1985 Front Axle Center Section Path Forward

I have been chasing driveline grumbles since getting the R2.8 installed. Truck is a 1985 110 originally a 2.5NA. Since the truck had original propshafts with play in the slip joints, I replaced both front and rear with Tom Woods units.

When removing the front, I found the front pinion castle nut had slipped loose. It was still retained by the carter pin, but there was a good 1/8 inch play in the washer underneath it. That means the pinion was vibrating against the crownwheel, which couldn't have been good. I don't know how long it was that way. The pinion bearing did not sound terrible. This has me thinking about what path to go with the front center section and what I should be worried about. I know this truck had never even approached 70mph until it had the R2.8, so the driveline had never seen these kinds of stresses. I tightened everything up, put the carter pin in correctly so everything is secure for now and my odd grumbles are gone with this and new prop shafts. There is definitely some clunk in the front pinion now, though.

I have done a lot of work on the front axle. New swivels, new cv's, new axles, new bearings, new discs and calipers. Basically everything is new and put in by me, except I did not take out the center and did not pull the spider gears. At the time I did all the work, I still had the 2.5NA and when I put in new axles I couldn't feel any play in the spider gears. Even now I have the 4 tab flange (older series type) and there isn't any real play in the flange, but the pinion was bouncing around. Based on my sample of one truck, new 4 tab flanges arent like perfectly tight on pinions anyway.

Are the older axles ok for handling highway speeds so that I can just plan on a new center section? Should I convert to later style center section or change the pinion flange to more splines? Am I worried about nothing?

I am not a hardcore wheeler. I do however want to be able to tow our camper on dirt or highway. Truck trails and intermediate dirt roads. This truck will never exceed 70mph.

Follow on questions - I have a salisbury rear. I've done everything to that, including the spider gears and converting to discs. Are there any 70mph+ issues I could address here? I felt a lot of play in the rear spiders when I put in new axles, so I did them at the time. I don't think I have any issues here, just looking for anything that would give more reliability or smoothness.

I realize these trucks are not smooth, I'm just looking to have things up to as high a standard as is realistic.
For peace of mind and to reduce backlash, I'd pull the axle apart and inspect all components for wear. Then reassemble everything properly with attention to pinion height and backlash. I'd also consider upgrading to a 4-pinion diff or ATB since your use-case includes towing on dirt with the torque of a R2.8. If you can't afford the down time, I'd look for a Discovery 1 axle to rebuild and swap in.


Well-known member
If you want to see what end is the issue, lock the center diff and pull the front prop shaft (drive shaft) and see if it goes away. But swapping the whole front diff is not hard, early trucks (93 and down) have ten spline inner front shafts so you need that style diff.
The grumble went away after tightening the castle nut on the front pinion. There is still slop, but I wont be able to tell if it's in the transfer case or the front axle. Pulling the front center isn't too hard - I'll do that next.