Should I put a flat washer on the rear diff carrier bolts?

[Michael L.]

Guys,

I'm installing the rear diff on the rear diff crossmember on my '69 coupe and the bolt kit I got from Paragon has flat washers in it for this. My assembly manual doesn't indicate a flat washer. The kit lists it as being for 63-79 cars so I'm guessing it was used in other years. I guess a flat washer isn't a bad idea and it won't be seen when finished. Should I use them?

Mike

[Joe L.]

Re: Should I put a flat washer on the rear diff carrier bolts?

Guys,

I'm installing the rear diff on the rear diff crossmember on my '69 coupe and the bolt kit I got from Paragon has flat washers in it for this. My assembly manual doesn't indicate a flat washer. The kit lists it as being for 63-79 cars so I'm guessing it was used in other years. I guess a flat washer isn't a bad idea and it won't be seen when finished. Should I use them?

Mike

Mike------


If you're referring to the bolts that retain the carrier to the cover, those bolts used a split lockwasher, not a flat washer.

As far as the crossmember-to-carrier cover bolts are concerned, the AIM specifies only a split lockwasher. This is true from 1963-79. However, I added a flat washer to mine. I use only SAE grade 8 washers, though, both flat and split.

[Timothy B.]

Re: Should I put a flat washer on the rear diff carrier bolts?

Mike,

The rear differential to cross member bolts should be grade eight and from memory be approx. 1 1/8" long with a flat washer. the cross member to frame bolts are also grade eight with just a lock washer.

[Michael L.]

Re: Should I put a flat washer on the rear diff carrier bolts?

Mike------


If you're referring to the bolts that retain the carrier to the cover, those bolts used a split lockwasher, not a flat washer.

As far as the crossmember-to-carrier cover bolts are concerned, the AIM specifies only a split lockwasher. This is true from 1963-79. However, I added a flat washer to mine. I use only SAE grade 8 washers, though, both flat and split.

Joe,

I'm referring to the bolts that hold the carrier to the rear crossmember. The paragon kit is #6314K. There are four of these bolts. The kit came with both flat and lock washers, I was inquiring about using the flat washers since my AIM doesn't call for them. Since they can't be seen after assembly and they can only add strength to the rear diff I'm going to leave them.

Mike

[Rich P.]

Re: Should I put a flat washer on the rear diff carrier bolts?

The rear crossmember to rear end housing bolts (4 of them) from 63-79 only used a hardened special thick FLAT washer. To use the original bolts and get the proper protrusion through the rear cover you can't use a lock washer. I have several hundred original crossmember to rear bolts and they all had the flat washer. Also every original unrestored car I worked on only had the flat washer. Check your AIM it will not say lock washer.

[Joe L.]

Re: Should I put a flat washer on the rear diff carrier bolts?

The rear crossmember to rear end housing bolts (4 of them) from 63-79 only used a hardened special thick FLAT washer. To use the original bolts and get the proper protrusion through the rear cover you can't use a lock washer. I have several hundred original crossmember to rear bolts and they all had the flat washer. Also every original unrestored car I worked on only had the flat washer. Check your AIM it will not say lock washer.

Rich-------


The AIM's from 1964-79 specify "L. Washer" which denotes a lock washer. However, the 1963 AIM specifies "P. Washer" which denotes a flat washer. Both 1963 and 1964-79 do specify the same part number----GM #446212. As far as I can determine, this was a flat washer.

[Gary R.]

Re: Should I put a flat washer on the rear diff carrier bolts?

On my cars I used common grade 8 bolts with a flat and lock washer and never had a problem. However, I am not a numbers guy per say but I don't know who will see those bolts?

[Timothy B.]

Re: Should I put a flat washer on the rear diff carrier bolts?

Rich,

My memory is telling me the plain washer is a thin version but I may be incorrect.

[Rich P.]

Re: Should I put a flat washer on the rear diff carrier bolts?

2016-09-01 15.05.38.jpg2016-09-01 15.05.55.jpg2016-09-01 15.06.10.jpg
The washer on the left is the differential carrier bolt washer the washer on the right is a normal bumper bolt washer both from 67. The thicker washer is the differential carrier Bolt.