1970 Bronco Driveshaft Extension

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Jan 30, 2021 | 02:46 PM

JSavare

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Cross-Country

Joined: Jun 2020

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1970 Bronco Driveshaft Extension

Hi all, question about the rear driveshaft on my fathers 1970 Bronco restoration project. Truck is lifted 2.5 inches. The splines on the original driveshaft were locked up and shot, and he ordered a new one the stock length after reading that the stock length would work with our lift. After getting under it and going to bolt it up, it is about 2 inches too short. Our options are to buy a new one, or work with what we have now. He was quoted about the same amount as a new one would cost to extend and rebalance ours. Would it be possible to use a longer yoke to get that extra 2 inches or so either off of the transfer case or the rear? Does anyone make longer yokes? Would doing so change the angle to the point where it would cause a driveline vibration? Thanks in advance

Feb 2, 2021 | 02:19 PM

77&79F250

Moderator & parts slinger

Joined: Feb 2007

Posts: 50,194

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From: S/W Missouri, Polk county

How did you figure it was 2" to short? Like as in slide the slip yoke out when you went to install it and it came completly off? Do you have a CVC joint on the xfer case side? Since a new versus modded is the same. I would get new and flip sale what you have here. https://classicbroncos.com/forums/forumdisplay.php?f=27

I do not know of anyone that makes a longer yoke. Have you called around and got another quote from any other d/s-speed-custom-driveline shops? Are you 100% sure it is 2" to short. Remember that you need to to a flex check (compress and extend) the suspension to be 100% sure on that measurement.

Measure 5 times pay to get it built once.

The number 1 place to go for a d/s. Tow Woods. https://4xshaft.com/blogs/general-te...opes-vs-angles

https://www.dennysdriveshaft.com/fre...questions.html

https://www.driveshaftshop.com/driveshaft-measurement

https://azdriveshaft.com/how-to-measure/

Mar 4, 2021 | 08:40 PM

pttech

5th Gear

Joined: Jan 2008

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From: Wet Side

I'm going through the same process. Had old 5 leaf Duff springs under it and swapped for 9 leaf from Tom's. Now the drive shaft barely reaches the yoke on the rear-end. But I also have the body off so need to put a load on it to see where it will really sit. I've been reading that some of the 9 and 11 leaf springs cause the pinon angle to rotate down a little and that an angled shim needs to be used to get it to the correct angle. Doing that will shorten the required driveshaft length. My pinion angle is now about 11 degrees off from the driveshaft angle. Have not shimmed it yet, so hopefully that takes care of it.

Greg

Mar 23, 2021 | 11:56 PM

Boba Fett

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Joined: Oct 2005

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Since your 9" probably has a crush sleeve, you are way better off not messing with the yoke. You may be able to make up an inch with a longer yoke, but not what you need. Always measure the driveshaft. There are soooooooo many factors that affect this its unwise to just buy this or that.... Transmission, yoke, transfer case..... even if you "think" it stock, always measure what you have and compare to what if offered as stock before you buy...... The newest EB is over 40 years old.....