High rolling resistance 8.75 gear pattern update

[70rrclone]

My car seems to have very high rolling resistance. I can barely push it in and out of the garage in neutral. After ruling out dragging brakes and disconnecting the drive shaft, it seems the 3rd member is very tight. I noticed it was very hard to turn by hand before i put it in the car. But figured since it supposedly didnt have many miles on it (bought used) maybe it would loosen up. Its a 742 case, clutch type with 3.55 gears. Is there a resistance value for the assembled 3rd member?

Thanks

 

[AR67GTX]

I think if the rear alone, (driveshaft out parking brake off, brake shoes backed off), has that much resistance internally, you would know it quickly from the noise. More than likely it’s just the cars weight and the tire size unless you have overlooked a tight brake somewhere.

Someone posted recently about different rolling resistance, forward and backward with a Torqueflite trans in neutral due to the rear sprag as I recall - but you say the driveshaft is disconnected. These cars aren’t light.

 

[Photon440]

Even when freshly rebuilt, it shouldn't have that much resistance. I think the shop manual states only 25-30 INCH pounds to turn the pinion, measured with the brake drums off and without front seal. It should be easy to turn by hand if the driveshaft is out and the wheels are off the ground. The 8.75 has a lot less internal friction than the Dana 60 or Ford 9 inch.

 

[R413]

That 25-30 in lbs is turning the pinion without a seal and no carrier installed.

If it is hard to turn the bearings could be too tight and it wouldn't need to make noise to have this happen.

Do you have disc brakes, they drag more than most.

 

[70rrclone]

It has 4 wheel disc. The pinion seal was leaking, i broke torque on the pinion nut to change the seal and of course the car rolled a lot better. I swapped the seal and retorqued to 240. Almost take 2 people to push it out on flat concrete.

 

[steve340]

If the diff pinion has a collapsible spacer you have probably got too much pinion bearing preload.

 

[R413]

Maybe need more shims on the spacer to lessen the pinion bearing preload. This doesn't change pinion depth, that one is under the bearing.

742 case =no collapsible spacer.

 

[Photon440]

That 25-30 in lbs is turning the pinion without a seal and no carrier installed.

If it is hard to turn the bearings could be too tight and it wouldn't need to make noise to have this happen.

Do you have disc brakes, they drag more than most.

The FSM specifies that the brake drums be removed to prevent drag for that test, something they wouldn't mention if it was without anything installed.

 

[70rrclone]

Im glad I pulled this thing apart. All of the bearings are bad. The shim stack for preload was home made and about .060. I think someone replaced the ring and pinion and the clutches and just stuffed it back together. Here are some pics. I did check the pattern before i pulled it apart. Not that it matters now. It has bowers bearing in it now. I wonder if there OEM 1966. Time for another order to Dr Diff.

 

[70rrclone]

The pn on the ringear says it for a 489 case and theres no spacer on the pinion

 

[70rrclone]

Ive heard of the thrust button on a 489 case but whats this?

 

[steve340]

Good move to pull it apart.

 

[R413]

Garbage! that's what it is.

 

[70rrclone]

I have all my parts finally. Heres the current gear pattern. Where do i go from here.. backlash is .006 with .104 pinion depth.

 

[steve340]

Go to the factory manual or there is plenty of info on gear patterns on the internet.

 

[dvw]

You need less marking compound. Also more load on the ring gear while turning. I use a drill to turn the pinion while using a fiber stick to load the outer smooth area on the ring gear. It's hard to see the way it is. But it appears the pinion is too deep.
Doug

 

[john-9]

first off -- the pic shows the thrust button for the clutch style sure grip ,, Bower bearings and Timken were used in factory set ups by the condition of the one you show that is an original bearing and needs to be changed out , as for your gear pattern it needs to move up on the drive side so take .003 out from the pinion depth locating shim and recheck the pattern , if the pattern is improving take another .003 out and recheck till you see a well centered pattern on the drive side . once the gear pattern is corrected this will change the thickness of preload shims needed to set the pinion bearing preload 20-25 in/lbs new bearings , 8-15 in/lbs used bearings. pic shows shape / location of gear pattern on new 3.55 i did yours should be similar but used gears will be slightly different in shape

 

[AR67GTX]

I have all my parts finally. Heres the current gear pattern. Where do i go from here.. backlash is .006 with .104 pinion depth.

View attachment 1718379

View attachment 1718380

Probably a bit too much pinion depth but listen to dvw and that pattern example John-9 posted looks really good.

 

[dvw]

Should look like this.
Doug

 

[70rrclone]

So far this is as close as ive gotten so far. Current depth is set at .090.