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Discussion Starter #1
No.9 thrust mod requires drilling cooler return to 3/16 and adding an 1/8 hole for thrust washer (there's a 5/64 hole for sprag lube) then there's two polygonal grooves in the bushing for fluid release plus bushing clearance for cooling/friction reduction and last there's a lube hole in the shaft that measures .180+-. Is the output shaft fed from the cooler return at the rear case bushing or is it pressurized from else where? If it is fed from cooler return should I stop drilling at 1/8in thrust hole and not go all the way to case bushing so I maintain pressure at thrust? This will be a high load endurance tranny ran in 1st & 2nd for hours.
 

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Actually, my opinion is the opposite. As the bushing and shaft are self-regulating to a degree, I drill 3/16" all the way to the bushing. I only drill for #9 thrust to 3/32" like I show here. 3/32" at return pressure is a LOT of flow. My angle is this will help keep bushing and shaft flow up while lubricating #9 as much as it can reasonably use. If #9 really needs more, then I feel it's time for a roller bearing in the #9 position. If you have any doubt for an endurance application, I would say to rollerize it.

David
 

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Discussion Starter #3
Thanks PSIG I was starting to think I wouldn't get a reply. I did what you show but drilled 1/8 in instead of 3/32, I may have missed it but don't recall seen a bit size on this site so I found it here Classic Broncos .com - Tech: Tips on improving the internals of a C4 automatic transmission. I agree with you about the self regulation of the bushing and then I saw the lube hole in the shaft and that got me concerned. I think return fluid will lube the sprag, no.9 thrust, rear case bushing, then flows forward in output shaft to lube planetaries then splashes back to pan. If this is correct good bushings should regulate fine. Am I correct on this? And your right roller is the way to go but that is next summer.
 

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Yes that is correct . I only drill that extra lube to the #9 washer @ 1/16". The factory C5 used a 9/64 hole for the #9. Open the case passage to 3/16, I never drill through the rear bush.

Good bushes will help regulate i believe . The factory sun gear in a C5 also has 4 large feed holes @ .094" to each gearsets where the C4 only has 3 or 4 @ .040"
I drill only one feed hole in the sungear to the front planets @ .100" .

All this bleeds off lube oil. But keep in mind that removing the checkballs in the stator support should increase lube flow to account for the mods
 

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+1 to all that. In-fact, at 3/32 I've barely seen contact marks and no wear at 500+ hp, so I'll probably drop to 1/16 on my thrusts like Greg. Based on the experience of many others, it seems the line is about 600hp where the force pushes through the lube film and #9 gets contact, and any more lube doesn't really help. The fluid used makes a large difference I'm sure, as some have pushed towards 800hp with no #9 issues, while others spin them at 500. Sharp or low rpm loading (like nitrous) and assembly end-clearance is probably a factor for some as well. I have more concern at that level with the planetary set than #9.

@ Greg - speaking of that, while planet rollers are nice, they are a real pain compared to the rest. What level do you feel the "scoop slot" lube mods are good to before requiring rollers or more planets? Any general opinion on that?

David
 

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Discussion Starter #6
What you are saying makes sense in that as long as the no.9 is getting something it will live till power and heat over ride the fluid film barrier of the type of fluid being used then one must switch to roller. I am curious as to why the return feed would not be the same size as the pump feed, any one have info on that? Also the one and two selectives, my books give no info on this, when you change one do you change the other always keeping them the same as in both FM1-FM2-FM3-ect. and just assume they both require the same thickness selective. I know this is a noobie question but this is the only C4 in my Ford collection.
 

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I find now most of the front planets are worn so need something done with them . Usually anything looking to make any power i'd be considering either the 6 gear planets of rollers on the 3 gears .
I've not run the roller 3 gears as yet but from what i been reading some guys are having great success with them. I have just had 6 housings machined to do the rollers under each gear so will use them in the future .

I've used to local 4 gear planets made here but for the $$$ they cost i'm not convinced they are all that much better than a modified 3 gears. One 4 gearset i used still showed some wear on the thrust washers . They have the lube grooves under each washer also.

As for the lube grooves in the factory cases i've seen a figure of 500 FWHP as a limit that i'd think a reasonable figure for the grooves alone under each gear . One set i did ran 540 RWHP for some time with no issues but the car was sold on after so not sure how long they lasted .

As for the #1 + #2 washers to set the endfloat there is absolutely no relationship between sizes . I did an article a while ago is on here how to set up endfloat correctly in the tech archives .

You must set the trans up first using the small #2 washer on the stator support to get you endfloat correct.
Then on the bench after you set up the clutch drums on the pump using the correct #2 you selected then figure out the correct #1 washer that is a snug fit between the clutch drum and the pump housing.

So to answer the question when to go bearings in the planets or extra gears i'd say 500 FWHP and over as a good figure .

As for the rule of thumb i use for the # washer, if the trans is a mild one and is using washers it gets the lube mod @ #9, if it rollers elsewhere it gets a roller #9.
When using a roller #9 i don't drill any extra lube holes in the back of the case , what's there originally to lube the washer and roller clutch is sufficient for the new roller bearing
 

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Discussion Starter #8
Thanks Greg & Psig this helps a lot, my book shows end play setup with the same procedure as the C6 and I didn't think that was right. I'll be starting with a 355ci smooth to mild idle cam on pump gas with an SK-4 TransGo kit with stock type converter, the bad thing is I grabbed a dental pick and put a nice scratch across the input shaft face, so much for all Bronco's having hardened input shafts. I'm going to do a stock rebuild with kevlar bands, pump, case, and drum oil mods setting clearances to minimum then recheck at the 1000 miles of abuse mark to see where problem areas are. Money wise before I buy hardened and roller parts I'll switch to one of my C6/NP205's laying around as weight and ET's are not critical for me. Thanks again guys you've been a great help!
 
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