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Drivetrain => Differentials, Axles & Brakes => Topic started by: Robert V on June 28, 2019, 01:22:48 AM

Title: Fact check 4 speed driveshaft length 1965 skylark
Post by: Robert V on June 28, 2019, 01:22:48 AM: Hello,
Up late tonight couldn't sleep.

A four speed solid driveshaft is 59 inches (length from center of "u" joint to center of "u" joint).

The 2 piece (automatic transmission) driveshaft is 1 inch longer at 60 inches measured the same way?

Thanks,
Robert
Title: Re: Fact check 4 speed driveshaft length 1965 skylark
Post by: Brian on June 28, 2019, 07:19:08 AM: What you stated is correct for a 65-66 Skylark GS with 401 engine.
With a 225/300/340 engine, the driveshaft is same length for ST300 auto, 3-speed manual, and 4-speed manual, and is same length as GS401 automatic driveshaft.
Now, does anyone know the correct length for a 65-66 Skylark GS with 401 and 3-speed manual trans?
Title: Re: Fact check 4 speed driveshaft length 1965 skylark
Post by: Robert V on June 28, 2019, 07:38:56 AM: Brian,

I measured 60 inches on my driveshaft. I am using a 300ST automatic driveshaft (rubber isolated) with a T10 4 speed on my 300 V8 motor. I became worried when I read specs for the 401 motor.

I was thinking about switching to a solid driveshaft if I can locate a correct one.

Thanks for clarifying.
Title: Re: Fact check 4 speed driveshaft length 1965 skylark
Post by: gssizzler on June 28, 2019, 11:54:51 AM: You want to be careful with this! A buddy had his GS converted to a 4 speed and when I talked to the guy doing the conversion,I discussed the importance of correct length and solid driveshaft with him! The length is important because you need slip or travel ! Well you can guess what happened! The driveshaft bound up in my buddies GS and broke the pinion in half at the yoke! In fact I was with him going to a car show! Luckily we were just pulling away from a light in town ( low speed) not going down the road at high speed! We or the car could have been severely damaged!, or could have injured someone else!
Title: Re: Fact check 4 speed driveshaft length 1965 skylark
Post by: gssizzler on June 28, 2019, 12:00:20 PM: Here are a few pics of the carnage! The shims and bearing are laying on the ground!
Title: Re: Fact check 4 speed driveshaft length 1965 skylark
Post by: Robert V on June 28, 2019, 01:04:36 PM: Thanks,
I've been running my drive shaft for over a year with a T-10 manual.
I was concerned because I recently read an article regarding a GS auto to 4 speed swap and it mentioned that the automatic driveshaft was 1 inch longer than a solid 4 speed driveshaft.

Brian posted info regarding the driveshaft length for the SBB engines.
I am OK with the length of my automatic driveshaft from my 300 ST with my 300 V8 motor and the 1965 BW T-10 manual conversion.
I gotta stop reading articles!!
Too much free time since retiring.
Robert
Title: Thanks for making the point! (Re: 4 speed driveshaft length 1965 skylark )
Post by: elagache on June 28, 2019, 01:46:50 PM: Dear Robert, Brian, Jon, and mid-60s Buick caregivers,

Quote from: gssizzler on June 28, 2019, 12:00:20 PM
Here are a few pics of the carnage! The shims and bearing are laying on the ground!

WOW! You can't make the point for a correct driveshaft length more potently than that!

Thanks for sharing the photos and I'm glad the damage was no more than that!

Cheers, Edouard :occasion14:
Title: Re: Fact check 4 speed driveshaft length 1965 skylark
Post by: jmos4 on June 28, 2019, 02:09:07 PM: Hi,

Best is to measure the lengths with weight on the suspension, and give the info to a driveshaft shop. As depending on if you have higher or lower springs and or suspension it may affect the length.

I had a issue with the wrong u-joint (Ford-no c-clips) and it came apart at 70mph, trashed the yoke and broke the ears on the trans (Muncie) so don't get rushed as was a expensive lesson.

Regards,
Title: Re: Fact check 4 speed driveshaft length 1965 skylark
Post by: Loren At 65GS on June 09, 2021, 10:09:26 AM: I realize this is an old thread, but does anyone have the correct length for a GS 3 speed drive shaft.

Loren