360 thrust bearing failing at 1000 miles

[mjdriver]

Cooler line pressure results

Both coolers - 50psi cold idle

Radiator heat exchanger only - 50psi cold idle

Lines looped - 30psi cold idle

Lines looped stall test - 60psi cold , (tires breaking free)

Pressure started dropping as fluid warmed up.

What is normal? I'm thinking 20 psi diffence is unacceptable, I doubt the heat sink style cooler alone would be enough, so I'm thinking a decent air to air cooler should work, would a parts store one be ok or should I get something high dollar?

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[sansabarJ]

Stop !! Ok your pressure is as I had said in my first post too high. 30 psi on hard acceleration is a max reading , the highest you would want to see ok ? At idle in drive , foot on the brake not moving , you should have about 10 to 15 PSI . 60 PSI is TOO MUCH PRESSURE and going to ruin your thrust bearing as it did before . Ok so do this test now , bypass both coolers, run a piece of power steering return hose hose between the lines and double clamp . Don't use fuel hose it cannot take much pressure .Run the Jeep and then see what your gauge reads now . I suspect it will be the same readings and very high . Remember it takes no time to damage that thrust at over 30 PSI . If you still have too much pressure , get rid of the special converter and get an original stock unit . Save yourself the aggravation . Your coolers should not cause any pressure build up unless they have some unusual restriction in them . In this situation we are not talking about engine oil pressure so do not compare it to this issue . This specific pressure your reading is NOT suppose to be in the cooler line and in your front pump forcing the converter forward . The more you operate this above the pressure it's at now , it will ruin the bearing quickly . Do the bypass test , see what you have .

[sansabarJ]

Oh ok , so you did the bypass and it's 30 . Your coolers are adding in 20 psi . I'm not happy with that . I use the HAYDEN plate and fin cooler . It the black premium cooler that are an OEM
cooler design . Yes that 20 psi is not good . Sounds like your radiator cooler is restricted .You can run the air cooler and no radiator cooler. I have used the large black plate and fin on many trucks with no radiator cooler used and never any temperature issue . Use a decent size cooler though .
Read the GVW rating on coolers . My rule is the larger is best . Your off-road and slow going you want optimum cooling . Oreilly auto parts , car quest AutoZone that offered the HAYDEN will be just fine. Plate and fin , not those cheap tube coolers , ALTHOUGH ... they do work too , just the other style does a better job .

[mjdriver]

Oh ok , so you did the bypass and it's 30 . Your coolers are adding in 20 psi . I'm not happy with that . I use the HAYDEN plate and fin cooler . It the black premium cooler that are an OEM
cooler design . Yes that 20 psi is not good . Sounds like your radiator cooler is restricted .You can run the air cooler and no radiator cooler. I have used the large black plate and fin on many trucks with no radiator cooler used and never any temperature issue . Use a decent size cooler though .
Read the GVW rating on coolers . My rule is the larger is best . Your off-road and slow going you want optimum cooling . Oreilly auto parts , car quest AutoZone that offered the HAYDEN will be just fine. Plate and fin , not those cheap tube coolers , ALTHOUGH ... they do work too , just the other style does a better job .

Thanks for the info, what fluid do you recommend for the th400?

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[sansabarJ]

Just use dextron 3 or equivalent. Most ATF fluids are dextron Mercon or a universal ATF . Dextron is GM so look for dextron to be on the label. Don't get any trick synthetic or other type .

[mjdriver]

Do you guys think a bound trans output shaft could couse this issue? I remember I had to pretty much force the transfer case onto the trans when assembled them, I replaced the sun gear in the reduction unit with a used one, the splines did not want to play nicely together. Just want to cover all bases.

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[Stuka]

It’s been a while since I have seen the inside of a TH400, but if you had to push the t-case on like you describe, is it possible the output shaft got forced in farther than it should be? Not even sure that could cause high line pressures, but it’s a thought.

[fulsizjeep]

Since you changed out the sun gear, there must have been some damage to the 10 spline union for the tranny tail shaft. Usually, the tranny tail shaft also gets a beating when the 10 spline is banged up in sun gear. Did you inspect the tail shaft splines? They could be worn to a point where sliding a good used sun gear onto the tranny tail shaft is not mating well and meets resistance.

[mjdriver]

Since you changed out the sun gear, there must have been some damage to the 10 spline union for the tranny tail shaft. Usually, the tranny tail shaft also gets a beating when the 10 spline is banged up in sun gear. Did you inspect the tail shaft splines? They could be worn to a point where sliding a good used sun gear onto the tranny tail shaft is not mating well and meets resistance.

Ok guys here's the whole story, truck did not come with the reduction unit, I purchased a reduction unit off eBay, found the splines on the sun gear at least 50% worn, so again to eBay to take my chances on a used sun gear, got it and swapped it into my reduction unit. Both the splines on the trans output shaft an sun gear appeared to be in good shape. However when I went to slide the reduction on it wouldn't slide on the shaft easily, I had to tap on the reduction unit with a mallet and piece of wood to drive it on. I tried greasing the splines and even filing some burs but it didn't seem to make a difference so I just sent it.

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[fulsizjeep]

OH, thanks for sharing more detail. You should not ever have to use a mallet to push those together. So that "tight" issue could be the 10 spline union or it could be something with the pinion cage mating to ring gear and sun gear. I had to replace the pinion cage once because the pinion gears were loose on the pins and made a terrible fit with ring gear and sun gear. OR it could even be something in the mating surface between the main case and low range case. It's not likely that this issue is related to your thrust bearing failure.

[mjdriver]

OH, thanks for sharing more detail. You should not ever have to use a mallet to push those together. So that "tight" issue could be the 10 spline union or it could be something with the pinion cage mating to ring gear and sun gear. I had to replace the pinion cage once because the pinion gears were loose on the pins and made a terrible fit with ring gear and sun gear. OR it could even be something in the mating surface between the main case and low range case. It's not likely that this issue is related to your thrust bearing failure.

Lol didn't think it was normal , I haven't had any issues with the t case yet. And ya I doubt its related to my issue. Thanks for the imput

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[sansabarJ]

Is there any chance one of the members here will give you a convertor to try if they have one . I know most everyone looks to be doing GRAND Wag LS swaps though .IE: 727trans .
Be great if you could just swap out that convertor . I'm sure you don't wish to have to do that but seems your only option here . Never beat on the rear shaft or force anything , good chance of damaging the case or internal parts . As has been mention , mismatch on the splines . May be hard now to get the Tcase off .


SansabarJ