Driveshaft length - 1/2" short... problem ?

[chargernut69]

My '69 Charger I am rebuilding came with a 51.50" driveshaft, apparently from a Roadrunner (?)...

However, it appears that the correct length for a '69 Charger with 440 engine, A727 auto, w/8-3/4 rear end is supposed to be 52.07"

My question is --  will this cause a problem ?    Can I still use it for a 500HP engine ?    any ideas / thoughts please .....


Thanks,
Jack

[Bronzedodge]

If it will bottom out and hit the output bushing or contact the tailshaft housing, it will cause havoc.

[John_Kunkel]

OP is saying his driveshaft is too short, not much chance of it bottoming out.

With the car sitting at ride height, what is the dimension from the rear end of the tailhousing to the center of the U-joint?

[Kern Dog]

There are factory lengths....THEN there is the real world. I have found a few published drive shaft lengths to be wrong.
The best way to determine a proper length is to measure the distance as My Kunkle wrote about above.
The proper technique is to insert a transmission yoke fully into the transmission, then pull it out one inch. With the rear tires supporting the weight of the car, measure the distance of the center of the U joint in the trans yoke to the center of the axle flange where the U joint will seat.
The car can be on a lift but the rear axle must be at the height and position that it will be when it is in operation.

[chargernut69]

OK...  my car is not assembled yet, so I guess I will need measure once I get to that point.   

If it is too short, I might have to resort to buying a custom one from Strange Engineering or similar.   

[John_Kunkel]

The proper technique is to insert a transmission yoke fully into the transmission, then pull it out one inch.

Won't work with the rear seal that has a dust boot. I prefer to use the factory dimension.

[Kern Dog]

Good point.   

[c00nhunterjoe]

The dust boot is flimsy rubber. It will compress easily to use that method of measurement.

[Birdflu]

The dust boot is flimsy rubber. It will compress easily to use that method of measurement.

[John_Kunkel]

Yeah, but what's the wisdom in running with the boot compressed and running on the radius of the yoke? Might as well just eliminate the boot but that exposes the seal to grit which will shorten its life.

[Birdflu]

Yeah, but what's the wisdom in running with the boot compressed and running on the radius of the yoke? Might as well just eliminate the boot but that exposes the seal to grit which will shorten its life.

I agree 100% with you in regards to running the drive shaft with the booted portion of the seal running against or into the radius of the slip yoke. Heck, without going to the shelf and measuring one, I'd bet the boot itself is + or - an inch itself. That being said, if the OP has a booted style seal, run the yoke into the transmission so that the boot is just short of running into the radius of the yoke and take a measurement.

[c00nhunterjoe]

Yeah, but what's the wisdom in running with the boot compressed and running on the radius of the yoke? Might as well just eliminate the boot but that exposes the seal to grit which will shorten its life.

I meant for the purpose of measurement, the seal will easily compress to allow you to bottom out the shaft in the trans.