Upcoming WInter Project - IRS/Rear Diff Build

[Fdawg97lx]

Hi guys, I'll be building my IRS over the winter and I'm starting to accumulate parts. Changed the fluid about 1500 miles ago and noticed a good amount of metal flake in the fluid. also noticing a slight howling noise is starting to develop. Its also leaking a little bit of fluid.

My plan is to instal the Full TIlt irs kit. I've also already got a spare diff from an 04 cobra and a used set of dss level 5 halfshafts and hubs.planning to go with ford racing 3.73's. I'm looking for advice on which differential, which cover, what install kit is best. Also anything that I am missing. Any advice is appreciated.

 

[Blkkbgt]

The only advice I can offer is plan on rebuilding your hubs/knuckles.

You're already going through all this trouble you might as well do them now.

Unless you've been re-torqueing your half shaft nuts yearly expect the hubs to be trash as well. You said you have spares but have you inspected them?

I went into my IRS last winter expecting to replace one half shaft boot and ended up rebuilding both knuckles. The hubs were also trash.

The best prices I could find on the hub bearings was at rockauto fyi.

 

[P49Y-CY]

if you're using the ftbr kit with the preferred lowering rear bushing, get one of their frpp covers that's already been modified for you.

also do a solid pinion spacer instead of crush sleeve.

tru-trac or wavetrac are a great lsd for street and strip

 

[Blkkbgt]

if you're using the ftbr kit with the preferred lowering rear bushing, get one of their frpp covers that's already been modified for you.

also do a solid pinion spacer instead of crush sleeve.

tru-trac or wavetrac are a great lsd for street and strip

Doesn't the FRPP rear cover require you to run less oil?

 

[hotcobra03]

I did 373s when I rebuild mine,,

Ours was a daily driver with mostly hwy high-speed

I went back to 355,

 

[P49Y-CY]

Doesn't the FRPP rear cover require you to run less oil?

yeah a little bit

 

[Fdawg97lx]

thanks for the info guys

if you're using the ftbr kit with the preferred lowering rear bushing, get one of their frpp covers that's already been modified for you.

also do a solid pinion spacer instead of crush sleeve.

tru-trac or wavetrac are a great lsd for street and strip

what is the benefits of using the ftbr kit with the lowering rear bushing??

I did 373s when I rebuild mine,,

Ours was a daily driver with mostly hwy high-speed

I went back to 355,

how much higher did the car rev on the highway? i thought it would be less than a couple of hundred rpm.

 

[P49Y-CY]

what is the benefits of using the ftbr kit with the lowering rear bushing??


it's to optimize the driveline angle

 

[Roots-type]

Auburn pro is a nice diff that has zero clunk. Locks hard and fast. Definitely recommend it over the ford racing piece.

Fluid/modifier- use whatever the diff calls for, not what the forums tell you.

Install kit- Ratech. part # RAT305K

As for 3.55 to 3.73, rpms will be just over 2100rpm at 70mph assuming stock tire height. In other words, negligible. 3.73 is a good gear choice that works well at both ends of a race. Can't go wrong with them.

 

[hotcobra03]

It wasn't so much the rpm increase,,

Gas went from 20mpg to 16mpg

Found I kept looking for more gears,, with 355s I still do

I did like ,,on stock motor .

It made the car more snappy,,

At 70mph hwy,down shift to 3rd would break the wheels loose

Just something to think about

 

[Fdawg97lx]

gathering the last of my parts for this build. I was planning on the true trac differential. i'm reading a lot about it and some people complain of noise. my car is street car that i drive aprox. 1000 miles per year in the summer with an occasional trip to the drag strip (maybe once a year). how noisy are these differentials when driving on the street?