SLP Firehawk

iTrader: (9)

hello i ordered a midwest 9" and i also got the chromoly driveshaft from strang which was ordered through eric.

i am having a vibration issue at highway speeds and i have tryed everything including changing the gear set to a different gear manufacture.

i have tryed to diagnose the noise by removing the transmission mount from the crossmember and disconnecting the torque arm from the crossmember and i can still feel this vibration from the center console.

i have heard that the driveshaft could be 2 short my car is an M6 not auto btw so if anyone knows what the driveshaft lenght should be let me know thanks

SS1875

iTrader: (34)

Quick check of the slip yoke for proper length DS is no more than 3/4-1" out from the back of the tranny. I went an inch longer because my PST was too short. I found my receipt from Strange the parts numbers are U1699 (41 7/8"CTC ) and U1662 (yoke).

Eric had me measure from the center of the rear yoke to the back of the tail-shaft on the trans.

EPP

iTrader: (22)

Was your 12 bolt PST's length one inch too short for the nine inch, that is what the difference is on the Moser rears between the 12 bolt (and 10 bolt) driveshaft length and the nine inch? Bob

SS1875

iTrader: (34)

The PST was purchased for a 9" ( or so I thought) prior to actual purchase of the rearend NOT the 12 bolt. The only other thing I could figure was if there is a difference in length of the rear yoke on a Strange Center section and the Moser Center at the time.

SS1875

iTrader: (34)

Could also be wrong pinion angle or possibly the trans mount if you are using a poly version.

SLP Firehawk

iTrader: (9)

thanks for the info but the angle is correct and its not the trans mount because i've disconnected the mount from the crossmember and held the trans in place with a jack and it didn't change the vibration

i am thinking it could be the driveshaft because i have about an inch of play from bottoming out on the trans and the space in between the caps and the yoke. eric has told me it is the right size driveshaft but i narrowed down the vibration to either the rear or the driveshaft because i ran the motor and trans up to 120 mph without the driveshaft in the car and there was absolutly no noise or vibration and as soon as i put it back in the noise/ vibration was there again.

possible that the driveshaft could be short by 1/2 an inch????

either that or there would have to be a problem with the center section

EPP

iTrader: (22)

Measure using the top x dimension to see what your driveshaft length should be. 10 bolt and 12 bolt lengths generally end up at 44.25, 9 inch lengths generally end up at 45.25. Bob

SLP Firehawk

iTrader: (9)

ok thanks i'll need to get my car back on the jack stands to check this

ssvert99

iTrader: (26)

keep in mind that there are different measurements needed for different brands of driveshafts. the difference is the offset of the trans slip yoke. the only thing that really matters is the distance the trans yoke goes into the tailshaft housing. best way to check a driveshaft you currently have is the install it all the way into the tailshaft of the trans and measure the gap between the rear u-joint and the pinion yoke. this needs to be done after the pinion angle is set and the car(rearend) is at ride height. there should be 1/2 to 1 inch of gap if measured this way. less will cause possible trans/rearend damage, more could result in leaks and vibrations. when ordering a new driveshaft the "X" dimension from the diagram above is what the manufacturer's need for the most part.

SLP Firehawk

iTrader: (9)

eric just so you know i'm not doubting anything we talked about on the phone however i was just trying to get different situations from peolpe.

i did check the distance from the yoke to the bearing caps on the driveshaft and i have about an inch.

in a post above the user ss1875 has a 41 7/8 inch drive shaft and from my understanding you use a 41 5/8th would that extra 1/4 of an inch be an issue?