I want to switch to 4.5 bolt circle.
The rearend in the truck was all rebuilt a few years back so I do not want to replace it with a another rearend in ? condition.
Will the axles from a 84 9.25 4.5 go into a 85 up 9.25 5.5?
I see a .1875 difference in the length,is this difference on the inside or outside of the housing?
Are the housings different between the said years?
I may redrill the axles to the 4.5 pattern if I have no other reasonable options.
I am on a tight budget so I am looking for the inexpensive but best way.

The 4.5" bp is for the 2wd. The 4wd went to 5.5" in 80.

Ive heard the axles themselves wont swap. Something supposedly changed with the clips etc.

I have been told that it won't work, but I did it in a truck several years ago. Had a truck with bad pinion bearings and a different axle with the wrong bolt pattern. I swapped the axles and drums from the "old" axle into the "new" axle and drove the truck. I believe I had to use the "C" clips that were with the axle shafts I swapped in.

Understand, this was a work truck that was abused, and was known to have carried a lot of weight some days. I drove the truck for about 3 years total, until something else broke (probably the trans, I had a habit of killing them), and the truck turned into parts. I really don't remember at what point in the truck's service to me the axle swap took place. I would guess it was fairly early in its service life, buying new U bolts on a truck that had served me for a couple years was not something I would have taken lightly. LOL!

I do remember an issue with the "C" clips at the time of the axle swap, seems with one set of clips, there was more play with the shafts then with the other set. I went with the set with the least clearance thinking at least the clips won't fall out. The mentality at the time was "I need this truck to work". I was a function over correctness sort of guy, and still am. Gene

Well the Year of the rear make a differance. If they were both 81-84/85 Yes they will dirrectly swap. They changed in 85/86

I think poorboy is on the right track with the c-clips

my lock right locker for the 9 1/4 has in the instructions that with the early sbp axles to use those c-clips and when going into the 85-up 9 1/4 use the c-clips and notes they are 2 different thickness.

myself, i would go a little further and maybe check the stock side gears/spiders to make sure they are the same or different to match the different c-clips.

would be good info to know if the c-clip change with axle is all thats needed... so far as long as I can remember it has been a no swap deal and all hear say...

man that would save a lot of work and $$$ when swaping wbp on the dodge trucks.

do the 8 1/4 axles inter-change axles from swb to lwb axles???

I have 2 of those 10 bolts so I guess a rainy day would let me find out.

Unfortunately, I'm not sure which way I swapped the bolt patterns any more, but the only newer 80s trucks I had were an 85, an 87 or an 89, but the newer rear axle could have been put under an older truck.... So many trucks, in so short of time, and so long ago. In a 15 year period, there were probably 7-8 Dodge trucks titled in my name, and probably another 10-12 that were parted out between me and my buddy, plus the 4 or 5 he had in his name. Parting cars & trucks funded my racing habit. This old age stuff sucks.

All I know is that buying new U bolts would have condemned the truck for at least a couple of years of service to warrant the expense, and the axle shaft swap would have been to keep using the original tires and wheels. Gene

I swapped in a 4.5" rear into a '91 D-150 and used the 5.5" axles. The C-clip is different in inner diameter and thickness, 5.5" is larger in both. Since the 5.5" C-clips are thicker, I ground them down on the side of a bench grinder wheel till they were the same thickness as the 4.5" C-clips. Of course, with no tone ring in the earlier housing, no more ABS.

I don't see how you could go from 5.5" to 4.5" without making new C-clips.

Just swap in a complete early rear.

Dr Diff

The correct way to do a swap is to swap the diff and axles together if they have a different sized c-clip than what you already have. you can just get away with swapping axles alone IF they had the same c-lips as what you currently have. Yes, in '85 they did change the c-clip size and yes, they are a bit different.

I asked Dr Diff about this sometime back and this is what he told me---and then I ordered a set of each c-clip from the dealer to have a look at them as I did not have extras around to compare. The difference is quite obvious.

Bottom line, the correct c-clips need to be in the correct matching differential and also have the matching axles.

and IIRC the spider gears have a different recess for the thicker C clips..