I have to change the fluid about every 12k because of the heat burning the fluid. I hardly ever see any brass in the fluid just this black junk. It is like a scum and it is on the bottom of the pan and has to be washed out with solvent.

Occasionally I will get a harsh shift from 2nd to 3rd, otherwise the tranny works fine.

 

> fluid just this black junk

Most likely the friction material from the clutches.

Just jumping in on this thread, I agree, check the converter. A bad converter (or bad spec one) will raise your temps a lot as it slips.

They might have used the original one instead of replacing it.

 

I have to agree with the part about clutch material being the black gook in the pan. No doubt this tranny is in the process of self destruct and unless someone intervenes real soon it will die a slow hard death. Burnt fluid and gook in the pan?... This baby is about to go FUBAR and maybe for all the wrong reasons... not the tranny itself.

Your mention of converter slip makes sense... a definite 'isolated' point for heat generation without evidence of metalic material in the pan. Definitely a source of heat generation beyond the cooling capicity of normal fluid flow in spite of external coolers. Just suppose the slippage is thermal related and as it heats it slips more...and more. And, then add a load and the event takes place even faster.

Would be interesting to know the 'rate of rise' in the fluid temp. as it relates to load (no trailer) or loaded.

Oh...as a side note... at these repeated and somewhat sustained 300 degree or so temps then pretty soon we are gonna see some well baked or fried rubber materials including seals starting to go and then replacing the tranny fluid should be no problem because it won't require manual draining.

 

To answer your load/no load question, the tranny actually runs cold now with all of the additional cooling will running solo. It runs relative cool while towing on level ground (around 200) but the minute I start pulling any grade the temp rises. With a 2 or 3 percent grade the temp will run up to about 240. If the grade goes up to 5 or 6 percent or is sustained for several miles like the Baker Grade, Cajon pass, Grapevine, etc. the temp will run up to 300 degrees. It gets so hot that you can smell it burning. It starts cooling down almost as rapidly as it heats up as soon as you start going back downhill.

 

Have the converor replaced before the transmission is ready for PB&J.

 

I replaced the front cooler, shown as cooler 5, with an old A/C condenser shown a cooler 3 & 4. I re-inspected all of the cooler lines and found no kinks, flat spots, or sharp bends. I did find the return line touching the new head pipe at one spot and I relocated the line away from it. I took the line loose right where it goes into the tranny and put it into a clear graduated one gallon jug. I started up the truck and watched the flow. It pumped two quarts into the jug in less than thirty five seconds. This was at idle, (650rpm) the manual calls for one quart in 20 seconds at 1000 rpm so I assume there is no flow problems. The flow was the same with the original cooler as well as the A/C condenser.

Saturday was a warm day (about 98 degrees) so I thought it would be a good day to check out the new cooler. I hooked the fifth wheel up and pulled it up Johnson pass. At the bottom of the grade the temp was only about 210 so, I was feeling pretty good, but when I started pulling the grade the temps went up. The tranny was at 250 degrees by the time I crested the ridge. That’s only about 10 to 15 degrees difference from the old tranny cooler. I did notice that burning smell was not there this time, but this thing is still running too hot. I can’t believe the converter is slipping because of the way it pulls and the way the truck backs down on compression. When I let off of the gas, the truck really starts slowing down just from the engine compression. Would it do this if the converter was slipping?

At this point, I don’t know what to do. I guess the best bet would be to change the rear end first and see what difference it makes. But I still go back to the original fact that the darn thing never ran this hot until I had the tranny rebuilt.

I guess I made up my mind, I just ordered a TCI-443630 converter from Summit this morning. I will re-post as soon as I put it in and test it out.