BubbaG

Looking for a 8.8 diff expert to tell me what I am doing wrong.

I am upgrading a 1988 8.8 Traction-Lok to 31 spines, and changing from 3.55 to 4.10 gears. All the new parts are Ford Racing: M-4204-F318C differential, M-4209-88410 gear set, and M-4210-B2 installation set.

I am unable to get the appropriate gear pattern. As you can see in the first and third pics, the drive side is riding high and on the heel of the ring gear. At the same time, the gear is riding high and towards the toe side (see pics 2 and 4).

The original pinion shim was .032" and with that shim it was riding even higher and towards the heel. I added .011", and with this shimming, there is only between .010" and .011" between the head of the pinion gear and the differential housing, so I don't think I can move it any closer.

Backlash is right at .010". I decreased it to .006" which helped some, but is beyond the recommended range.

What am I doing wrong? How do I move the pattern nearer to the center of the ring gear (both between the heel and toe, and between top and bottom?

dawson1112

Shim your pinion a bit more.

BubbaG

Since I have already shimmed the pinion .043" and I only have about .010" clearance between the pinion gear and the side of the differential case, can I really shim it more?

According to Ford the pinion typically needs to be shimmed between .028" and .038" when using a Ford gear set. Is there something wrong with my setup that I am already over the typical shimming range and the pattern is still not correct?

dawson1112

Did you make sure the bearing cup was correctly installed into the housing and there is no crud or debre in the bearing cup housing? I guess Im missing somthing here. You say its close to hitting the case, but do you mean its close to hitting the case, or the carrier? You are shimming the pinion between the bearing and gear right?

BubbaG

I thoroughly cleaned the housing out with brake cleaner. I am sure that the race is seated against the housing, because when I first assembled it and had this issue, I took it apart again and used my bearing/race driver and made sure.

Maybe I'm not using the correct term, but currently there is only .010" to .011" clearance between the pinion gear and the case/carrier that the ring gear is bolted to.

Yes, I installed the shims between the gear and the bearing.

jwog666

shim the pinion out further as stated, at the dealer level we have a fixture to measure for the correct shim without having to install the pinion bearing on the gear. takes 5 min. at home, without the tool, its an exercise in time vampirism. once the pinion depth is set with the correct shim, then you can install the carrier and take a pattern. i have done a hundred or so, and have never had to change the carrier shims from stock when swapping gears as long as the pinion depth was set correctly FWIW

dawson1112

I know the frpp gives you an average pinion shim standard, but when its all said and done, wear pattern has the final determination.

jwog666

yeah, but since pinion depth is a measurement of case inconsistency, average isnt good enough for me. if the pinion depth is spot on you wont have to waste time changing side gear shims to set backlash and pattern. there are some aftermarket tool kits available to measure pinion depth in the case, not sure how good they are

mjr46

You need not do anything any of the previous posters recommended, aND i'LL SAY THIS ONCE..............PUT THE STOCK SHIM BACK IN!! AND set backlash to .008-.012........I have done tons of ford racing gears, they are prelapped and let me tell you none of them have ever given a pattern that is dead center on both the pull and coast sides.......you can change pinion shims until the cows come home and it won't line up.......Don't get caught up in the theroy..........I have had them where it has been high heel/low toe pattern numerous times and or reverse on ford racing gears and never had them make noise and I own the 800.00 dollar ford oem tool for setting up ford gears which always indicates to ues the oem shim when I have checked with the tool. Tooth contact has always been centered with such.............just run the oem shim and set carrier up with proper backlash and preload on the side bearings and you'll be fine!! the pinion shims I have used/oem ones have always been between .025-.035 .043 is too much..................end of point