MustangWorks.com : Ford Forums - View Single Post - 1st differential install - what went wrong? Long and some dumb questions.

Mike Souslin · 05-07-2003, 12:20 AM

Well I don't know why my first post linked another topic but I'll try again!!!First of all, please excuse my ignorance - this was our first try!

I am helping my buddy with his car. We have the suspension completely finished and started working on the rear end of his 91 coupe. We are installing an Auburn Pro, Moser 31 spline axles and 3.73 gears.

Everything went pretty well, we thought. We got the backlash on the ring gear right per the gauge and the pattern on the ring gear was close (we thought). When we went for the test drive this is what we noticed. At first the car sounded really bad - almost like a bearing or something - It sounded much better by the end of his street so we figured eveything was just getting lubed up. It drove very smooth but there is a lot of gear whine, more so on deceleration. We brought it back in the garage and started the trouble shooting.

We are assuming that the pinion depth is not correct. Unfortunately getting the bearing pulled off and pressed on is an issue for us since we will have to go to a shop with a press each time we try a different shim. I've read on the net that some people heat the pinion bearing with a propane torch and then they can slide it off of the pinion - is this OK to do???? Secondly, we are not really sure how much to tighten the pinion nut. What we did was set the emergency brake to keep it from turning and then tighten the pinion nut just until there is not front to back play. Is this correct? How do you guy's keep it from turning???
Next - the bearing caps that hold the differential in, what direction do the arrows on the cap point? Towards the differential or towards the wheels? (I was not there when they were removed)

After the test drive we jacked the car up and when you rotate one wheel that is some play before it "catches" and you can hear a "thunk" when slightly rotating the tire forward and backwards. Does this indicate that the backlash is not correct? It is pretty noisy just rolling the wheel too?!?

This time we are going to make SURE that the pattern on the ring gear is correct before taking her out!

Thanks for any imput you can provide - I figure that this is the only way we will learn how to do it!

05-07-2003, 12:20 AM	#2
Mike Souslin Registered Member Join Date: Sep 1999 Location: Grove City Ohio Posts: 226	1st differential install - what went wrong? Long and some dumb questions. Well I don't know why my first post linked another topic but I'll try again!!!First of all, please excuse my ignorance - this was our first try! I am helping my buddy with his car. We have the suspension completely finished and started working on the rear end of his 91 coupe. We are installing an Auburn Pro, Moser 31 spline axles and 3.73 gears. Everything went pretty well, we thought. We got the backlash on the ring gear right per the gauge and the pattern on the ring gear was close (we thought). When we went for the test drive this is what we noticed. At first the car sounded really bad - almost like a bearing or something - It sounded much better by the end of his street so we figured eveything was just getting lubed up. It drove very smooth but there is a lot of gear whine, more so on deceleration. We brought it back in the garage and started the trouble shooting. We are assuming that the pinion depth is not correct. Unfortunately getting the bearing pulled off and pressed on is an issue for us since we will have to go to a shop with a press each time we try a different shim. I've read on the net that some people heat the pinion bearing with a propane torch and then they can slide it off of the pinion - is this OK to do???? Secondly, we are not really sure how much to tighten the pinion nut. What we did was set the emergency brake to keep it from turning and then tighten the pinion nut just until there is not front to back play. Is this correct? How do you guy's keep it from turning??? Next - the bearing caps that hold the differential in, what direction do the arrows on the cap point? Towards the differential or towards the wheels? (I was not there when they were removed) After the test drive we jacked the car up and when you rotate one wheel that is some play before it "catches" and you can hear a "thunk" when slightly rotating the tire forward and backwards. Does this indicate that the backlash is not correct? It is pretty noisy just rolling the wheel too?!? This time we are going to make SURE that the pattern on the ring gear is correct before taking her out! Thanks for any imput you can provide - I figure that this is the only way we will learn how to do it! __________________ 91 Coupe with fresh rebuild. Running Stage 2 Avenger heads (51cc chambers), Stage 2 cam (.549, .566)1.72 Crane Gold Race rockers, Port matched GT-40 upper & lower, 75mm Bullet MAF, 65mm Accufab TB, MSD 6AL, Long Tubes through off road and 2 chamber flowbastards. Stock T-5, 3.73 gears, Center Line Convo-Pros with skinnies up front. My baby is now bottle fed!!! Best time on the motor was 12.92 at 109.57. UPDATE - Getting Ready to install: Tremec 3550, Blowproof Bellhousing, Strange Shocks/Struts, Moroso Springs, Upper/Lower control Arms, 31 spline axles and new differential. After this..... 347 heart transplant and Rollcage.