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Author Topic: Swap F&R diff between 76 K25 and 81 K20 truck  (Read 1519 times)

Offline Mark

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  • driver is a 1981 K20, spares 1976 K25 & C25
Swap F&R diff between 76 K25 and 81 K20 truck
« on: September 10, 2020, 06:06:39 PM »
I have a 1976 K25 parts truck and wish to swat the F&R differentials into my 1981 K20 truck. My question is this doable or do I need to also change drivelines? The trucks have different transfer cases too.
Thanks for any help you can provide in this project
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Offline JohnnyPopper

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Re: Swap F&R diff between 76 K25 and 81 K20 truck
« Reply #1 on: September 11, 2020, 02:37:07 PM »
It will probably work, but what are you gaining?

Different ratio, lower miles?

If the 76 has a NP203 transfer case you'll want to install a part time Kit and locking hubs, or expect already bad mileage to be worse.

Are the wheel bases the same?

Inquiring minds want to know...
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1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction
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