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Discussion Starter · #1 ·
So I have a question for you all. I just installed my SYE yesterday in my np231 transfercase. I replaced a lot of parts while I had the t-case out of the Jeep. I replaced a broken shift mode fork, new pads on the range fork, new chain, new front/rear/input seals and new seal on the transmission output as well. Put 2 quarts of fresh ATF4 in there as well once completed.

Since I did the install I drove over to the local driveshaft shop to have a new cv rear driveshaft made for my Jeep. The mechanic there crawled under the jeep to take measurements and noticed some extreme heat coming from the transfercase. He grabbed the yoke to try to turn it and let go immediately. He said it shouldnt be that hot and something seemed wrong. He wasn't 100% sure but to his knowledge he thought he should be able to grab the yoke but couldnt.

He was thinking the oil pump wasn't hooked up properly or it fill off when we put the t-case back together. Could this be possible? I never really checked the temps or felt the t-case when it was stock (i've only had the jeep for 1.5 months) so i dont know how it was before the SYE install. Could it get extra hot because the driveshaft is not connected to it so it's freely moving vs having to move 2 wheels?

I have a laser temp checker and I checked the t-case temps when I got home and they were about 140-150 on the rear case half and then on the new yoke/case from the SYE we installed the temps were anywhere from 150-170 and the yoke itself was about 130. This was after driving down the freeway for about 15 miles.

I really dont feel like splitting the t-case open again just to see if the oil pump line is properly hooked up if I dont have to. Could you please chime in with your temps and if this is normal? I also dont want the t-case to grenade on me this weekend when I go wheeling. I will have my new cv rear driveshaft today. Should I install that and then go for a drive and check temps to see if they have cooled down? I live in Arizona and the current ambient temp today is about 65 outside.

Thanks and any feedback is appreciated as to what to do.
 

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Discussion Starter · #2 ·
**I forgot to add that I was driving around in 4WD HIGH on the freeway at 65mph for about 13 miles to get to the driveshaft shop. Its the only way I could get there since I dont have a rear driveshaft installed right now. So this would probably add a lot of extra heat to the transfercase right? Plus the t-case is right next to the exhaust and CAT which puts out 300+ temps.
 

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I would just drive it. New parts will always generate some extra heat. I'm sure 4wd helped jack the temperature up too. If something is wrong in there, it will eventually break.
 

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I suspect 4hi at 65mph would generate some heat. Put the rear driveshaft on, drive it in 2hi and see if the temp is less. Then tool around a bit in 4hi at regular 4x4 speeds on loose dirt and see if the temp is less. I'd lean more toward heat generated from 4hi freeway driving versus some other mystery problem.
 

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Discussion Starter · #5 ·
Hmm i'm going to try to find a buddy so we can check his temps in his Jeep. I have a big weekend of wheeling coming up and I would have to grenade my newly rebuilt np231 out in the middle of nowhere because it wasn't getting oil pumped into it.

Does any of you have an infared temp gun so you could check the temp of your transfercase after a good drive? I'm curious what your temps are at.
 

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If you can put your hand in the TC for some seconds without burning your fingers the temperature should be ok.

If the housing feels ok at the bottom and only the small housing at the yoke is too hot there could be a problem with the oil pump.
 

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Discussion Starter · #8 ·
ya the hose looked perfectly fine. I pulled it out, cleaned it off because it was full of crud and lots of other junk as it probably hadn't been cleaned in years. I made it look brand new and reinserted it and made sure it was plugged into that little plate in the rear housing before we put the case halves together.

So what are your thoughts on driving it in 4WH on the freeway for 13 miles at 65mph without a rear driveshaft connected? Would it spin faster then normal since it doesn't have any resistance? Normally it's turning a drive shaft and powering the rear axle to move the 2 rear tires. If it has nothing connected to it would it spin faster and cause it to get hot?
 

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Discussion Starter · #9 ·
If you can put your hand in the TC for some seconds without burning your fingers the temperature should be ok.

If the housing feels ok at the bottom and only the small housing at the yoke is too hot there could be a problem with the oil pump.
I used an infrared temp gauge with a laser on it and checked the temps. The rear t-case case half was like 140-150 degrees, the rear housing from the new SYE kit was like 150-170 and the rear yoke itself was 130 degrees. These temps were recorded immediately after I got done driving on the freeway in 4WH for 13 miles.
 

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170 F is still ok.

I drive +500 mls in 4H before my new CV driveshaft arrived. The TC was a bit warmer then in 2H but that was ok.

I would worry about temperatures of over 210-220 F...
 

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Come back to life! I'm having the same issue with my new sye on my yj. The sye rear housing/yoke will be very hot to touch after a longer drive. Did you ever find a solution, did anything break? Cheers.
 

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Did you ever feel your t case before you installed it? I put the SYE on mine and thought the same thing but after doing some checking I think it's fine an automatic transmission runs anywhere between 180 -210 and it has planetary gears in it so the atf can handle the heat i just drove my dodge 2500 70 mph for 30 miles and checked the temp on the t case it is comparable to the temp on the 231 with the SYE I know my dodge has the 241 but its still almost the same tcase and it doesnt have the SYE hope that helps
 

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Never did feel it before the SYE. So I really don't have a baseline temperature. After only a 10 minute drive for the yoke to be too hot to touch seems wrong.. I'm 99% sure the oil flinger tube was properly inserted. Could it be the bearing is bad and generating heat?
 

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could be but I wouldn't think a brand new bearing would already be bad what brand SYE did you put in it I'll drive mine 10 -15 tonight and tell you how hot the yoke is with a temp gun I'll also temp gun my 241 non SYE case so you have two numbers to compare to
 

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ok I drove the jeep today for 10-15 miles then used the temp gun on it it was 170 on the tailhousing and yoke and 160 on the case also drove my non SYE 241 in my dodge and it was the exact same there are some temps for you I've been driving both for a while with no faults I would use a temp gun and see just how hot its really getting
 
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