hey i was just reading a thread about how when you get a flat and you use your spare tire, the small one, it will ruin your posi, if you have it. why is this?

 

If the diameter of the wheel is not the same on both sides, one wheel will be turning faster than the other. Doubt it would wreck a posi in the short ammount of time and the low speeds you should be driving at with a spare like that.

 

I've seen this and repaired/replaced posi carriers for this exact reason. Depends on what type of 'posi' your talking about. The Eaton locking carrier will have bad clutch chatter and locking and unlocking of the rear wheels at low speeds. Not to mention governor and block damage as well as clutch wear. Clutch type differentials will only take about 30 miles of highway driving to wear out the clutch packs in the posi unit. The distance will be shorter with clutches that are already worn. With the diameter of the doughnut spare being so different than a standard tire, the clutch packs would be constantly slipping and wearing overheating then glazing. The smaller doughnut spare spins much faster than a standard tire causing the pinion shaft gears to constantly be spinning inside the carrier and having constant motion of the side gears. The best thing to do is if you have a flat on the rear axle. Remove a tire from the front and put it on the rear and place the doughnut on the front.

Jay

 

wow never thought about that before.....
im ditching my donut and putting my amp and cap in there

 

i dont even have a spare tire, thats the first thing i took out

 

The infaltable spare should be the same diameter as the 245/50/16 tires, so no problem.

 

i was going to say just take the frint and put it at the back! good call! what are you guys without spares going to do if you get a flat?? get it towed?

 

hellz yea z28, thats what i got AAA for

 

how much does that cost?? 20 bucks a month or what

 

weeeeee, though i'll probably still swap around and put it on front only.

 

yeah switching tires from front to back is great, but what do you do if you have the front/rear mount only tires. Like on my IROC, I guess you are screwed, no matter how you look at it then. I guess i shouldn't be surprised, I always seem to have luck like that anyway. Good to know though, and good thing i have triple A.

 

Those front/rear iroc wheels only have a small offest differance, Wont make that much of a differance.

 

Posi equipped car should have come with the inflatable spare anyway. Owners of cars later retrofitted with posi rears should look into finding such a tire.

 

As i have, put I'll just do the front/rear swap.

 

Fronts are fine on the rear, its rears on front that dont fly, in that case you'd be putting the spare on the front anyway.

 

What a pain in the butt when you only have one jack...

 

What a pain in the butt when you only have one jack...

Unless you have SFCs and can jack from the center of gravity. It's niiiiice.

 

SFC's indeed

 

if i counted the bolts on the differential cover, what does that tell me. someone told me and i cant rembmer.. what whats the diff between a 10 bolt and a 12 bolt.

 

LMAO dude, sorry I am laughin at you but I couldnt help it with the title of your ad. Its wicked funny... spare tire = KABOOM... LMAO

Peace,

Tom :lala:

 

What makes a 10 bolt a 10 bolt is the number of bolts that hold the ring gear to the carrier. In many cases, the same number of bolts that hold the ring gear to the carrier are the same number of bolts that hold the differential cover on the housing. But this is not the case in EVERY rear axle. For 1 example, I did come across one rear axle that was a 9 bolt ring gear with a 10 bolt cover. {No it didnt have just 1 bolt fall out} The carrier itself was a lot narrower than a standard auburn posi. I was told later on that carrier was made in Austrailia for the 10 bolt axle for the export models, or so I was told. So the best way to identify a rear axle is to count the number of ring gear bolts. But it is possible in general to identify what type of axle by the shape of the rear end cover and number of bolts.

Jay

 

well i have posi on my car, so if i had 10 bolts, for example. thats good. but if i had 12, thats better?

 

Sorry, its the number of bolts that hold the cover to the housing, there are several types of 12 and 10 bolts, so they arent all the same, but its the housing bolts that are the reference...

 

sorry Jay4Speed was right.

BTW, what exactly would you call the 10 bolt Olds rear end with the 12 bolt cover?

-Schultzy

 

Like I stated before, you can use the number of cover bolts method as a general way to identify the axle, but its not entirely accurate in every case. To be entirely accurate you have to count the ring gear bolts when ordering a new gear set. The number of cover bolts is more important to determine that you have the correct cover gasket and also the way that 'some' parts houses identify a rear axle. But when your ordering a ring gear you need to be certain of the number of gear bolts. And again, in many situations, the number of ring gear bolts are the same number that is in the cover. But not in every situation.

I can submit some another examples;

Corvette Dana model 44 I.C.A. independant rear axle has 12 bolts holding the cover on and only 10 bolts holding the ring gear to the carrier. Just try to order a Dana 44 3.70 posi carrier for a 12 bolt gear in a '75 Vette. Just wont happen.

Or perhaps a Saginaw 9.5 Inch HD rear axle. 14 bolts in the cover and 12 in the ring gear.

Or a Saginaw 10.5 Inch HD rear axle. Also, 14 bolts in the cover and 12 in the gear.

Or perhaps a Borg-Warner Model 78 with 9 bolts in the cover and 8 in the ring gear.

Most ring and pinion companies will identify wich type of axle by the shape of the cover gasket and number of bolts. This is also the way we identify which model axle to order parts for at the dealership as several different models of a '10 bolt' can exist in the same model platform. Most parts houses dont deal with number of ring gear bolts for identification. But if your not buying form a major company, GM, or parts house and you need to identify what gear / carrier you have the number of ring gear bolts in more important and accurate. Especially if the component is loose from the vehicle. Such as in a situation of buying an aftermarket Posi for a origional 'open' differential.

So to answer the question, both methods are correct but one is more accurate and resolves confusion when your trying to order replacment parts. Count the ring gear bolts, the cover bolts, and the shape of the cover gasket when ordering.

Jay

 

ok, if i take the cover off with grease and **** pour all over me?? because i really want to take a look inside. i guess if i do that ill need a new gasket. or maybe ill throw on a chrome cover!

 

Last I checked we were referring to GM rears, now your gonna go look in any magazine, at the GM rears, and the 7.5 8.5 10 bolts wow have 10 bolts on the cover, the austrailian rear in our car is referred to as a NINE bolt, yet going by your statement its an 8 bolt, sounds like we should stick to cover bolts when referring to them, and ring gear diameters when ordering gears.

 

Hmmm... who to beleive the ASE/GM master technician... or the theoretical moderator of TGO??... what a quandary!!

 

Seems when it comes to GM what I said applies, thats referred to as a NINE bolt, check your cover housing bolts and if you are ordering gears, measure the ring gear diameter, theres quite a few 10 bolts with both 10 in the cover and ring gear, yet they each have a different ring gear diameter, I stand by my previous statements, ASE tech or not.

 

ok im going to put this plain and simple cause im sort of a newb to car ****. a 10 bolt rear end, will put out more power then a 8.

True or False?


im just curious

 

Your rule does not hold true for GM rears though, and if you have had any experience with anything but 80s on up cars you'd know it. As someone pointed out earlier the 10 bolt olds rear.. If you're ever shopping for a 12 bolt for a chevelle look out.. some of the cutlass's and i think buicks too came with rear ends that have 12 bolt covers.. In fact, i beleive, the housing is the same as a regular 12 bolt.. BUT inside is the same little 8.5"? 10 bolt carrier and gears that are used in the 10 bolt rear of the same vintage. If you buy one of these rears you just got ripped. Theyre no stronger than the weakest link, which is the carrier and gears! This is the classic case of why not to go by the bolt #s on the rear end housing.

Now if you said that on 3d gen cars you can just count the # of bolts on the cover, than you would have been correct. It's just too general of a rule. The actual classic rule that you'll find on most car sites is to count the ring gear bolts to be sure.

As far as only 8 bolts on the b/w 9 bolt.. that i'm not sure about.. Just had one apart a few weeks ago too, but didnt count the bolts on either part. Would be par for the course, if the aussies made the exception to the rule.

 

ok.. um.. maybe im not making myself. completely, clear...

 

Can't tell you for sure which rear end will put more power to the ground.. Usually the stronger the rear the less efficient it is. For example a 9" ford is less efficient, but stronger than a 12 bolt gm. There are alot of different variables. The main ones are pinion placement and the shape of the teeth on the gears. The further out on the ring the pinion is the more leverage it'll have, and thus be more efficient. This is where the 9" ford is disadvantaged.

How this applies to 3d gens I dont know. Would be nice to see a dyno comparison between like cars.. Or even the same car after a rear swap.

 

84Z, that's the same solution Hot Rod gave when they had this info in their magazine 4 or 5 years ago. It just sucks if you're like me, and have larger tires on the rear. That's when the fix-a-flat comes in handy.

Do you have the original posi in your '84? It's actually an Eaton Gov-Lock locker, and they're pretty prone to failure. A governor in the center swings open to lock onto spider gears to activate the locker. The governor actually chips the spider gears! I swapped a 3.73/posi (locker)/disc axle under my '86 2.8, the axle came from an '84 Trans Am, engine code G, with a manual trans. And sure enough, my 2.8 blew up the locker. So I'm back on a junkyard's 1987 2.8l axle for the time being. (sigh)

 

im actually not sure. did it come stock with posi?? i dont think its stock, is there a way to tell?

 

Do you have engine code "G"? (8th digit of VIN)
Do you have a manual transmission?

If so, your posi is the Eaton gov-lock locker, and it came stock. 'Course, someone might've replaced it with another one before you bought the car, and the only way to tell that would be to drop the rear cover and see what differential you have.

 

if i take off the cover, grease and shti wont go all over me will it?? ill just probably need a new gasket? I dont even know really what i would be looking for unless someone can tell me exactly.. or refer me to a book or website

 

Well, looking up the vin is the easiest... do you ahve engine code "G" and a manual trans and rear disc brakes? (if you have rear discs and they don't work, you should bring your car to a GM dealer and have them check your VIN to see if the famous 82-88 rear disc recall was performed on your car. If it wasn't, you get it done for free- if you have a manual trans.)

There's also an axle code stamped on the FRONT of the passenger side axle tube. The code is in the center of the tube, and faces forward. You'll have to wire brush the area to see it. I've found it also helps if you wet your finger and rub it over the numbers. Axle codes are a long sequence of #s, but the first three digits are what counts. And again, you'd need to know the axle code to look it up, and, there's no guarantee that someone didn't change the insides around before you bought the car.