C2 Differential Pinion Nut Torque Spec???

[James W.]

I read in the 1963 shop manual that the toque on the pinion nut should be 15 to 25 in/lbs for new bearings. What is the proper way to install the nut and run it down before taking this torque reading. We are reassembling a 1965 differential and want to be sure it is correct.

Thanks,

James West

[Duke W.]

Re: C2 Differential Pinion Nut Torque Spec???

That's not the nut torque. It's the pinion bearing drag torque. You tighten the nut until you read 15-25 lb-in drag torque while turning the pinion with a 25 or 50 lb-in torque wrench.

Usually you can progressively "bump" the nut with an impact wrench and keep taking drag torque readings until you are in the range.

Duke

[James W.]

Re: C2 Differential Pinion Nut Torque Spec???

Duke,

Thanks for the quick response. I have a few other questions or assumptions regarding this.

The differential is installed in the frame (body-off) at this time. I assume that we can achieve this drag torque spec as it is installed?

Do we need to have the differential filled with gear oil or doesn't this have any effect on the final torque reading?

Thanks again,

James West

[Terry M.]

Re: C2 Differential Pinion Nut Torque Spec???

Jim,

I believe, without reading the shop manual, that drag torque value is for the pinion bearings and crush sleeve only - that is no ring gear or side bearing load, and of course no half shafts or trailing arm bearings either. Of course no oil either, although I'm not sure how the oil would affect the reading. This is intended to be a test of the pinion bearings and crush sleeve only. It sounds like you are well past that point.

[Duke W.]

Re: C2 Differential Pinion Nut Torque Spec???

Pinion bearing drag torque is set without the differential case installed with the pinion bearings lubricated with SAE 80-90 GL-5 gear oil. After installation of the case a check should be made of total axle drag torque, and the spec should be in the book.

If the pinion nut is removed, say to replace the seal, its radial orientation should be marked and then the nut installed to the same position and maybe a hair more.

It's not clear to me what operation you have performed that required tightening the pinion nut. It would be helpful if you explain what operation you are performing.

Duke

[Gary R.]

Re: C2 Differential Pinion Nut Torque Spec???

As Duke said the torque range is for lubed pinion bearings only. I keep them in the 15-18 in/lb range for new bearings. Total drag with case preloaded is between 25-30 in/lbs. You have to be careful not to overcrush the sleeve or you have to replace it. The GM sleeves were much harder to crush then the aftermarket ones. With the A.M sleeves they crush very fast once you get them going.

[James W.]

Re: C2 Differential Pinion Nut Torque Spec???

Duke,

Sorry for the delay in my response, I've been out of town since last week. To answer your question as to what was done to the differential. It was disassembled and recently overhauled. We are at the final stages of the overhaul and could not find the spec for the pinion nut. As I said the differential case is installed in the chassis (body-off) pinion nut lightly ran down with a impact and the case has been filled with gear oil. We have not attached the half shafts. We are now ready to check the drag torque per the shop manual specs.

Are we correct in that we should get a total drag torque reading of 20 to 25 in/lbs. in the currently installed configuration?

Thanks,

James West

[James W.]

Re: C2 Differential Pinion Nut Torque Spec???

Duke,

Sorry for the delay in my response, I've been out of town since last week. To answer your question as to what was done to the differential. It was disassembled and recently overhauled. We are at the final stages of the overhaul and could not find the spec for the pinion nut. As I said the differential case is installed in the chassis (body-off) pinion nut lightly ran down with a impact and the case has been filled with gear oil. We have not attached the half shafts. We are now ready to check the drag torque per the shop manual specs.

Are we correct in that we should get a total drag torque reading of 20 to 25 in/lbs. in the currently installed configuration?

Thanks,

James West

[Duke W.]

Re: C2 Differential Pinion Nut Torque Spec???

The pinion nut should have been tightened to achieve the proper pinion bearing drag torque before the case was installed.

I can only suspect that the axle overhaul procedure was improper. My suggestion is to remove the axle, drain the oil, remove the cover and case so only the drive pinion remains in the carrier. Then accomplish the pinion bearing preload task and properly assemble the axle including setting up side bearing preload and ring and pinion backlash.

The proper overhaul procedure is in the '63 Corvette Shop Manual and later CSMs. You should also read the two-part article on side yoke end play and axle overhaul that I co-wrote with Bill Bradley about two years ago.

A proper;y assembled axle should last a long, long time. Improper assembly can result in short axle life.

Duke

[Michael H.]

Re: C2 Differential Pinion Nut Torque Spec???

James,

I agree with the Duke. Pinion brng load must be measured without the diff case/ring gear installed. When overhauled, were the pinion bearings and crush sleeve replaced? Makes a big difference in the results.

On your red/red 64, if original, were the dash panel tabs and rivets originally painted gloss red? Thanks.

[William V.]

Re: C2 Differential Pinion Nut Torque Spec???

James

The 15 to 25 in/lbs is the preload on the pinion bearing (new bearings installed). It is checked with the pinion only installed. I never us an impact for this process I feared damage to the bearings or race. What I have always done is tighten the pinion nut squeezing the crush collar until there is no in out play and then tighten the pinion nut a little at a time (1/16 to 1/8 turn)until a preload reading of 17 to 18 in/lbs. If over tightened, the pinion needs to be disassembled and a new crush collar and pinion nut installed. Do not back off on the pinion nut.

Bill