apparently you're supposed to have either the trans itself or the trucks frame level, seems to be kind of a debate.
I tried both, getting the trans level you'll have to jack the back of the truck up more than 3 feet, seemed pretty sketch.
Having the frame level (which is what the FSM says and makes the most sense to me as that is what happens when you put it on a hoist at the dealer) you'll need to jack the front a couple inches.
- Make sure trans temp is below 80 deg.
- start the truck
- remove the fill plug and pump in ATF until it spills out
- insert plug
- go into reverse for 5 s
- go into drive for 5s
- you need the rear wheels off the ground and the truck in 2wd for this! best only attempt with truck on hoist - let off brake and accelerate to 2nd gear, keep it there for 5s - I skipped this step as I did not have the rear wheels off the ground, I put back almost exactly as much fluid as I caught coming out, seems like it didn't matter that much
- go into neutral, rev to 2k for 5s
- put it back in park
- make sure the temp is still below 120 deg
- remove fill plug and let excess drip into pan
- tighten fill plug
17. enjoy your cool running trans
18. crack a cold one
You should probably bleed the cooling system but I couldn't find how and I figured half a quart could be replaced sometime by just topping off the expansion tank?
I started reading the forums and determined it to be the thermal bypass valve (TBV) on the side of the trans. Under normal driving conditions with cold ambient temps and during warmup, these transmissions are actually being heated by the engine coolant. The fluid is only being cooled when it really needs to be to save on friction and emissions.
There is a heater core on the side of the trans with a thermostat inside that regulates the amount of fluid going to the trans cooler and how much is being heated. Apparently these can go bad and as happened with mine are permanently heating the fluid.
The TBV is actually not that expensive to buy but the replacement is a major PITA. I originally bought a new one last fall but rounded off a torx bolt during the DIY (actually on the easy part of this DIY, haha) and put off the job until now as it wasn't an issue during winter and spring with cooler outside temps and never went over 200 deg anymore. Over the last couple weeks, though, in 80-90 deg weather, I could only drive 20-30 mi max before the trans was approaching 210 deg and I had to let it cool down.
So after finally getting that bolt out, I replaced the thing in my garage today, and it seems like it did the trick. Took it for a test drive and it never went over 185 deg anymore. Hope it's fixed for good. So, if you're seeing higher temps with your truck, consider replacing the TBV.
Parts needed:
Mopar P/N 52014750AE - heater assembly
1 qt ATF for the 8 speed
Tools needed:
- torx 40 or 45 cant remember
- allen key 8 mm
- bunch of common sockets and ratchets
- fexible hose pliers
- hose pinch pliers
- pick
- drain pan
- fluid pump for ATF
- torque wrench
DIY Procedure
1. take off the front driveshaft if you have a 4x4. Impact gun makes this much easier as you can't get to all the bolts at once and you'll need to switch it between 2wd and 4wd to rotate the shaft and break the bolts loose respectively
Mark the pinion to the shaft if you want to install it the way it was when you put it back together, shouldn't really matter though.
Now we're removing the brackets off the coolant and trans fluid lines to get some slack and wiggle room when removing the heater assembly later.
2. remove the shifter cable - pulls right off that lever and unclips from the bracket
3. remove the shifter cable bracket and cooler line bracket on the driver side (held on by the same two bolts) - these are T40 or T45 torx from the factory and they were really hard to break loose on my truck, may have Loctite on them as well and they're steel bolts in an aluminum casing so kinda tricky. Make sure to get a good grip on it as its also a tight fit for your hands. I didn't and rounded off the top one resulting in a huge headache. I eventually cut the shifter bracket and bought a new one just to be able to create a situation that loosely resembles accessability
Replaced them with the regular hex bolts you see in the photo...4. there is a bracket that holds the coolant lines in place on top of the trans on the pass side, unbolt it.
5. there are two brackets on the lower part of the trans on the pass side. one for the coolant one for ATF - unbolt both of them
Now the fun part starts. There is VERY little room for your hands so it takes some patience to remove the coolant hoses and tranny lines on top of the heater assembly. Make sure you wear safety glasses as there will be fluid spilling right on top of you.
6. I started with pinching the coolant hoses. If you don't do this, I would expect all the coolant to drain out of the truck once you remove the hoses. The FSM actually states to drain all coolant first. So make sure to pinch them tight.
7. To remove the clamps off the coolant hoses you'll need flexible hose clamp pliers, there's no way around these IMO. Even with them it was tricky cause some of the clamps are oriented in a way that makes it super hard to get the tool on. I actually removed the front hose last, after I had the whole assembly loose.
Some coolant will leak out of the heater, once you remove the hoses - about half a quart. So make sure you have a pan ready.
8. This is where I removed the 3 bolts holding the heater itself. Once it's off you'll have more wiggle room to get to the hoses and lines.
ATF will come out the heater once you slide it out of the trans - slightly less than half a quart for me.
9. Disconnect the trans cooler lines. Slide the plastic cover off the connector first. I used a small pick to remove the little metal retainers. Also takes patience as you can hardly see them from below, let alone reach them. Once the retainer comes off, the lines will slide right out the top. The retainers also fly off into oblivion pretty easily, but the new assembly comes with them so you won't need to look for them if they're gone…
10. clean everything up
11. connect the hoses and lines to the new assembly. I started with the front hose, then the cooler lines and the rear hose last.
12. bolt the heater to the trans, the new part had slightly different rubber grommets where it goes into the trans. The old part had little metal fittings with o-rings. These were apparently common to leak.
13. secure all the brackets you removed in the beginning.
14. put the shifter cable back in place.
15. bolt the driveshaft back on (85 lb-ft)
16. refill trans
Here's how I did it, there are quite a few how to's on this all over the web:
Apparently you're supposed to have either the trans itself or the trucks frame level, seems to be kind of a debate.
I tried both, getting the trans level you'll have to jack the back of the truck up more than 3 feet, seemed pretty sketch.
Having the frame level (which is what the FSM says and makes the most sense to me as that is what happens when you put it on a hoist at the dealer) you'll need to jack the front a couple inches.
- Make sure trans temp is below 80 deg.
- start the truck
- remove the fill plug and pump in ATF until it spills out
- insert plug
- go into reverse for 5 s
- go into drive for 5s
- you need the rear wheels off the ground and the truck in 2wd for this! best only attempt with truck on hoist - let off brake and accelerate to 2nd gear, keep it there for 5s - I skipped this step as I did not have the rear wheels off the ground, I put back almost exactly as much fluid as I caught coming out, seems like it didn't matter that much
- go into neutral, rev to 2k for 5s
- put it back in park
- make sure the temp is still below 120 deg
- remove fill plug and let excess drip into pan
- tighten fill plug
17. enjoy your cool running trans
18. crack a cold one
You should probably bleed the cooling system but I couldn't find how and I figured half a quart could be replaced sometime by just topping off the expansion tank?
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