hey guys, i have a 71 4dr that has a very funny rythmic vibration and hum that starts to kick in around 35-40mph and get really bad between 40-50. i have replaced the front end with polygraghite from pst and just had the transmission rebuilt and the engine has been thuroughly checked. what could this possibly be? the only thing left is the driveshaft and rearend. the rear end is stock. also is this an 8.8 or an8 inch rearend or are they the same thing. (5 lug w/ 302) if i need to rebuild the rear i would like to change the gears to something around 373's. any imput or experiences with this? the trans has a 3000 stall converter in it and has been built to handle 450 hp.i'm stumped any ideas:confused:
Your car has an 8 inch rear end, and no, it's not the same thing as an 8.8 inch. A number of things could cause a vibration... your driveshaft may need to be balanced, or the U joints could be worn. Tire condition can also be a big factor here too. Make sure your wheels are balanced properly and that the tires are not excessively worn. I'm assuming you have decent tires on the car so the next thing I'd do is replace the U joints, especially if they're original. Hope this helps... Sam
yes the tires are good as they are only about 9 months old and i tried the rotateing trick and no change. my neighbor works at a machine shop and we will be pulling the driveshaft to test it for true and to replace the u joints. what gets me is the fact that the vibration is not in sequence with the speed of the vehicle. i thought if the driveshaft was out the the faster i went the worse the vibration should get but it doesn't.do you know where to get rearend parts for an 8 inch. ford racing only stocks parts for 8.8 and 9's?
also could be a rear wheel bearing...had this happen to me. It was a very rythmic vibration that only happened at certain speeds. Possibly the center section has bearing problems also.
it is a very rythmic vibration that is part of what i don't get. you said this happened to you. what was the fix. did it invove pulling the axles or just a center chunk rebuild?
After you have checked the driveshaft and joints, I would pull the axles and rotate the bearings to see if there is any rough spots or even damage to them. Then rotate the pinion with them out(and the driveshaft disconnected) check for rough bearings and any excessive end movement on the pinion. Reinstall the axles and driveshaft, with the trans in park, rotate one axle slowly one way until you feel the slack in the ring gear etc. take up. Then the opposite way noting any excessive slack either way. May be just worn gears or in a lot of cases the diff. spider gear shaft will wear badly in the carrier. Usually that will cause a clunk noise when driving and stopping etc. You can get most parts like bearings at most auto supply stores, gears are available from Richmond or U.S. gear, through catalogs or online. With 3000 stall you need a bit deeper gear for best performance. One other thing I have seen is new tires that are out of round, broken belts or other mfg. flaws so I still would have them checked by a good tire shop on a spin balancer. Last in this long post is. Congratulations go out to Little E for his great effort in winning the 500, even tho it was not a Ford upfront, he did one hell of a job and deserves all the glory for himself and his father who trained Jr. and got him to the top.
hey old guy thanks for the advice. i will check it out and let you know what it turns out ot be as far as little E--- i asways was a gordon faneven though he drives for the opposite team but little E did drive the wheels off today and cough,cough did deserve to win thanks for the help
........"it is a very rythmic vibration that is part of what i don't get." Yep, thats what mine was doing and it was the wheel bearings but that doesnt mean that that is what is wrong with yours. Check out everything. If it is the axle bearings, you need to replace them. To replace the axle bearing, if that is the problem, just take the wheels off..remove the drums. Behind the axle flange you will see 4 bolts. Remove these and slide the axle out. Dont let the axle slide over the seals in the housing unless you are planning on replacing them. Take the axles to a machine shop or local garage and have them press the bearings off and the new ones on and reverse the process. Its pretty easy. Good luck.
Vibration Hey buddy I would almost bet 10 to 1 that it is your universal joints on your driveline. In my 64 Falcon Sprint, I have a non posi 4.11 rearend and was getting a weird vibration and it felt like something was out of round. I changed the universals and it was instant quiet and smooth. Anytime you get a problem with rearend vibrations always start with the driveline. I am no pro by no means but it sure saved me a lot of money and headaches. Hope this helps. Greg
Also check the tran. mount if loose or broke could be problem,easy to check.Check that bolts holding tran. to eng. are tight.
