But is the 78 a 30 spline?

 

i already know he is goig to like the 3.90's. it will be neat to see the dash light up for a while after the install. at least till he gets the ratio changed in the pcm.

 

Bad News!!!!@@@####****

Ran the truck around all week nice and easy and took her out for a real spin last night. Lined 'er up on the entrance ramp to I-49 and put the fat to mat. Awesome. Slowed down on interstate to about 75 and about 1 mile later Something starts to grind and howl like a train whistle. I cant tell if it is the rear end or transmission but I am fixing to go find out. Makes the noise when accelerating from cruise speed and above 45 mph all the time. Stops when you put it in nuetral and coast.

 

That sux! Can't be the rear end if it stops while coasting. Goodluck.

 

Damn, man I'm sorry to hear that. What kind of difference could you tell with them? Was it more "torquey"? Also, where at on I-49?

 

Put the back end on Jackstands and ran it in drive. It sounds like rear end but it is hard to say because of spintech muffler is loud. Checked pinion nut and its good and tight. I am hoping for rear end, at least I haave my old gears and diff to fall back on. I am still confused cant really discern where the noise is coming from and don't really care to crawl under it while its running in gear with the flimsy jackstands I've got. Going to try coasting in N down hill to see if it hums in N while accelerating if it does I think that may mean rearend.

 

Well, I sent my gears back to Randy's ring and pinion and they warrantied them out and sent me a new set. Not sure what was wrong. Well I got the new set put in with the help of a buddy and the Auburn to boot and all I can say is I love them so far.
Put about 300 rpm extra in OD so not to bad.