07-17-2007, 09:23 AM #1
How common is thrust bearing failure?
I have gutted 5 4-tec cases in 3 weeks and ALL had failed thrust bearings or blackened thust surface on the crank and were going to fail I am starting to believe that combinations of the impeller shaft hyd. fwd. and the engine moving to the rear flexing on its mounts during acceleration and WOT...If so, I have a fix for this in my demented head Just want some feedback from people who have been inside these things and what they have seen. I tossed a rod totaling my block at 33 hrs., the crank looked perfect aside from the thrust bearing cooked and about to fail even though it had nothing to do w/ my rod issue (that was me ).I see 2 design issues here. Go out to the shop and check those cases and cranks, and tell me what u see.............
07-17-2007, 09:26 AM #2
I`m sure the thrust bearing takes alot of abuse for unhook/hook (load and unload) as well as on/off throttle. I don`t see a problem at all with design though. At least `05 and `06 models. Tony rides in the rough even out to ship island and has 150hrs on his mill. No probs at all even with a failed oil pump.
07-17-2007, 09:33 AM #3
the problem I am seeing is the crank grabbing the bearing (only a half-circle) and spin it on the thrust surface wiping out the case...it will do this and not damage the main bearing...it should be made like automotive engine thrust bearings...as in standard 2-piece, not 3
07-17-2007, 09:35 AM #4
in additon, or instead of the above (perhaps more effective) would be to have a roller thrust bearing external between pto and the shaft, preventing forward movement..
07-17-2007, 09:48 AM #5
I have heard of no less than 15 thrust bearing failures since i have been into these 4-tec's (since 2004)
All the more reason to run a solid front engine mount to keep that engine from moving rearward against the driveshaft in choppy conditions.
07-17-2007, 10:09 AM #6
greetings from vegas Jerry!!!
07-17-2007, 11:43 AM #7
Yup, just found out last week that my crank's walkin' back and forth. Engine's been pulled, waiting to get it disassembled. Don't know the internal damage assessment yet.
Red Devil and I were talking about this last week and wondered if there's a large number of GTX SC with this problem. Any other couch drivers have this happen to them?
Any solution, demented or not, is welcome.
Last edited by gtxsc03; 07-17-2007 at 12:02 PM.
07-17-2007, 12:00 PM #8
out of town now, but will be talking w/ someone about a "case-saver" all-in-1 thrust-crank bearing. I have 2 cases I can save this way w/minor machining. The main-bearing crank journal diameter will determine the extent of the machining to use a bearing part# that already exists......unless we have someone from clevite on the forum? They could spec the bearing based on the crank, but then that would take the hassle out of it wouldn't it?
07-17-2007, 12:09 PM #9
The prop (impeller) is supported by the jet pump bearings, so I think Jerry is right: the load on the thrust bearing is due to the motor flexing backwards on its mounts.
07-17-2007, 12:39 PM #10
Yep, you would be surprised how much movement is in the stock front mount. If you ever pull your engine just grab that front mount and you will see you can flex it back and forth quite a bit. The solid front mount is the way to go!
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