Just Installed complete differential housing assembly's (both used 4.88) into front and rear of my 85 4runner. I searched and can't find the answer to this question:

Question: If you hand rotate the front driveshaft (left and right)....what degree of rotational free play is acceptable before wheels turn? (This is different than ring and pinion back lash because it includes the carrier spider gears and manual hub (spline) with each contributing some free play. For this check, truck level, all wheels on ground, motor off, transmission in gear, 4wd NOT engaged but hubs are locked. The differential is an 8 inch 4cyl model with a factory open carrier (no locker)

I ask this question because rear axle driveshaft only rotates about 4-6 degrees freely each way, but the front rotates about 15 degrees. I assume this could be because the front axle also has the hub splines, but I am concerned this seems to be a lot.

Thanks in advance for any thoughts/advice

About 15 degrees of hand loose rotational free play

 

This play is within reason.
The only really important thing is that the ring and pinion backlash itself is small within the total play that you are seeing.

 

Thanks for commenting millball, makes me feel better. I wish I'd remembered to check the free play of the original front diff assembly before I removed it.. I guess the rear has less free-play since it doesn't have the hub spindles?....is that correct or is it just because the differentials / carriers worn differently?

 

There is a little lost motion to be expected in the hubs and in the birfield joints and spider/side gears, as well.
Even more if there is some sort of locker in the carrier.
I don't think you will have any issues running this.