Charles Navarro

Exactly. The reason we see less failures with Tiptronics are that there are less of them. It's a fact that as surface speeds increase, wear and lubrication requirements for ball bearings and roller bearings decrease.

The reason they went with the larger 6305 series bearing in the 06-08 cars is that that increases surface speed as well as load capacity, restoring load rating to that of the original dual row bearing.

AdamIsAdam

Can you explain this to us non-engineers? Is it because at higher speeds the parts start to float a bit? Maybe centrifugal force kicks in? Just curious.

Charles Navarro

The bearing operates in boundary and mixed lubrication regime, meaning the ball or roller has contact with the race and also where it's riding on the oil film. For a given load, the faster the bearing turns, the less oil film is required to maintain boundary lubrication.

Does that help?

AdamIsAdam

No! It just makes me wish I paid more attention in high school. ;-) lol

Seriously, I do believe I understand the general idea.

On a related note, the Shelby GT350 Voodoo engines are experiencing some premature, unexplained (and unidentified) engine failures. I'm reading all the forums (because I have a new one myself) and freaking myself out. I thought to myself, now I have TWO cars that could suddenly and without warning explode into a million, expensive pieces! On the Shelby forums there are more than a few 911 owners. I've been trying to draw analogies between the two cars. I figure, one day when we have much more info to analyze (ie, failed engines that are out of warranty (right now Ford just confiscates the entire bad engine from the dealer and sends a new one rather than allow anyone to open it up!)) someone will have more knowledge like your team does about the IMS issue.

It seems most of the engine failures are related to a lack of/reduced amount of oil. These engines mysteriously develop an appetite for consuming oil. People report that they never burned a drop of oil, then they hear a noise and mysteriously, the dipstick shows no oil! It takes 5 quarts (holds 10) then later find engine damage. But some of these engines ARE actually consuming oil at very high rates even when they are checked regularly. Ford checks consumption and replaces as warranted (and warrantied). So my theory is that somehow, some of these engines are getting low on oil one way or another, and then there are issues. I check mine before every drive (it's not my DD).

Getting back to you and Jake, I've been trying to follow the your recommendations in terms of how to drive and maintain these engines. Basically, don't drive it if you can't get it fully up to temp (no short trips). Don't beat on it cold. And CHANGE THE OIL every 5k or 6 months regardless. Maybe that will keep them from developing a thirst for oil in the first place. And if it does take a qt every 1 or 2k miles, fine. Just don't let it get 5 quarts low! (I will say that there are folks who report that they really were on top of things and still, the engine suddenly started consuming oil or suddenly something failed. But since Ford just takes back those bad engines whole, we don't know what's going wrong.) (Oh, some theorize that since the engines are individually signed by the two man team that hand builds each one, they don't want anyone else opening them up to protect their reputations/jobs.)

If you're bored, here's the 63 page thread on engine failures (on one forum): https://www.mustang6g.com/forums/thr...thread.104010/

Sorry for the digression, but I wanted to share the similarities, especially since the GT350 seems to attract so many 911 owners.

Charles Navarro

I'm actually working on a directive for checking oil level now. Across the board, engines are getting thirsty. GM's latest bulletin states 1 quart per 2000 miles is normal and expected and 1 quart in 500 miles on performance models. Manufacturers have gone to 2-3# oil controls and surface finishes we consider a mirror finish on bores for friction reduction for fuel economy, however with thinner oils and fuel dilution, it's no surprise we end up with problems.

808Bill

What should I do?
My new to me 996 with factory replaced engine and BIG IMSB is my DD. Short 12min commute gets up to temp and then I'm there. Same on my trip home but it's up hill and curvy so I'll stretch it out every chance I get.

AdamIsAdam

I'd love to hear about your directives on that.

Ford Performance engineers said up to a quart every 800 miles while on the track, or more, is normal. I seem to recall my 996 manual also making claims like that related to track driving. It's the street high consumption that's nuts. Interesting comments about friction reduction in the cylinders. Thanks.

AussieRick

First post so be kind:
2000 996 C4 Tip Cab. Don’t really know provenance or service history past last owner. Now has 204,000 km on the clock, I drive it “with spirit” and it runs like a dream.
I saw a post earlier where someone stated engine numbers to IMS bearing fitted (Single/Dual) Went out to get engine number and lost post.
Can someone point me to that post?
Great site guys.
Thanks.

dan_189

Welcome Rick! Make sure you get onto the PFA as well for some local get togethers

Being a 2000 with near certainty yours will have a dual row IMSB. Check out the PCNA videos with Jake for a really good run down on the IMSB.

Charles Navarro

Change your oil much more frequently - at most every 3k miles or every 3 months. You really need to pencil in there some days where you can drive it an extended period of at least 30 minutes, if not longer, if the weather is cold outside, as it will take significantly longer for the oil to get to get to temp. Ideally we want to see oil temp once in a while above 220F to get moisture buildup out of the crankcase. That's why when that can't happen, shorter intervals are needed for oi changes.

808Bill

Got it...Cold here is the low 60's for only a few hours fortunately.

escimo

Cool, I got to be the "996th" vote in the poll for No IMS issues..

1999 996 C2 78,000 Miles
Recently I pulled the engine and trans to replace the clutch, AOS, etc. Pulled the factory original dual row bearing and it appeared to be in perfect condition with no noticeable play or damage.
Will probably replace it anyway with the LN or RND roller bearing. Love this car..
Happy Hollidays

808Bill

You have to replace it as you can't pull a bearing and reuse it.

neadaporsh

2000 996, 95,500 miles no IMS failure or replacement........frequent oil changes

996AE

Oil changes every 90 days.

Wow.