I’ll be changing the diff and MT oil at 50k.

 

If you lower the car, the default distance from the diff axle to the wheel hub will change and make a non-designed stress to the system. Properly lowered cars should have the diff lowered also (you can google "diff drop" for more info). Usually very small drops are OK, but around an inch you can see problems. Not to mention other aligment issues associated with lowering the car, but it seems most people don't care at all.

 

Wouldn’t the resolution be to raise the diff up into the body rather than to lower it? Doing that would negate the advantage of increased negative camber at the rear tires.

I’ve lowered every single street and track car I’ve ever owned and have never had a diff. failure. I would think the CV or universal joints would absorb the offset forces from the minor misalignment which is constantly present during suspension travel.

 

100% correct. In fact, in a simple form, think about any car and how much the suspension moves up and down constantly. There are lots of tolerances in drivetrain and suspension components. At any rate...Similar to you, I have lowered and modified the last 10-15 BMWs and Porsches I have had, and never had any failures, and have raced many of them...no issues or failures. Hopefully did not just Jinx myself

DC

 

Agreed with Unhingd and Rock. Maybe he was thinking along the lines of when they lift trucks, but that is a significant change. In those applications, they use tapered shims to adjust the angle of the pinion gear and set the backlash appropriately. They don't lower the diff (or raise), they rotate it. I can't imagine lowering a car an inch is going to affect the pinion angle to a degree where the universal joints aren't compensating enough.

 

True, but a large number of owners are seeing heavy contamination (we assume from the friction plates) in the oil after 25K.

 

I for one am not sold on lowering cars. I have a very good friend that had a bad experience when he had his Z06 Corvette lowered. He is a very experienced car guy I have
known him since the late 60's, met him walking down the street past his house saw him cleaning and waxing his Plymouth muscle car.

He told me he lowering it, took a great handling car and made it just a good handling car. He was honest with me and said he f....up and drank the coolaid.

My thoughts on major mods to any car is most cases the engineers that design and do the extensive analysis on the sub systems of these cars get them as close to
optimal as possible for most driving conditions.
​​​​​
There is a lot of snake oil sales people out there pedaling these aftermarket products.

Just to be clear I am not saying anyone is wrong for lowering their car.

On the diff failure issue My car is going in for a diff fluid change on the 7th it has 40k miles. Funny thing is when I called to setup the appointment the service rep said there is no
schedule for doing this in there paper work for the f type and asked why I was requesting it? They are charging my $180 for doing the fluid change. I thought this was reasonable.
Everyone have a happy and safe 4th of July.

 

Considering some of the quality control issues I have read about on these forums, I wonder if the majority of the failures are from incorrect fluid levels from the factory?
Overfill = leaking seal
Under-fill = premature failure

Either way, piece of mind would be achieved by early fluid replacement.
I plan to do this soon and am only at 12k but my warranty just expired this month.

 

Engineers design cars to specs and marketing department tells them what will sell to the masses. Also reliability....they keep them as safe as they can to make it through warranty....Not for max performance( few exclusions like 911 GT2 RS GT3 etc..).

So the cars are engineered to sell and make profit, not optimal performance / looks....and they make them at a ride height that will clear in most driving situations so they do not have to hear about that from customers too.

It is a personal choice to lower or not, mod or not. But the manufacturers are in it for profit and sales...not optimal performance. They make what will sell, make profits, and keep them out of litigation. There is almost always plenty of performance left available through mods, and upgrades in most platforms.

I put ~$30K in upgrades in my 997 Turbo and made it a beast, and never had any issues with it at all over a number of years....in fact....Still running perfect. Some guys were nearing 1000 HP in the 997 TT 3.6L Flat 6... Only had to install stronger connect rods and head bolts to handle it...

To each his own....But mods in many cases improve the cars with no harm (of course if you over do it....different story.
DC

 

I broke my diff and output shaft on a very small dip going 30mph wot. The dealer tried to get me on VAP springs. I fought them for a week, and they replaced it under warranty. The suspension travel from top to the bump stops is within factory specs for suspension flex, lowering the car should absolutely not have an effect on that as the car is within the factory specs travel. Now if I removed the bump stops that would be

 

Could you let us know what the diff fluid looks like after you get her back ?
Interesting Jaguar doesn't have this in their maintenance schedule since there have been some seal and diff failures.
Cheap insurance to change the fluids.

 

Not regards the differential on lowered vehicles, but how about the issue of bump-steer?

https://www.turnology.com/tech-stori...ump-steer-fix/

 

Having worked in various industries as an engineer including with all 3 major american automotive companies on different projects, of course marketing plays a large role in vehicle design no doubt about it.
Ford for example almost all trucks and suvs, 1 or 2 passenger cars and the mustang.
But not everything. Safety and reliability are top of the list. Nothing will sink a brand faster then something that kills you or falls apart quickly. Perfect example for anyone that was around in the 70's when american cars
were pure junk. All 3 major companies had to do a 180 going forward as the Japanese were killing them quality and reliability wise. It took them 20 plus years to shake that stigma of making junk.

Ford saved Jaguar from the Junk heap. They went in and fixed the reliability problems made some nice cosmetic changes to the models but keeping them unique to the brand. That's where good marketing comes in.

I still have friends at Ford and GM. Everyday passenger cars are approached differently from the higher end sports performance models. Those cars are optimized for legal street performance as much as they
can bare due to safety and emission/mileage regulations.

Again I am not saying modifying cars is wrong I have done my share. I am saying is that there is a lot of the drinking of the "coolaid" in the automotive aftermarket industry.

If you can afford to put 30k into your car and drive the HP up to 1000 hp and your happy go for it. I just don't know any streets or highways where I live you could use that kind of power
and not end up in jail or dead. 2 years ago guy in my area that owns 3 car dealerships bought himself a Ferrari a week later he was dead his manhood got the best of him so did the tree
on a curve.

Great forum and group of people. Healthy discussions with different ideas is always good.

 

That reminds me of a story I heard back in the 70s or 80s. Apparently only 7 models of a particular Ferrari were imported into the UK and a car mag decided to do a 6 month follow-up with the owners. Only one was still alive. Lethal cars in the wrong hands (I guess all cars can be that, but some are a bit less unforgiving).

 

Another story in the news just yesterday about a Lambo that didn’t survive 10 miles out of a new car dealership. Similar occurrences appear to be common. Wealth doesn’t cure stupid.

 

Haha. I have seen a ton of those stories as well....And agree, a fast car and a fool won't last long. Thankfully I reserve my "really" fast driving for the Air Strip shootouts,like Shift Sector, WannGoFast, and No-Fly Zone. Funny thing, is I have all this muscle/performance in my cars and drive exactly 3.2 miles to my office for work, and can rarely get over 45 mph. Kind of ironic.....Still makes me smile to know what they "can" do....And I just enjoy tinkering with them to make them look and perform better(and hopefully no plans to wrap a tree with any).

DC

PS...He ended up passing me by the 1/2 mile mark

 

Yeah sorry, in the case of lowering you should google diff risers sorry, my bad. With my previous car (BRZ) people over 1" who were into performance and safety was rising their diffs quite commonly. I personally have not a direct experience with this, because I never lower cars more than cca 15 mm. Over that, except the diff (non)issue, you starting to have aligment issues that you can feel for sure but thats a different topic.

EDIT: i would also like to point up to the topic, that even with VAP springs that I have no experience, you can read here that about 90% people say how great they are, and around 10% who says it made the car worse and unstable over ondulations. This clearly demonstrates that what is "good" and "bad" regarding performance on car forums are ultra-subjective and serously depends on abilities and experience of the car owners.

 

Mine has 68k miles on it 2015 F type S with regular track days, and nothing went wrong with the diff, never even had an oil change, but every-time I service it they check the diff and transmission oil for contamination.

 

So you've taken it to the new(er) Kuwait Motor Speedway? I went there for the Art Of Performance Tour a couple times. It's a nice track and the F Type did great around it.

 

I actually bought the car after I had a hot-lap at the Art Of Performance Tour of March 2019. it's a great car.