| FORD 8.8 AXLE INTO S-10 FACTORY 10 BOLT 7.5 INTRODUCTION NOTE: Other non-listed parts, years or applications may vary. Why change rears in the first place? Well, if you have been around the S-10 scene or have a little background knowledge of the GM 10 bolts, you will know that the factory 7.5 and 7 5/8 rears are pretty unpredictable. There are guys out there who have run 10's, 11's, 12's on them with no problem then there's guys who didn't even make it off the starting line with a stock 350 snapping an axle or blowing the diff. Overall, you could call it a pretty weak rear end, unless you have upgraded axles, swapped the factory posi-loc for an Eaton style, then you may still have a "time bomb". Personally, I decided on the swap for a few reasons. My truck came with an open diff and I couldn't pull any better than 2.4 X 60' times at the track, so the first thing I needed was a posi. Well after looking at my posi options and realizing how thin my wallet was, I had to come to a decision. I could either buy a factory style "time bomb" locker (G80 option) for $75-150, or I could buy Powertrax locker with unpredictable handling for $200-250, or I could dish out the dough on a quality Eaton posi for $300-350. Despite my worries of the posi's themselves, I was still using the puny 26 spline axles, unless I wanted to dish out more money on those and even then I would still have a relatively small and weak rear end which I could risk breaking and wasting all that invested money. The following reasons explain why I made the decision to do this rear end swap.
I had heard a rumor that Ford Explorer rear ends were similar in width and were supposedly a good match to swap. Their rear end has a ring gear of 8.8 inches and is just as strong as a Chevy 12 bolt. They also have massive 1.32" diameter axles with 31 splines. On top of that, the limited slip rears only come in 3.55, 3.73, or 4:10 gears. All 3 are pretty awesome gears for street/strip. Last but not least!!! - if you find one out of a '95+ Explorer, then they will have disc brakes - yes!! Then you would be upgrading strength, adding a posi, getting better gears, and making a huge rear brake upgrade to discs all in one swap - can you imagine the money saved from doing that to your 10 bolt? Unfortunately, there is next to zero in available resources out there, other than rumors on this swap, but knowing I had nothing to lose, I proceeded.
DOING THE SWAP SAFETY FIRST (See the last picture & topic below!) I took some measurements of my stock 2WD rear from backing plate to backing plate (48") as well as the spring perch measurements (38.5"), and a copy of my bolt pattern, then headed off to the local junkyard. The first one I found was a '92 Explorer sitting on some tires. I took the measurements and found that the 8.8 rear was about 3 inches wider from backing plate to backing plate and 0.5" wider from spring perch to spring perch. Close enough! I referenced the numbers on the tag and found it to be equipped with 3.73 gears and a posi. I was quoted the price of $175 for the complete unit with all the connecting pieces including the sway bar - I jumped at the deal. This is the rear end as I bought it. I drained the fluid to check out the internals. As you can see it's a pretty massive unit. 
This is the tag that you will want to check before you purchase the rear, so as to find out what internals the rear end contained. You will want to carefully check the bottom left hand corner of the tag. It may be difficult to see, but in you can see that it says 3L73. The 373 is the gearing, so it is obviously a 3.73, The L in the middle indicates that it is a limited slip (posi). If it had a space where the L is and it just said 3 73 then it would mean it was an open carrier. 
Here it is all cleaned up and painted. I sprayed it down with purple Castrol degreaser cleaner, then I used a wire brush attached to a drill as well as steel wool and sandpaper to get it smooth and clean. Finally, I coated it with 3 or 4 coats of high durability paint. 
Here is a comparison of the old Chevy 10 bolt 7.5 and the new Ford 8.8. The flanges facing rearward are for the sway bar to attach to. If you have heavy duty or thick shocks, you may need to trim the flange a little to allow shock mounting. 
The pinion depth is actually the same on both rear ends, which saves a huge driveline length modification headache. 
Here the diffs are lined up evenly to show the difference in width between the two. The Ford 8.8 is 3 inches wider overall, which gives about 1.5 inches extra length per side. Not bad, as you can make that up by wheel backspacing. 
One of the few changes you will need to make involves getting your Chevy driveshaft to mate to the Ford rear end. As you may have noticed, the Ford rear uses a disk style pinion yoke rather than the direct U-joint yoke. This problem is solved by getting the piece that mates to the disc yoke off of the driveshaft from the Explorer. Then you will need to buy a new U-joint, which has a set of both internal and external ends (internal for the driveshaft, and external for the yoke). This U-Joint is part #372 from NAPA. You could also replace the entire rear pinion yoke with a piece sold by M.O.R.E. (www.mountainoffroad.com) 
Another area of concern was the brakes. I was relieved to find out that it was simple enough to just use the factory S-10 brake line coupled to the splitter block. The lines that came with the Ford rear threaded right in. 
The last problem that I was aware of, was the bolt pattern. Since I have both my street tires and slicks mounted on Chevy rims, I didn't want to have to buy Ford wheels. The rear is already as wide as I want to go, so adapter plates were out of the question. I found a machine shop that would do the Chevy lug conversion for $80. Unfortunately, since my Ford rear end was from a pre-'95, it came equipped with drum brakes, but these ones stop better than my old ones did, and doing a disc upgrade would still be cheap and easy. 
Depending on the type of shock you are using, you may need to trim the plate where the sway bar originally attached to the axle. Since I used standard sized shocks, I had enough room so that it won't hit. If you want to use the sway bar, then you will need to relocate the bottom shock mount which is a simple cut and weld procedure. 
Here it is sitting up and in for test fitting. The spring perch location is approximately 0.5" wider than the 7.5, but there is no need for modification, I just yanked on the leaf spring a little and it popped right onto the stud. 
Looks good in there doesn't it? 
Gotta clean up the rest of the undercarriage now. 
Here's how far my tire sticks out now. This is with 3.5 backspacing though. If I increase it to 4.5" or 5", you would not see any difference. This makes it look a little more aggressive. If you're swapping it into a 4WD it will fit perfectly, as the 4X4 S-10 axle is actually 1" wider than the Ford axle is. 
Another profile shot. 
Stop looking at my rear! Goodbye old, hello new. 
Oh yeah! You can tell by the look on her face that she likes it. 
And remember...SAFETY FIRST!! Check out what happened when the strap on my transmission jack wasn't secure. The whole rear axle fell off and landed on my leg. It didn't break it, but I got some nasty swelling and internal bleeding. Put me down for a few days. 
WRITTEN BY: KNanthrup
EDITED BY: Dougofthenorth
92SonomaST
REV: 6APR05 | 
