65 differential

All Models and Years
Rodders7762
Posts: 8
Joined: Sun Mar 11, 2018 10:04 pm

65 differential

Post by Rodders7762 »

Hey all

I know this has been a topic of much discussion and I have read a million articles already. My 65 has to be inspected and I took it to a shop that deals with a lot of classics.
The drivers side rear axle has quite a lot of in out play at the dif measured at between 25 and 45 thou of inch. It does feel like a lot at the wheel.
Does anyone have a spec for what the actual tolerance should be so I can give this to the garage or can I take any of this out by slightly tightening the adjuster ring on the dif?

I can’t find an official spec any where.... there must be one surely????

User avatar
thewolfe
Corvair of the Month
Corvair of the Month
Posts: 227
Joined: Thu Feb 27, 2014 4:01 pm
Location: Portland, OR

Re: 65 differential

Post by thewolfe »

There is no way to adjust the play in the axle stubs. The side adjusters are to set the position of the carrier in relationship to the pinion and they get preload set on the bearings so there should be zero play there. I would not recommend just tightening them up if you don't know what you're doing because there is a procedure for setting the whole thing up to get the proper preload and gear pattern. If the side adjusters are set correctly and the axles still have a lot of play then you probably have worn parts inside the carrier in which case it's time for a rebuild. Are you sure it's in the diff and not a u-joint?
Nate Wolfe
65 corsa 180

66vairguy
Posts: 2058
Joined: Tue Dec 21, 2010 3:44 pm

Re: 65 differential

Post by 66vairguy »

Beginning with the 1965 models the yokes at the differential were bolted in. They did not slide in and out like the EM cars. This change allowed the half shaft to act as the upper control link, like the 1963 and later Corvettes. On the optional POSI differential there will be NO play on one side. On an open differential if you jack up the car it's not unusual to have up to 3/4" of movement if you rock the tire/wheel by grabbing it at the top and bottom on both sides. The general consensus is up to 3/4" (at the top of the wheel) movement is acceptable. Seems like a lot, yet Corvairs handle fine. I've seen folks do some wacky stuff trying to get the "play" out and typically it ends up causing expensive problems.

Now I'm not saying your differential is fine, but the play does not indicate a problem since it existed in the new and in rebuilt differentials (as long as it is not excessive and the u-joints are good). If the differential is quiet and the lube is clean, then I would not worry. If the wheel play is excessive or there are noises, then it's time to dismantle and inspect the differential. Note the side bearings typically wear little, it's the ring and pinion shaft bearings that wear faster and when they fail things usually get broken.

A fellow in our club rebuilds transaxles and as he likes to say "The number one cause of transaxle problems are caused by old worn out lubricant that was never changed". A lubrication expert on the other forum suggests changed the gear oil every 30,000 miles. Use GL-4 80W90. Brad Penn makes it (now called Penn Grade). If you have a PG transaxle you can use GL-5 lube, but NOT in a manual transmission transaxle.

joelsplace
Posts: 931
Joined: Wed Oct 13, 2010 12:51 pm
Location: Northlake, TX

Re: 65 differential

Post by joelsplace »

I've never seen one with 3/4" of play but a disturbing amount is normal.
I was looking in my Chevy van GM service manual the other day and it says to change the differential oil every 15,000 miles and more often if towing.
I change mine with the oil change in my manual transmission Corvairs.
114 Corvairs, 5 Ultravans and counting
Northlake, TX

66vairguy
Posts: 2058
Joined: Tue Dec 21, 2010 3:44 pm

Re: 65 differential

Post by 66vairguy »

I checked my old notes on my one car - new lower control arm bushings, rebuilt differential, rebuilt axles (new bearings).

Just me, but if the top of the tire "tip" test is more than 1/4" I look for problems. Usually it's the lower link bushings or U joints causing excess play. When wheel bearing get bad you usually hear them!! If the wheel rotates quietly they are fine (until they aren't). BTW not sure where you are located, but use a Corvair shop to rebuild axle hubs if needed. Done right they will go 100K miles! I recommend Steve Goodman at Rear Engine Specialist in Colorado.

My notes on my 66 say the "tip" on psg. side was 3/32" in and out. The drv. side was 1/8" in and out. Keep in mind this is a car that has components as good as you can get to being like new.

Some basic geometry - (use the lower link as the pivot reference) indicates your worst case 0.050" in and out at the hub would wold result in the top of the tire moving about 0.160" or a little more than 5/32". Well within the 1/4" limit I use (Yes the consensus say up to 3/4" is fine, but like Joel I would be not be comfortable with that much play).

If your "classic car" inspection shop thinks your 0.050 travel at the hub is an issue, then ask them for a specific reason. Maybe they think it is the rear wheel bearings. Show them it's the half shaft moving in and out and normal. Remember the Corvair drive train is unlike your typical "classic American car". I've seen a number of botched Corvair repairs done by "old or classic car shops".

Good luck and maybe you should find another "inspection shop".

Rodders7762
Posts: 8
Joined: Sun Mar 11, 2018 10:04 pm

Re: 65 differential

Post by Rodders7762 »

Thanks for the replies. I’m guessing (after extensive search) that their is no actual tolerance figure given by manufacturer? Really don’t want to have to drop engine and rebuild it. I replaced all bushings and re did bearings it’s definitely the yolk moving inwards to the dif where the play exists.

joelsplace
Posts: 931
Joined: Wed Oct 13, 2010 12:51 pm
Location: Northlake, TX

Re: 65 differential

Post by joelsplace »

Rebuilding the differential probably won't change anything unless you have custom thickness nuts made to take out the play.
114 Corvairs, 5 Ultravans and counting
Northlake, TX

User avatar
bbodie52
Corvair of the Month
Corvair of the Month
Posts: 9466
Joined: Mon Aug 06, 2012 12:33 pm
Location: Lake Chatuge Hayesville, NC
Contact:

Re: 65 differential

Post by bbodie52 »

The attached documents may be helpful...

:wrench:
Attachments
1965 Corvair Chassis Shop Manual - SECTION 4 - REAR AXLE AND REAR SUSPENSION.pdf
1965 Corvair Chassis Shop Manual - SECTION 4 - REAR AXLE AND REAR SUSPENSION
(10.42 MiB) Downloaded 9 times
Overhauling the Corvair Differential - Technical Guide.pdf
Overhauling the Corvair Differential - Technical Guide
(1.28 MiB) Downloaded 8 times
Overhauling the Corvair Differential Carrier.pdf
Overhauling the Corvair Differential Carrier
(2.11 MiB) Downloaded 7 times
Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible

66vairguy
Posts: 2058
Joined: Tue Dec 21, 2010 3:44 pm

Re: 65 differential

Post by 66vairguy »

If you already replaced the lower control arm bushings then I doubt rebuilding the differential will improve the "play". As I stated before, your movement is not excessive. I've seen folks run far worse. The fact Chevrolet never specified a tolerance suggests it's not an issue. The only way to eliminate play would compromise the design and as I said before -- it usually ends up causing an expensive failure of the differential.

nirvairna
Posts: 13
Joined: Tue Jun 25, 2019 6:27 pm

Re: 65 differential

Post by nirvairna »

Rodders7762 - does the play at the wheel mean you failed your inspection and can't drive the car?

Rodders7762
Posts: 8
Joined: Sun Mar 11, 2018 10:04 pm

Re: 65 differential

Post by Rodders7762 »

Ok. Thanks again all. I will go back to the garage and talk with them and present all the info. So yes nirvairna I can’t drive the car till it passes inspection and one of the fail points was the play with the dif. Plus some minor brake things that I’m fixing.
They were looking to see if I could find a spec and as long as within that they would pass. I will chat with them and see what they say, if no spec for this then not sure how to proceed... will see what they say. Everything else on rear end has been replaced and so is only the dif movement. I will get a measurement after put back together and go from there. Might get the tolerance for the corvette ashas a similar set up... if that has a figure??

nirvairna
Posts: 13
Joined: Tue Jun 25, 2019 6:27 pm

Re: 65 differential

Post by nirvairna »

Good luck with finding a spec as if you're forced to do a repair it's going to be some work. At the least, it will be a diff swap with one that has very little play. You could also do as Joel suggests above, and decrease the play by welding and machining the retaining nuts. You could also buy the Clark's ultimate diff kit which can remove the end play.

Let us know how it turns out.

User avatar
azdave
Corvair of the Year
Corvair of the Year
Posts: 1889
Joined: Fri Dec 11, 2009 1:27 pm
Location: Phoenix, AZ

Re: 65 differential

Post by azdave »

Rodders7762 wrote:
Thu Jun 04, 2020 10:43 am
I can’t drive the car till it passes inspection and one of the fail points was the play with the dif.
If they are checking the play when the vehicle is lifted with tires hanging down and then grabbing the wheel top and bottom and rocking it, they will always see more play than most people expect. That play is normal and will not occur when the suspension is on the ground and loaded normally.

I can possibly shoot a video if that would help.
Dave W. from Gilbert, AZ
65 Corsa 140/4
66 Corsa 140/4
66 Corsa 140/4 w/factory A/C
66 Corsa 455 Toro V8
65 Monza Convertible 110/4
66 Monza Convertible 140/4
65 Monza 4DR 140/PG w/factory A/C
65 Monza 4DR EJ20T/5

User avatar
bbodie52
Corvair of the Month
Corvair of the Month
Posts: 9466
Joined: Mon Aug 06, 2012 12:33 pm
Location: Lake Chatuge Hayesville, NC
Contact:

Re: 65 differential

Post by bbodie52 »

Perhaps another late model Corvair owner in your area would be willing to have his Corvair examined by you and the inspecting mechanic for comparison purposes to see if there really is a problem with your car. It is possible that the mechanic's lack of knowledge or familiarity with the Corvair is making him assume that your car has a mechanical fault, when the fact may be that the unfamiliar suspension design behaves differently than the cars he is familiar with.
:dontknow:
Brad Bodie
Lake Chatuge, North Carolina
Image 1966 Corvair Corsa Convertible

User avatar
azdave
Corvair of the Year
Corvair of the Year
Posts: 1889
Joined: Fri Dec 11, 2009 1:27 pm
Location: Phoenix, AZ

Re: 65 differential

Post by azdave »

Two quick videos I made for you to show your inspector.




Dave W. from Gilbert, AZ
65 Corsa 140/4
66 Corsa 140/4
66 Corsa 140/4 w/factory A/C
66 Corsa 455 Toro V8
65 Monza Convertible 110/4
66 Monza Convertible 140/4
65 Monza 4DR 140/PG w/factory A/C
65 Monza 4DR EJ20T/5

joelsplace
Posts: 931
Joined: Wed Oct 13, 2010 12:51 pm
Location: Northlake, TX

Re: 65 differential

Post by joelsplace »

It may be an optical illusion but #2 looks like about half that play is in your u-joint.
114 Corvairs, 5 Ultravans and counting
Northlake, TX

Post Reply

Return to “Ask your Mechanical Questions here”