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  #1  
Old 01-15-2002, 05:20 PM
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Default 14SF to 14FF conversion

Hey all! I'm a new poster but I've been reading for awhile now. Have a question for all the experts out there: Would I be gaining much by swapping in a 14FF to replace my current 14SF? I know the specs for both rear ends but I don't have any real testimonies (sp) about there stregnths and weaknesses. I do know the difference between the FF and SF but I gues the question is, is there much a real difference.

This truck ('85 K20) will be used mostly towing but no serious off road. I am planning to stay within the 33"-35" but nothing larger then that.

Also are there any good websites out there that cover a 83-87 Chev rear end conversion?

Thanks for all who help!

SS Rat

1985 K20,14SF,350,TH400
"The difference between genius and insanity is the level of success."
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  #2  
Old 01-15-2002, 05:22 PM
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Default Re: 14SF to 14FF conversion

<font face="Comic Sans MS">The 14 bolt SF has a 9.5" ring gear. The 14 bolt FF has a 10.5" ring gear. You lose more ground clearance with a 14 bolt FF. For that sort of duty you should be ok with the SF, in my opinion. The 14 bolt SF is roughly equivalent to the SF Dana 60. The 14 bolt FF is equivalent to the Dana 70... [img]/wwwthreads_images/icons/crazy.gif[/img]</font>

Tim "Sandman"


The one and only 'Sandturnip'
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Old 01-15-2002, 05:34 PM
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Default Re: 14SF to 14FF conversion

If it were me, with a tow vehicle, I would use the full-floater but I like to go a little overkill on things when the option is there. You probably don't really care about clearance under the pumpkin if all you're going to do is tow, correct?


[img]/wwwthreads_images/icons/wink.gif[/img]Somebody once said "Go Big" . . . Well we're goin' Full Size[img]/wwwthreads_images/icons/wink.gif[/img]
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Old 01-15-2002, 06:30 PM
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Default Re: 14SF to 14FF conversion

On a full floater the weight of the truck is supported by the axle housing and not the actual shafts, like a front end where the weight is on the hub bearings. The only load a full floarter deals with is the twisting force applied by the ring gear. A semi float has twisting force and supports the trucks wieght. A FF 14 bolt has bigger axles and a bigger rind gear so it is alot stronger, and it doesn't have c-clips to break and let your axle shaft slide out like the semi floater does. They are a easy change over just find one with the same gear ratio and you are good to go. A detroit locker is cheap for the full floater too.

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  #5  
Old 01-16-2002, 06:57 AM
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Default Re: 14SF to 14FF conversion

Any FF out of a 3/4 ton will bolt right in.
A 2 wheel drive one will require that the shock mounts be relocated but that is all.
Depending on what size the u-joint is is another factor.
If the caps on the yoke end are 1 1/16" it is a 1310 and will use a NAPA# 338, a cap that is 1 1/8" is a 1330 and will take a NAPA #447, 1 3/16" is a 1350 joint and will bolt right in.
If you do decide to do this you will also need new u-bolts.
$10ea at most spring places.
The axle tube diameter is 3 3/8" on a FF.
Even if the tube is the same size on the SF I would not reuse them, once the u-bolts are torqued down they stretch and it is a bad idea to reuse them.
I am not sure how the e-brake is routed on an 85 but on my 78 K5 the cables hooked right up.

78 K5 3/4 ton, 305, SM465/NP205, 33x12.5 EXT's.
No lift yet.
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Old 01-16-2002, 02:31 PM
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Default Re: 14SF to 14FF conversion

I've heard that most of the FF are 4.10 ratio. Since my ratio is 4.10, will I have much difficulty locating a FF 4.10? Also, what would be the average price I would pay at a junkyard? Rebuilt? New?

I appreciate all of you willing people taking time to answer questions! This really helps out alot!

1985 K20,14SF,350,TH400
"The difference between genius and insanity is the level of success."
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  #7  
Old 01-16-2002, 02:47 PM
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Default Re: 14SF to 14FF conversion

I believe most of the full-floaters came with 4.10s and some came with 3.73s. Around here, in SoCal, you can usually find 'em for around 200-300 bucks. I'm not sure what condition they're in though because I've never physically checked them out but I've seen the ads in classifieds and I've called a few junkyards looking for the semi-floater(cause I'm still a 6 lugger).


[img]/wwwthreads_images/icons/wink.gif[/img]Somebody once said "Go Big" . . . Well we're goin' Full Size[img]/wwwthreads_images/icons/wink.gif[/img]
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