So seeing as my truck is going to end up with a fresh motor and transmission in the months to come, I got to thinking if I should pay any attention to the rear end.

I’m starting with an 8 3/8? with what I suspect is 3.55’s inside, but would like to stretch the gears out some for highway use. As well as delete the one wheel peel action I’ve got going on. So I was thinking of upgrading to a Trac-Lok / aftermarket rebuildable lsd and changing the final drive out.

Anyone care to chime in on the basics of picking the parts? From what I can tell I simply buy the diff that fits my housing/ spline count, and buy a corresponding ring and pinion in my preferred ratio. Assemble, measure, install, drive?

 

Are you putting in a 727? I think going with a A500/46rh would give you overdrive and eliminate the need for new gears.You would have to move the trans mount back and shorten the drive shaft. You still could put a limited slip in the rear.

 

3.55s are great for highway use. For traction you can just put a Spartan, Lock Right or Aussie locker in the open carrier.

 

being an 86, and built before Dodge started using overdrive/ I am doubting your 3.55s (though it is entirely possible, Dodge did use that ratio for years) I'm thinking you have more like 2.94-maybe 3.23. could be as low as 2.76. if the tag that was bolted under 1 of the rear cover bolts is no longer there, the ratio is stamped on the ring gear within the rear end. and it is entirely possible to add a Track Lok to your current rear end.

 

Nah, just going through the A-999 enough to freshen it up, and repair a couple leaks. I actually like the three speed with lock up converter, just trying to drop my cruise rpm a bit, and have functional traction for bad weather, loose surfaces. Swapping to a trans that requires fab work isn’t really what I’m looking for on this truck.

Thanks! I’ll look into those and see what they offer. And don’t get me wrong I like the ratio in there now, I just travel in areas where the majority flow of traffic’s 45-80 and would like to be sitting closer to 1750-1800rpm at 65mph instead of 2500rpm +/-

Yeah, I know I don’t have overdrive. I’ve got the A999 with the lock up converter, part throttle unlock, and heavy duty extension housing. Below is the ratios chart. And since I didn’t want to open the rear end to “know for sure” I just mathed it and figure it’s probably 3.55 based from shift mph from 1st to 2nd.
As far as adding anything to my current, I may still do that. Just seeing what conventional wisdom is floating around. Plus since I’m already in there and have never liked the rpm at 65-70 figured longer final drive might be nice.

as a side note from what I can tell, unless I want to scroll the local yards it’s about the same price to buy all new parts as it’s be to buy a unit somewhere online? Anyone have any retailer recommendations?