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Old 01-16-2019, 03:18 PM
snik snik is offline
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Quote:
Originally Posted by RRPhil View Post
I see 5HP24s at that mileage quite frequently and they’re in excellent condition (but others are completely ‘worn out’ at much lower mileages). When I check the thickness of the friction plates at 200k miles they’re often identical to brand new plates because the control system is so sensitive to any unplanned clutch slip that it immediately flags failsafe if there’s anything going on that could generate wear and damage. The long-term adaptions stored in the controller tweak the clutch control pressures over the years to maintain the shift times, again, protecting the clutches. Arguably at such a high mileage you should swap the controller with the transmission to preserve these settings.



Clearly, it’s a bit of a lottery fitting something at that mileage without knowing its duty-cycle history. If it’s been driven gently for the whole of its life the transmission could last indefinitely. If it’s been used for towing, frequent hill climbing, driven aggressively, etc. it may be much further through its fatigue life. Similarly, you have no way of knowing if the fluid has overheated in the past and therefore oxidised and massively reduced its protection/life.



Common failures at high mileages are the A-clutch drum snap ring groove (for transmissions built before November 2000), the B-clutch hub/C-clutch drum axial bearing failure, the F-brake piston seal (for transmissions built before August 2001) and wear in the torque converter lock-up clutch. Other than these well-known weaknesses the rest of the transmission is very durable. If the transmission has previously been rebuilt then the above issues may already have been addressed? Transmissions built after October 2001 have all the latest development fixes from the factory. If you want to know the date of manufacture of a particular transmission just let me have the serial number off the green plate riveted to the side of the casing.



Phil


That makes the 5HP sound awesome.
What's the main differences in failures and wear parts you've seen with the 6HP? Do they share any strengths or weaknesses with the 5HP, or is the 6HP totally different?


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