An update on this -- the transmission went out once again. Since the repairs last month, all shifts have felt right and looked beautiful on the tachomoeter. Back to like new mileage of 21 mpg. Just before it went out today, I did a 30 mile stretch on the interstate going 70 mph and getting 2000 rpm's the entire time, no variation or surprise shifts -- performed beautifully. Then I simply lost fourth gear. I limped the remaining 100 miles.

Could it be that the rear differential is dragging on the transmission and making it work harder? The only service the rear diff has had is the cover. The only hint of a problem back there is maybe a low growl on decel.

 

Well now that you got the lock up issue solved hopefully that will help the next transmission. I would also look into the radiator for cross contamination of trans fluid and antifreeze. Maybe the temp is just getting hot. Are these rebuilt transmissions or junkyard swaps. A trans shop would most likely check and flush the cooler to ensure it didn't return for warranty work. If these are junk yard swaps they are most likely on their last legs anyway and the engine problems didn't help them. If you just lost only 4th I would think that would have to be a hard part failure. 3rd and 4th use the same clutch pack, so if that burnt up 2nd would be your highest gear. If the sunshell broke or striped I believe you lose reverse, second and fourth. You should get a rebuilt trans with a rebuilt torque converter and have your cooler checked and flushed. You could also roll the dice with a junkyard swap, but it sounds like you have lost a bit already. I would go with warranty.

 

Yes, I lost reverse, second, and fourth. My transmission guy had repaired the damaged hard parts on the junkyard transmission from the latest in the series of warranty replacements from the certain company these came from. He had also checked and flushed the cooler. What he wasn't happy with was the choice of some of the parts the company used in shoring up the junkyard model.

He is going to make good on the labor and get a core that he can rebuild himself. If there is cross-contamination of trans fluid and coolant, what is causing that? The overheat idea makes sense. You don't think the rear diff could be causing these sorts of transmission failures?

- Thanks -

 

The contamination can come from where trans cooler lines run into radiator. The "beast" sun shell is the way to go for replacement part fixing no reverse second and fourth. Just changing that to get a junk trans going again is cutting a lot of corners. The tcc valve should be redone. That max line pressure slam or hard shift from 1 to 2 will kill hard parts. Pump valve is also a must upgrade. Pump was rebuilt I hope. Sounds like you could be getting a lesson in "you get what you pay for" lol.

 

My mechanic did not detect any cross contamination. The next warranty transmission is installed. I'm still wary, and still looking to see if there is something from my vehicle that could be causing the repeated transmission failures.

Using it just for short trips, and going no more than 55 mph, I am seeing perfect RPM's for each shift, and good gas mileage, just like I was getting before the last failure. With many things replaced or crossed off the list of culprits, I wonder if the PCM is something that could be causing problems? Or could perhaps there be a problem in the way the new engine was put in relative to the transmission?

 

Did any one check for cooler flow while driving? Sonnax makes a cooler flow tester. maybe install an aftermarket trans-cooler & bypass the radiator cooler. Has anyone ever tested for TCC slip while driving? Cooler flow is reduced during 4th gear. that's why TCC is so important at highway speeds. Less heat build up with TCC. No TCC while in 4th forces torque multiplication in the converter (.70-1 gear ratio). I worked at a Rebuild Center that used 150PSI shop air to flush coolers. We had several trans failures that looked heat related, but were told the coolers tested good. Come to find out when we checked the radiators they wouldn't flow fluid at 30 PSI. We stole the Flow meter off of the transmission dyno to find it. Just some thoughts after reading the thread.

 

No one has tested for cooler flow while driving. That sounds like an interesting possibility. No one has tested the TCC for slip while driving. I don't see any changes on the tach while driving at steady speeds, and I don't feel anything.

With those radiators that weren't flowing fluid past 30 PSI, is that due to the style of radiator? I had a new one put in with the engine. All of the trans faliures have occurred in the year and half since that was put in.