Just had a new 949 Giken diff installed in the car along with new bearings, seals, and the proper fluid. The diff seems to operate properly while on track. However, when I make a tight turn at low speed (say 2nd gear) I hear a thump thump noise coming from the rear of the car. The axles and wheel bearings are relatively new. I don't see any unusual play in the drive shaft or axles. Has anyone with a Giken diff had a similar experience? Any ideas?

 

My OSGiken only clunk and thumps when it's cold out. After a mile or so or once warm outside it operates smoothly.

Is this after sessions?

 

I've got about 500 miles on mine and it has zero thump at any time regardless of temp. Are you using the OSG fluid?

 

Yup. OSGiken fluid, usually occurs for me when it's <45°F

Maybe I need to take the diff out and have a shop adjust/inspect the lash

 

You need to replace the fluid. Any time the giken makes those noises, change the fluid. (Im assuming it was installed correctly. Contact Ben at Puddy Mod Racing with any questions about your install, break in, maintainance...)

Also, dont waste your money on the giken fluid, motul 75w\140 is half the price and works well.

There is a very specific break in procedure, then you change the fluid. IIRC 20 minutes of low speed 10-15 mph tight figure eights, and 200 miles, on a brand new giken, or new clutch packs, then change fluid.