Ok on my drive home tonight i noticed a whine on the overrun, got louder and louder, the started making a wailing noise on power as well tied ratcheting down a gear and got a load banging graunching noise, so i didnt do that again..

It's an 87 IROC-Z28 with 2.73 Posi gears...stock 305 tpi with auto up front

What's most likeley to have gone? pinion bearings? diff carrier?

I've read the FAQ's so I know what I'm looking for if i need to replace it..

I was also wondering if the time was right to upgrade, could I/Should I go for shorter gears 3.23 or similar? also i felt the LSD lockup wasn't great would often spin one wheel pulling hard out of junctions, is this something I can sort easily at the same time..

Thanks in advance..

pinion nut might of loosened up on ya. happened to me and the grinding is the pinion hitting the center piece. eventually it'll lock up. i'd upgrade to a posi, and shorter gears, but you can't do much better with your current series 2 housing.

from https://www.thirdgen.org/forums/tran...-10-bolts.html
Series II is 3.08 down, series III, 3.23 up. Steeper gears, say 3.73’s, can be swapped into a series II with gears designed for such a swap, or by purchasing a series III carrier.

Yea, you are probably looking at a total rebuild. Get a good brand of gears, a good installation kit and a Eaton Posi. You will be much happier with this.

Ad the prize goes to mathufman!

So today this happened..


yup pulled the cover and yep you were completely the pinion nut had come loose..

this is the result:





I'm planning on upgrading next year anyway so would just like to get this working again, can i just tighten it back up again? or can I just do the seals bearings/crush washer ect and run it like that?

are teeth missing on anything? if not or chipped you may be able to go easy on it for some more time, and a good cleaning out of all the metal shavings. i have worse pics.

no, nothing chipped or obviously worn, naturally some witness marks on the nose of the pinion, but the teeth look good..

Can I fit a new crush washer and seal without stripping the whole lot?

Luckily I have a big magnet on the back of the cover that seems to have got most of the swarf..

Take the nut off and clean the threads on the pinion shaft and in the nut (a new nut would be better). Use some red Locktite on the threads and torue the nut to about 125 to 150 foot pounds. This should get you by for a while.

and a new pinion seal too.

Great hopefully that'll get me through till I can afford a decent posi and some shorter gears..

i would have thought I'd need to replace the crush sleeve but saves me a whole 4 bucks if i dont!!

3.23 or 3.74??

It's never seen a dragstrip (it will but only for fun) but it's gets some serious street use, but also i would like it to still be able to cruise happily at 90 on the highway. til not sure if the .7's would be to short

What about the 3.42?

If you think that would make a good compromise street gear ratio then I'm sold, I defiantly want more grunt off the line, but I really dont want to make it a 1/4 wonder as it does a lot of high speed highway miles and this would annoy me and my wallet..

The 3.42 is a very popular gear with the 700R4 transmission. Put your numbers in this and see what you think. http://www.ringpinion.com/Calc_RPM.aspx

Someone on here has very kindly offered me an open diff with a 3.42 crown wheel and pinion, will i just be able to remove the cw of the open one and fit it to my posi? i'm not sure i fully understand the implications of the series 1 and 2 carriers..

Yes, but you will need a spacer between the carrier and the ring gear. The 2 series carrier (what you have now) has a thicker gear as opposed to the 3 series which is what you were offered. 2 series carriers are good for 3.08 and numerically lower gear sets. The 3 series carrier is good for 3.23 and numerically higher, but the ring gear is thinner.

http://www.nastyz28.com/forum/showthread.php?t=19773 Please read this and you will understand what you have to do to change the differential. I don't recommend ring gear spacers, especially in the 7.5 rear end. You need a 3 series differential to do this right.

7.5 differential without a spacer. Notice the machined area that centers the ring gear on the differential. This is a light press fit for the ring gear.

7.5 differential with a spacer. Notice that the machined area for the ring gear is almost completely covered by the spacer. There is nothing left to center the ring gear on the differential and the ring gear will be able to move around.

big gear head is absolutely right, the spacer is a bad idea. I've taken some of these rears apart only to find the ring gear loose on the carrier.

Nuts...

oh well guess i'm stuck with lame gear ratios untill i can find the cash for a new posi...

You'll be better off, sir

Have you been offered a complete 3.42 rear end or just the gear set? If you can get the copmplete rear end then go ahead and install it. You can add the posi later.

Been offered a complete diff assemby, but i don't want to loose the posi, and to be honest it's gonna be a year before i can spend out on an eaton, (not earning much at the mo as retraining)...

Wondering if i don't put the additive in with the new oil maybe the posi will lock up a bit better...

grrrr...

id swap it out for the open for now... i mean the posi really aint that great if you gotta baby it and worry about it falling apart on ya again... but i know what you mean a posi sure is nice lol

You might look into a Duragrip. It's a copy of the Eaton, but $350 instead of $440. I would still put in the 3.42 rear end and then upgrade later.

erm ok..

I'm not sure i like the concept of running with no posi, that means less sideways fun for sure, plus it spins up all the time in the wet as it it is, it'll be one wheel action all the way with an open diff! I can get a good used 3.08 gear set of ebay for $30 would this make any noticeable difference?

I've also seem these for sale cheap enough..though wrong for my axles as well I'd imagine
http://cgi.ebay.com/ebaymotors/10-bo...Q5fAccessories

Worth having or cheap junk?

I know i should just cough up and buy an eaton/duragrip, but i want to drive the car and enjoy it rather than laying it up untill i can buy the best which i do want..

Plus (probably a question for big gear head) what exactly is my POSI, it looks most like the eaton in the faq section , but it is not identical specifically the two little tags visible in the second biig photo that are at right angles to the clutch plates are noticeable different to all the others I've seen..

lol with it pieced back together how much sideways fun are you really gonna have? plus with that 273 i figured you could run 200 mph but couldnt launch if you had too lol j/k on that part

nah 136mph on the sat nav, flat out nothing more to come, launches terribly on the 2.73 it gets beaten of the line by pretty much everything with a 2.0 litre engine or bigger, it doesn't really start pulling hard untill 75mph...

and that was the sacriest 136 mph I've ever done as well! my daily drive Range Rover feels happier at 100+ than my camaro! I hope that will improve once i get a new/better steering box though....

I don't know what's for the best really, i cant throw money at it at the moment, but to be honest it's not a very fast car and it's got an auto box (which i don't much like) if i stop it going sideways I may as well drive my Mrs's Honda Accord turbo diesel, at least that's fast!
I just want to be able to enjoy it again untill I can afford to do it right when i get a decent job again next year... I've got a nice HO 350 with tiny hours on it I'm slowly building up for it, hopefully a manual box will come my way and then some bigger brakes it'll all come together in time, just hate seeing it jacked up on stands outside my workshop when i want to be driving it....

That differential on ebay is a Governor Lock. I like the way they took the picture from the other side so that you can't see the governor. These ebay people are looking to screw you whenever they can.

How about this. You get the 3.42 rear end and set it aside until you get the money for a better differential. Fix the rear end that's under the car now and drive it until you get the 3.42 rear end built the way you want it. Then do the swap. If you try putting in a set of 3.08 gears you will be wasting your time and money. You porbaboy won't notice any difference in the performance. You will also need to know how to set up the gears correctly and you will need an installation kit.

The differential that you have now is an Auburn. It's not the best. I quit selling them many years ago because of their failures. I was replacing them in 9 months because they were worn out and they were filling the rear ends with powdered metal sludge.