ZF Model 80lv low pressure

[Europeanautoctr]

I have a 2005 Searay 39 sundancer with ZF 80LV transmissions with cummins 370 qsb engines. On cold start up both temps 60 degrees, pressures both 350 – 375, I have a 15 minute ride out of channel pressure same temp 90 degrees.
on first sea trial noticed starboard transmission temp raising to 160 degrees after crusing for 20 minutes & port side 110 degrees. Engine temp on both engines 177 degrees. When at clutch speed pressure drops to 195 PSI on starboard side & 285 on port side readings from smart craft gauges. After moving at clutch speed(5knots), will cool down & pressure goes up to 285. 2 years ago a after cooler pencil zinc broke off & blocked inlet to transmission cooler, same temp & pressure problem then, removed broken zinc & sea trailed-OK. replaced turbo aftercooler asembly’s on both engines 2 weeks ago. Both transmission coolers last year. I removed all raw water cooling hoses from pump to exhaust & checked for any restrictions(none found). Checked & replaced transmission filter, checked lower seal in transmission case at bottom of filter . 2 years ago starboard side transmission piston rings cracked on input shaft(replaced all 3 rings & front pump ) this year i pulled off front pump & checked pision rings(ok), replaced all 3 rings again. Any suggestions???????? I was thinking of pulling boat to check pick up screen to seacock, boat yard painted boat bottom, possible restrictions at screen??? but engine temp not affected. Again any suggestions????

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[Europeanautoctr]

low pressure.

PS no dragging on the sahft

[Europeanautoctr]

low pressure.

Up date. I had the boat hauled, cleaned through hull pick up screen ( slightly pated closed) I removed the water pick up hose from sea cock to raw water pump, checked for any blockage(none). I ran a hose from sea cock to raw water pump to eleminate sea strainer, i swapped transmission oil coolers, i swapped the front pump with hoses, checked the new rings, sea trailed same problem. I have had alot opf electrolysis problems on that starboard side, going throgh diesel fuel coolers every two years. the only raw water cooling hose that was not changed is the hose from transmission cooler exit to engine cooler. maybe time to call ZF before i condem the transmission. Any possible failure in the new turbo after cooler, it only has 3 hours of run time.I did remove the upper cap & checked water flow through the core. The transmission cooler is next in line in the raw water flow. . HELP!!!!!!!!!!!!!!!!!!

[Europeanautoctr]

low pressure.

I already replaced rings, fluid is not dark i will swap pump this weekend & follow up next week. Enjoy the weekend

[Tony Athens]

Not an “easy to guide” post—–The ZF80IV has a very colorfull history…………………. Any dragging on the suspect gear in neutral? Oil slightly dark?

1st thing I’d do is put in 15-40W Engine oil……………. See is anything changes..

Since you seem to be a “hands-on” guy– swap oil pump assemblies and see if the issue follow the pump–While off, look very close at the rings —

Tony

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