Rear end clunk after new diff - Northern California Ford Owners

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Posted by Stanced Stang (Member # 11891) on :

The car is my 85 gt 5.0 5 speed. The rear is fully Maximum Motorsports equipped with PHB/TA system. I just swapped in a new rear end. I also swapped to an FRPP aluminum driveshaft at the same time. The Driveshaft did not have a flange on the rear end side so I used a 1310-1330 conversion u - joint and my original driveshaft flange. The rear that came out was a Lincoln Mark VII. The new rear is Fox housing with (used) Ford 3.73 gears, (new) Yukon Dura-Grip diff, ranger axles, SVO diff girdle/cover and sn95 brakes/North Race Cars brackets. I set up the diff with my teacher who is an ASE master tech with experience with doing gears/differentials. The backlash and gear tooth pattern checked out good. We did not change/check the pinion depth(rear end already had 3.73s installed). The problem I am having is a clunk upon acceleration/low rpm deceleration. If you leave the car in gear and coast anywhere from 1300 rpm or lower (mostly when the car starts to buck) you can hear a very audible clunk from the rear of the car. You can also hear this noise when starting from a stop roughly (too much clutch too quick). My theories include incorrect setup of the gears/diff, diff cover hitting panhard bar bracket (not likely), driveshaft hitting floor or the brake rotors moving around on the axles because I don't have centering rings yet. Any suggestions are much appreciated.

[ 2014-02-16, 09:59 PM: Message edited by: Stanced Stang ]

Posted by Beastly GT500 TVS (Member # 9723) on :

Sounds like it could be a loose backlash. To check proper back lash you must have preload.

Posted by Tom Renzo (Member # 13165) on :

Sounds like to much BACK LASH. WHAT IS THE BACKLASH???????

Posted by Beastly GT500 TVS (Member # 9723) on :

quote:
Originally posted by Tom Renzo:
Sounds like to much BACK LASH. WHAT IS THE BACKLASH???????

does it make you feel better to correct me? glad I made your day. your welcome

[ 2014-02-17, 02:44 PM: Message edited by: Beastly GT500 TVS ]

Posted by 5.0 with some go (Member # 8248) on :

check the bolts on your rear control arms, since you installed a panhard bar , when I did my rear suspension after a few miles it started to clunk when you came to a stop or when you took off from a stop or hit a decent bump in the road, even though we torqued them to correct specs they still came loose after the first test drive. re-torqued them a little more then spec and no more clunk.

Posted by Tom Renzo (Member # 13165) on :

quote:
Originally posted by Beastly GT500 TVS:

quote:
Originally posted by Tom Renzo:
Sounds like to much BACK LASH. WHAT IS THE BACKLASH???????
does it make you feel better to correct me? glad I made your day. your welcome

Just wondering how PRE LOAD controls a clunk????????????????????????? Or how PRE LOAD controls back lash !!! Two competely different settings. WHAT PRE LOAD are you referring to????? side carrier pinion just Curious!!!! By the way i did not correct you all i asked was what the LASH WAS!!!!! I would assume it was checked and recorded!!!! So my question should have been what is the backlash set @ and post the numbers!!! Your Welcome!!!

The bellow rear axle has .006 BACK LASH. Measured @ 3 places around the ring gear. This is what i asked Sorry for the confusion. When doing any type of work like this all readings and adjustments are performed and logged on to the customers bill for future reference. Thank You!!

[ 2014-02-19, 04:13 AM: Message edited by: Tom Renzo ]

Posted by NORCALSTANGS (Member # 3706) on :

What's your backlash at
Sounds like its on the loose side of ford specs.
What gear oil are you using, thicker will quiet it down .
If using synthetic really clunky.

But as others wrote already double check all bolts and lower torque boxes for cracks.

And realize MM torque arm and suspension carry more sound into the interior, than stock rubber bushing and poly.

Posted by CalBoy101 (Member # 13131) on :

I'm not sure if these are still in use with your torque arm setup but if so look for worn out control arm bushings, especially the ones on the top of the rear end housing.

Those are hard to find but Ford Racing sells them in kit with new C-rings, its part number is M-4050-B . If you they are shot the easy way to take them out is drill a bunch of holes through the rubber part of them then they are easier to knock out.

Also get the rear wheels up off the ground and get under the car and on each end of drive shaft twist it and shake it up and down and side to side hard with your hands and look for slop in the u-joints and front transmission bushing.

[ 2014-02-20, 04:32 PM: Message edited by: CalBoy101 ]

Posted by Stanced Stang (Member # 11891) on :

quote:
Originally posted by NORCALSTANGS:
What's your backlash at
Sounds like its on the loose side of ford specs.
What gear oil are you using, thicker will quiet it down .
If using synthetic really clunky.

But as others wrote already double check all bolts and lower torque boxes for cracks.

And realize MM torque arm and suspension carry more sound into the interior, than stock rubber bushing and poly.

We did not write down the backlash, but if i recall correctly, it was .008. I am using 75-90 with Ford XL3 friction modifier.

I did have a loose LCA bolt that I re-torqued to spec, otherwise all control arm bolts, TA mount bolts etc. are tightened to spec. The torque boxes are still in great condition, never been fixed.

Posted by Stanced Stang (Member # 11891) on :

quote:
Originally posted by CalBoy101:
I'm not sure if these are still in use with your torque arm setup but if so look for worn out control arm bushings, especially the ones on the top of the rear end housing.

Those are hard to find but Ford Racing sells them in kit with new C-rings, its part number is M-4050-B . If you they are shot the easy way to take them out is drill a bunch of holes through the rubber part of them then they are easier to knock out.

Also get the rear wheels up off the ground and get under the car and on each end of drive shaft twist it and shake it up and down and side to side hard with your hands and look for slop in the u-joints and front transmission bushing.

The torque arm does eliminate the use of the upper control arms, so nothing to be found there. the lowers are new MM adjustable arms, bushings are still good.

The driveshaft has a new rear joint, the front was not replaced. I have checked it since installation and it dosent seem to have any play. The transmission mount is a energy suspension poly mount that is also fairly new.

This is an issue that started after I replaced the entire rear end assembly. With my previous Mark VII rear end, I had no issues.

Posted by Stanced Stang (Member # 11891) on :

Removed diff cover today and i believe I found my problem. It looks like there is not near enough pre-load on the carrier bearings. I can shift the carrier side to side with my hand, no bueno if you ask me. We used the shim kit that came with the Ford Racing rebuild kit, which were the stack up type shims, one of the .005 shims was sticking out of the shim pack(towards the diff cover).

Posted by Stanced Stang (Member # 11891) on :

After having the rear end set up to proper specifications, I am still hearing the same noise. A friends suggestion was that the engagement of the splines on the driveshaft yoke could be loose causing a clunk. This is a used part which I have no history on. I did lightly pack the splines with wheel bearing grease, which did not do much. I also feel like the car has lost power, which I feel could be the brakes dragging. I went from a Lincoln Mark Vii setup to a SN95 setup. The calipers are used and have not been rebuilt. I am going to Knotts come hell or high water and would like to get this car back where it should be. Any and all help would be greatly appreciated.

Posted by Tom Renzo (Member # 13165) on :

First thing never use stackable shims unless the caps have ears. And even at that i never use them. You found out why as they come out. Also you did not do the proper carrier pre load adjustment as the carrier was to loose and that can mess up a new set of gears in just a few miles of driving. Soubds like you need someone who has the proper tools and know how to go over the instillation and correct what is wrong. Setting the pinion pre load correctly would make the input flange extreamly tight. If oit has play it was not installed correctly from day one and that could pose a big problem if the splines ore messed up. My suggestion would be to have a professional check it out and reset it or replace the damaged components. Thanks

NOTE!!!!! An 8.8 ford rear does not have previsions for a case spreader. So carrier setup has to be dun correctly and not for someone that is not versed on the procedure.

[ 2014-04-02, 04:05 AM: Message edited by: Tom Renzo ]

Posted by Stanced Stang (Member # 11891) on :

quote:
Originally posted by Tom Renzo:
First thing never use stackable shims unless the caps have ears. And even at that i never use them. You found out why as they come out. Also you did not do the proper carrier pre load adjustment as the carrier was to loose and that can mess up a new set of gears in just a few miles of driving. Soubds like you need someone who has the proper tools and know how to go over the instillation and correct what is wrong. Setting the pinion pre load correctly would make the input flange extreamly tight. If oit has play it was not installed correctly from day one and that could pose a big problem if the splines ore messed up. My suggestion would be to have a professional check it out and reset it or replace the damaged components. Thanks

NOTE!!!!! An 8.8 ford rear does not have previsions for a case spreader. So carrier setup has to be dun correctly and not for someone that is not versed on the procedure.

I did not like the stackable shims from the beginning, they are gone now. Like I stated in the last post, the rear end has been gone through by a reputable shop and any set up errors have been corrected. I was referring to the Driveshaft slip yoke on the trans end.

Posted by Tom Renzo (Member # 13165) on :

Ok that is a different story. It could cause it but i have never seen one do that. Not saying it can not happen but it is a very long shot at best.

[ 2014-04-03, 02:55 PM: Message edited by: Tom Renzo ]

Posted by REDLIGHTING (Member # 11296) on :

^^^ What's a ling shot??

[ 2014-04-03, 06:37 AM: Message edited by: REDLIGHTING ]

Posted by Tom Renzo (Member # 13165) on :

Sorry a LONG SHOT!!

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