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88-95 14bsf axle swap

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thaboss801

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Alright I have not found any definitive answers by doing searches all over the net.

I have a 84 k5 I am swapping in a 88-95 14bsf in. They are plentiful in our junk yards. I'm not scared of the perches all that's easy.

I know that the ifs axle shafts are longer than the solid axle trucks. Are the ifs 8 and 6 lug axle shafts interchangeable?

Different backing plates and hardware? I know I'd have to change brake shoes to the skinnier 6 lug shoes.

Any info would be awesome thanks guys
 
I did part of a hybrid of the two axles.

I found a full set of 3/4 ton axles from a 89' suburban with 4.10 gears.

The front is identical to my 89' 1/2 ton axle so I just swapped everything over from the knuckles out (to change over from 8 lug to 6 lug). The axle shaft also had the same spline count as the 3/4 ton. So, the front was easy.

The rear was an 8-lug in it's original case. I went to the junkyard and took the (88-95) 6 lug axle shafts, backing plates and drums. The major difference was the older, 8-lug axle shafts are 1/2" shorter than the newer 6-lug. So, I bought 1/2" thick backing plate spacers to move everything correctly. Other than that, everything bolted right up. Spring perches and shock perches were identical to the blazer.

And when all was done, I still had 6-lug axles but now with 4.10 gears. The width of the rear is now almost idential to the front. Took a little getting use to but I'm good with it now. I did also change out the wheel studs in the back too.

If you want to still stick with the 88-95 era 14SF's, there are two widths. Once is close to your existing one (if I recall about 64" wms to wms). And the wider one is about 67" which would match about the same width as your fronts.
 
What I have read most recent is that if the 8 lug has the 11 in brakes the 6 lug axles and drums are all you need?

The different width axles are only between 2wd and 4x4 so I'm good there.
 
thaboss801 said:
What I have read most recent is that if the 8 lug has the 11 in brakes the 6 lug axles and drums are all you need?

The different width axles are only between 2wd and 4x4 so I'm good there.
Click to expand...

You need the 6 lug backing plate as well.

Here is what I did on my truck (this is actually another members but identical to mine).

shot 1.JPG

shot 2.JPG
 
Those pix are my truck and I've built the '84-'91 14SF to 6 lug more than a few times. Showed Jeff the way thru some of the build for his but it's really straight forward.
I like doing it this way for the very reason of not having to cut perches and shock mounts. '84-'91 14SF are every where and dirt cheap with 3.73 & 4.10 gears. 4.56 were an option but rare to find.
Plus you can do the entire thing in one day.
Anyway...
The 88-'98 14SF 2wd are too narrow. 4wd on spot but the 4wd version is pretty rare and not cheap.

The '84-91 14SF used two brake sizes but that is of no matter to you if you are going to 6 lug. Find the axle with the ratio you want and go from there.
You'll be tossing out the 8 lug axles, drums & backing plates.

Use the backing plate for '88-98 14SF 6 lug axle. You can use 2wd or 4wd as they are exactly same.
The shoes are same as 10 bolt 6 lug.
You need to use the '88 up wheel cylinder as 10 bolt cyl are at an angle.
Your current K5 10 bolt steel brake lines bolt in '88 up wheel cylinders.
Use '88 up 6 lug 14SF drums, 2wd or 4wd.
I use aftermarket '88 up 4x4 14SF axle shafts (not 2wd!) when I do them as it's cheaper in the long run instead of spending gas & time searching for used 4x4 axle shafts.
Axle tube size never changed from '82 thru '98 on 14SF so bearings and seal are all the same part #.

Lastly a pair of 1/2" spacers for moving out the back plate. $30.

Not sure what other info you want but let me know if need anything else.
This is how mine lines up now. Tracks way better.
IMGP0200_zpsb545e82b.jpg
 
Do you happen to have the axle seal part number? This of course assumes that since tube diameter didn't change, the seal should always be the same.

That is good info in your post, I noticed when building mine that there were all sorts of different seal part numbers (and dimensions) for the 9.5". I bought one, and while it fit the axle fine, it was not tight in the axle like it should have been. I RTV'd it in place, but I know it's not right.
 
What's the differences between 2wd and 4wd axle shafts?

I was planning on finding a 2wd rear axle. As there are more of them in the yards than 4wd.
 
88 & up 9.5
4wd axle shaft = 33-1/8"
2wd axle shaft = 31-13/16"


My drunken reply might have been a little off. :D
Bearings same, seals aren't.
The seal I use for '81-'91 diff is National 3747 and National bearing R1561TV fits '81 thru '07. The '88 up uses National 710105 with tube bore 3.080" vs 3747 with 3.084" tube bore.
You need the seal to match the housing. As to why the seal OD/tube ID size would change, cant say for sure. OD of the tubes are same @ 3.5"

I used after market axles for '88-98 6 lug 9.5 but they were exactly same OD as 81-91.
Bearing surface OD (8 or 6 lug) 81-'98 is 1.706" and the 3747 seal is 1.703".

Another thing I noticed I said is the brake tubes. Use the brake tubes off the 9.5. The steel tubes are too short from the 10 bolt.

One more thing to keep in mind the stock 88-98 use a 14mm lug studs. I upgraded to 1/2-20 lugs all the way around on my truck. Requires some drilling but nothing major.
 
A quick update to finish up the thread:

I found a 4.10 14b sf 88-up rear end in town from a recycling yard. Install time was 1 day with a plasma cutter and mig welder.

Swapping into the 84' K5 my parts list was pretty low:

Conversion u-joint s44 to 1350 joint

RuffStuff 14 bolt swap kit

I got a complete assembly with brake lines and everything matched up with the factory T-fitting and flex hose (As long as your lines break loose). I need to figure out the emergency brake lines but they look as though they will switch over from the factory 10b.

For the most important part now, how it looks!!!


ImageUploadedByTapatalk1386198403.141018.jpg
ImageUploadedByTapatalk1386198413.949720.jpg
ImageUploadedByTapatalk1386198435.500432.jpg
ImageUploadedByTapatalk1386198446.844291.jpg


This should last up a lot longer to the carb'd 454 under the hood!

ImageUploadedByTapatalk1386198403.141018.jpg

ImageUploadedByTapatalk1386198413.949720.jpg

ImageUploadedByTapatalk1386198435.500432.jpg

ImageUploadedByTapatalk1386198446.844291.jpg
 
IIRC, the 10 bolt cable ends can just be pulled out of the 10 bolt and swapped into the 14SF. I know I've got all factory e-brake components on mine.

What year is your truck? I have the "early" e-brake style that runs down both sides of the truck, I will be converting over to the later style, it's cleaner and less of a problem with drivetrain/exhaust components, FWIW.
 
thaboss801 said:
I did use a 4x4 rear end because of the added width.

Personally I don't know why you'd want to convert an older 8 lug 14bsf to 6 lug
Click to expand...

Mainly just to keep the existing rim/tire combo you have without buying new 8 lug rims. Worked great for me....:waytogo:
 
jeff in co said:
Mainly just to keep the existing rim/tire combo you have without buying new 8 lug rims. Worked great for me....:waytogo:
Click to expand...

Yeah I guess it really comes down to if you have a welder to put new perches on the newer axle. I was able to get bigger brakes and keep my 6 lug rims
 
For those that care, the wider axle (even with my narrow 10.5" tires on stock wheels) allows a fair bit more junk to be slung up the side of the truck.

I don't care, but if I were towing a trailer as wide or wider, it would get thrown all over it, even with mudflaps. As it is I have a trailer that is narrower, so it doesn't matter.

You can see in your pics where the tire sits, if you look at a stock setup at the same rear view, you'll see the difference. Still, far better axle. :)
 
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