Straight thread sealant for tranny cooler lines

Messages
3
Location
Carnation, WA
Hello,

possible unique situation here needing advice... long time lurker..

I have an ZF8HP70 transmission (2015 Ram 1500 8speed tranny) that has been swapped into a Jeep Wrangler along with the 5.7hemi. Long story short it all fits and works great with one exception. Part of the conversion is to remove the factory heat exchanger that bolts to the side of the tranny and uses floating inserts sealed with O rings. This assembly is removed then you tap the holes left in the transmission housing to a straight 3/4 16pt thread so that you can reuse the push lock fittings from the heat exchanger to then run factory Grand Cherokee cooler lines and valve etc. sounds simple enough however the fittings to not seat far enough into the housing to allow the O rings to contact let alone seal anything and only one hole is beveled to not cut the o ring anyway. So the common practice is to use a thread sealant to provide the seal. I naively went to the cabinet and grabbed my Permatex Hi temp thread sealer, applied it and went on my way continuing the swap. Well that did not seal and I have a substantial leak after one heat cycle. transmission case is aluminum as are the fittings And again are straight cut. I am taking it apart today to see if anything can be done to utilize the preferred o ring sealing method but am reaching out here for any advice on sealant(or any other obvious thing I missed).
I have a tube of Loctite 565 but am concerned I will have the same issue and while it sounds crude, improper I am considering RTVing (possibly Permatex Aviation...) these in or going to the drastic measure of epoxy if all else fails. Picture of actual parts for reference

thanks in advance for any advice, feedback. And FYI I have searched here and the net but have not found my situation, straight cut threads, aluminum on aluminum and tranny fluid.

D472B03E-31E9-492F-B4E5-5A37A2FA074C.jpeg
 
Messages
3,649
Location
Roanoke Virginia
Thanks for the reply, I used liquid Permatex.
May want to use some Red RTV it’s high temperature or Black. Usually don’t have issues from the liquid thread sealant I used that to bypass the transmission cooler on my dads truck and it worked fine it holds the lines in still holds today 5 years later.
 
Messages
25,172
Location
MA, Mittelfranken.de
Hello,

possible unique situation here needing advice... long time lurker..

I have an ZF8HP70 transmission (2015 Ram 1500 8speed tranny) that has been swapped into a Jeep Wrangler along with the 5.7hemi. Long story short it all fits and works great with one exception. Part of the conversion is to remove the factory heat exchanger that bolts to the side of the tranny and uses floating inserts sealed with O rings. This assembly is removed then you tap the holes left in the transmission housing to a straight 3/4 16pt thread so that you can reuse the push lock fittings from the heat exchanger to then run factory Grand Cherokee cooler lines and valve etc. sounds simple enough however the fittings to not seat far enough into the housing to allow the O rings to contact let alone seal anything and only one hole is beveled to not cut the o ring anyway. So the common practice is to use a thread sealant to provide the seal. I naively went to the cabinet and grabbed my Permatex Hi temp thread sealer, applied it and went on my way continuing the swap. Well that did not seal and I have a substantial leak after one heat cycle. transmission case is aluminum as are the fittings And again are straight cut. I am taking it apart today to see if anything can be done to utilize the preferred o ring sealing method but am reaching out here for any advice on sealant(or any other obvious thing I missed).
I have a tube of Loctite 565 but am concerned I will have the same issue and while it sounds crude, improper I am considering RTVing (possibly Permatex Aviation...) these in or going to the drastic measure of epoxy if all else fails. Picture of actual parts for reference

thanks in advance for any advice, feedback. And FYI I have searched here and the net but have not found my situation, straight cut threads, aluminum on aluminum and tranny fluid.

View attachment 34673

If you grind the thread make darn sure they start easy in the aluminum case, you don't want to bugger those. Someone may possibly make a shorter one like this example (no idea what thread size yours has just an example).


 

wADVr

Thread starter
Messages
3
Location
Carnation, WA
thank your the reply’s. I am tapping the holes with a bottom tap this go around which may allow the fittings to seat properly with the o rings or possibly crush washer(thanks for that idea). I used a plug tap which didn’t allow the fitting to seat before bottoming out on the threads. Will see if those couple more threads do the trick.

depending on how that goes I guess will determine how important the thread sealant is. I can cut the fitting and chase the threads back out but hope I don’t need to.
 
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