Diff Strength

BOYRCR · Postby **BOYRCR** » Sat Sep 01, 2012 6:51 pm

As I work through the drive train I keep breaking things. I know this is bound to happen as you increase power (270rwhp intending on increasing). I upgraded the clutch (twin plate). Then I was breaking gear boxes. Three in total every time I accelerated in 2nd. So I ugraged the gearbox (quaife gear set). I purchased a Cusco 1.5 LSD to install in the 1.8L diff upgrade I had done previously due to breaking two diffs. I cracked the housing in the last one before I installed the 1.8L rear end. I had the feeling the diff centre was getting a little used as it was tightening up in low speed full lock turns and scrubbing the inside wheel. I was intending to swap it with the Cusco when it let go. Unfortunatly it let go and put a 6 inch crack in the rear housing and dumped the diff fluid when I was at the drags on Wednesday.

Has anyone had this issue when they have added more power or is the diff strong enough with an after market centre?

What are the guys with the V8 conversions using?

Any insight or experience would be helpfull.

Hjt · Postby **Hjt** » Sat Sep 01, 2012 7:09 pm

Unsure on the gearbox, but semi solid engine mound such as the AWR mounts take a large amount of the load off the gearbox. Vibrations increase however.

BOYRCR · Postby **BOYRCR** » Sat Sep 01, 2012 7:36 pm

Hjt wrote:Unsure on the gearbox, but semi solid engine mound such as the AWR mounts take a large amount of the load off the gearbox. Vibrations increase however.

Gearbox isn't an issue anymore due to the quaife gear set. But I will have to look into the engine mounts. Thanks.

toppertee · Postby **toppertee** » Sat Sep 01, 2012 8:23 pm

cadillac it!
http://www.flyinmiata.com/projects/LS1/index.php?UID=12

BOYRCR · Postby **BOYRCR** » Sat Sep 01, 2012 8:36 pm

toppertee wrote:cadillac it!
http://www.flyinmiata.com/projects/LS1/index.php?UID=12

I wonder when they will make it available?

toppertee · Postby **toppertee** » Sat Sep 01, 2012 8:45 pm

BOYRCR wrote:
toppertee wrote:cadillac it!
http://www.flyinmiata.com/projects/LS1/index.php?UID=12

I wonder when they will make it available?

Just get a holden diff (VZ ss)and mod it yourself,it pretty much shows you how to do it.

If not there is always the ford option.

http://www.flyinmiata.com/index.php?dep ... 20%208.8S1

Maybe have a look at the miata turbo guys and see what they do.

Good luck with it. BTW I would hate to be your rear tires!

bruce · Postby **bruce** » Sat Sep 01, 2012 9:15 pm

RX7 diff?

toppertee · Postby **toppertee** » Sat Sep 01, 2012 10:35 pm

bruce wrote:RX7 diff?

Same 7' ring and pinon.

Postby **NitroDann** » Sat Sep 01, 2012 11:40 pm

nope.

not all.

FC TII gearbox and diff makes the most sense and is probably where mine will end up.

Dann

Hjt · Postby **Hjt** » Sat Sep 01, 2012 11:56 pm

I wanted to say diff, typed gearbox sorry.

Good luck regardless, the mounts do still help the box, however your gear set is tough

davekmoore · Postby **davekmoore** » Sun Sep 02, 2012 12:08 am

Hjt wrote:Unsure on the gearbox, but semi solid engine mound such as the AWR mounts take a large amount of the load off the gearbox. Vibrations increase however.

Race engine mounts are fine on my daily driver. Noticeable but acceptable increase in NVH, mostly at idle.

flycasta · Postby **flycasta** » Sun Sep 02, 2012 10:49 am

270HP isn't the issue...... The issue is what you are doing with it.

As you said your problem is breaking things along the drive line......... The power/torque is finding the weakest link until it gets to the tyres, if your tyres have more grip/kg of car than the strength of a component then something will break. Drag racing is the biggest killer of drive line components and if it is only being done once or twice a year should be done with soft launches to avoid breakages. Classic racing guys have had to go back to an original clutch because when they use a twin plate or button clutch they break axles trying launch at 5 or 6 thousand rpm. Twin plate and button clutches put way to make sudden load on the drive line and don't allow enough slip for the smaller original parts made for a car with 150hp and will always break the weakest link..... in their case the axles. You are just finding out how much hp each component is capable of taking.

BOYRCR · Postby **BOYRCR** » Sun Sep 02, 2012 5:02 pm

flycasta wrote:270HP isn't the issue...... The issue is what you are doing with it.

I know the Main issue is my driving style. I am rough on the car. That's why I'm upgrading every thing as I go so I can do full rpm launches at the drags and flat change gears around a track.

I think I am going to install the Cusco LSD and see how it goes. If I have issues with the stub axles or centre again I will have to have a look at the Getrag diff and stub axles. I think they will be the strongest option and for around $2,000 + diff it doesn't seem that bad.

Mr Morlock · Postby **Mr Morlock** » Sun Sep 02, 2012 6:42 pm

its seems a very odd question to me. Things are designed as a package by engineers who actually do the calculations and have reference data. The modifier often finds out the limit when the component breaks or wears rapidly.

Postby **NitroDann** » Sun Sep 02, 2012 6:50 pm

I would just do a TII driveline swap.

FC 5 speed with adaptor plate or welded bellhousing, and one extra mount welded to the rear subframe, custom driveshaft and a rear gearbox mount, no PPF.

Dann