rear end decision

[SpeedingFirebird]

OK. Here is the long story.

I am saving my $ go get my motor work done. I couldn't decide how much to do on the motor, so I thought I would go 3.73s to see the power difference to decide if I wanted to bore .030 and get new pistons. I decided on an Eaton posi and 3.73 new. I don't like used parts. Well, it snowed and my car doesn't see salt so she is not going to make it to the shop (an hour away) until spring for the gear install, and I never ordered the parts.

The more I read on this board, the more I like the idea of getting discs in the rear. Swap out the entire rear-end, getting gears/discs/etc in one shot. Plus, I don't have to pay for the gear install.

Here is my dilema. I want to do the shocks/springs while the rear axle is out. Which means I will have to do the front as well because I am lowering the car. Oh, and might as well do the aluminum driveshaft while I am under there. By the time I spend all of that money, I am drained for the motor work, which is what I REALLY want done. Getting the gears done was a way to gauge how much money to drop into the motor.

I am of the opinion to get the motor done first, then worry about looks/handling/etc. I don't like the idea of used parts, but if I can do the install myself (instead of the gear swap), then I could save some cash? And I could do that now because the car can't leave the driveway.

What do you guys think? How hard is the axle swap really? I have not gone through the service manuals to see exactly what steps are needed, but I don't see it being that hard.

[shenanigans]

Its easy...

hard part is bleeding the brakes which is really not that hard, 2nd hard part is getting it lined up with the rear lcas.

later down the road to do the rear springs it will take like 20 min. top shock mounts are a pain but still very easy.

[SpeedingFirebird]

Eric,
Bleeding brakes is simple. I bought one of those vacs to do it one person, but I found it easier to just harass the wife instead.

What's the lcas - lower control arm support? You can assume I know jack about rear-ends. Given the weight, it this at least a two person job?

so you recommend the full axle swap?

I was searching around. Looks like an axle swap will only get me 3.42s at best. Is this correct?

Thanks

[ December 20, 2005, 01:08 PM: Message edited by: SpeedingFirebird ]

[ezrollin]

most people work on their suspension first, then do bolt-ons, then work on their engine last.

[SpeedingFirebird]

I want to autox the car, but my rear main leaks and my pumpkin leaks. hence putting the motor work first. If I pull the motor for the rear main, might as well toss in the cam and a set of P&P heads in prep for some boost. I certainly want the motor done before even touching the outside (I hate posers).

I know I need suspension mods for autox, but I doubt I can touch the track until the motor is yanked and fixed. Once I am on the track, I can figure out what suspension mods I need.

I have been trying to figure this puzzle out for a year now.

Every one has different intentions for their car. Thanks for your post though.

[1NotSoBadAssBird]

I say you do the gear swap and drop a limited slip differential if you dont already have it, used the left overs on engine work.

[zlexiss]

Well, do the motor first. You can't race if you're dropping fluids.

You can start racing while you save up for suspension mods. Yeah, you won't be the fastest or prettiest, but you'll learn a lot about your car and your driving. You'l understand why you want to do certain other mods (keeping your desired class in mind if that's important) instead of throwing money at the car.

[SpeedingFirebird]

Originally posted by zlexiss:
Well, do the motor first. You can't race if you're dropping fluids.

You can start racing while you save up for suspension mods. Yeah, you won't be the fastest or prettiest, but you'll learn a lot about your car and your driving. You'l understand why you want to do certain other mods (keeping your desired class in mind if that's important) instead of throwing money at the car.

Yeah, but I wanted to do the gears before the engine to determine the mods. [img]graemlins/stickpoke.gif[/img]

My thinking was maybe 3.73s would give me a significant punch on the low end that I wouldn't need/want to bore .030. That would save me a pile of dough on the engine rebuild.

See, this is why I wanted to discuss it with the people on this board. Figuring out the right order to do things is driving me NUTS!

[ December 20, 2005, 07:10 PM: Message edited by: SpeedingFirebird ]

[FuryCharger]

ok this is what I did.....Ive done everything to my car from simple intake and exhaust mods to complete rear axle and gear work to complete motor work....Typically, you will want to do the axle swap before you jump into motor work.....I went and did an axle swap because i wanted the disk brakes but to tell you the truth, the size of the rear rotors are so small they probably wont do any better job then the stock drums. the only thing is that the used axle mite come with a larger sway bar and it allows for a simple rear disk upgrade if you eventually decide to get larger rear disks. They are usually pretty cheap, i got mine for 250 with used gears and posi and its served me well for 2 years now. I did however swap the 3.42s out for 4.10s which I also recommend instead of 3,73s.

In regards to your motor work, think about it, its pretty pointless to do motor work and gain all that power without a form of posi in the rear to get the power to the ground. So I would do your rear axle upgrade first, whether it be just the gears and posi or a complete axle swap (also, its a pretty straight forward swap, took me 8 hours....rusted bolts were the hardest part), and then after the rear end i would go ahead and do the motor work if you have the money for it.

dont worry about the shocks, springs and driveshaft. they are all minor mods in comparison to the rear end and the motor and should probably be done after everything to compliment the major mods.

[shenanigans]

I have a mighty vac for the brakes too... buts its the biggest pain.

Putting the rear on people have told me its a 2 person job, but I have done it once by myself and pulled one out by myself before(had help outting it in, but I think I could have done it myself)

But I am a pretty strong guy. Some people cannot even move a 10-bolt by themselves.


LCA are lower control arms they are the 2 arms that attach to the frame and to the rear axle.

[shenanigans]

as for finding 3.73s... you might be able to do it but you will have to find someone with aftermarket gears. Highest gear ration was 3.42 form the factory.


I know it may not be the "performance kick"

but used rear goes for $100-200, I picked up a used 3.42 rear with 50k for $120 just recently.

a used lsd will cost that much, then the gears, then install, you are looking at like a $500-700 endevour depending on what you go with and buy, and that is before you get rear discs.

[SpeedingFirebird]

This is exactly the kind of discussion I was looking to have. Thanks for chiming in instead of saying "search". I've searched and still couldn't come to a conclusion.

It does look like I was on the right track at doing my mods in the right order though.

FC,
You make a GREAT point. I was thinking of the disc upgrade for looks only. I don't expect a huge win for discs in the back. Eric, jump in here if you think the discs will help that much in autox.

Seems to be a waste to do the axle swap and THEN do a gear change. So I'll have to keep my eyes out for an axle with the 3.73s already done. Seems to be the cheapest route. I like the idea of doing the swap myself just because I prefer to do my own work. Will any v8 axle from 93 - 97 work, or does it have to be off a z28/formula/TA?

True, 3.42s are better than my 3.08s, but I would still like the 3.73s. If I am going to spend the cash, I want to get the car exactly how I want it. I think 4.10s will take too much off my top end. My wife and I sometimes take the car on weekend trips, so I don't want to lose all my top end on the highway.

That mighty vac was a huge waste of money. A real POS if you ask me.

Good discussion. Keep the ideas coming. Until I actually spend the money, I will listen to all suggestions.

[zlexiss]

3.73's will bump you to a severe class (SM). In street prepared you can use the update/backdate to get to 3.42's since they were a stock option.

I'd do some races before choosing gears. Your region's site will help a lot - the shorter gearing might help or hurt depending on typical speeds you see by letting you stay in gear and avoid shifting.

I race on two pads. On the small pads I'd love shorter gears - I find myself either shifting a lot, bumping the rev limiter in first, or lugging in 2nd. shorter gears would let me hold second.

On the big pads I'm solidly in second the whole way unless there's a severe pivot. In this case, I might be redlining second a lot or have to shift to third with shorter gears, and my 3.23's are perfect.

So again, I'd say fix the leaks and start racing. When your driving gets better you'll be able to put priority on what you want/need to change.

[SpeedingFirebird]

Because of my wife's schedule, I was not able to make it to any of the local SCCA meetings this year. I am hoping to make it next year because her classes fall on a different night. The local group does most of their meets at the local airport usings cones. I think they have an annual trip to Pocono Raceway too. I imagine the cone track would be better with the 3.73s. I agree, it's hard to tell until I drive the track.

Fixing the leaks requires pulling the motor (rear main). When the motor is out, she'll be modded. Heads, headers, cam, and whatever else I can afford. Hence I wanted to do the gears first to see the power she put down. (See the catch-22 here?)

From what I understand, I am out of the street class because of my existing mods anyway. At least, that's what people on this board told me.

As a test, I could drive my bimmer for a race or two to try out the track. I hear that does bad things to my warranty though. But then I am not modding the FB until spring.

Thanks

[shenanigans]

Mighty vac is a godsend if you use it ot bleed your clutch...


I say look for a rear, if you find a 3.42 one for say $100-150 slap it in.


I understand not liking to pay for mods twice, I say just try it, then add the gears later. If you were to buy a used LSD for your car right now you are looking at like $100-200. So you will have made your money back with just hte LSD, on doing a v8 rear swap. Even more if you get the brakes.

it was a jump on 4 wheel disc brakes, even bigger when I put new rotors and hawk pads on.

But imo... if you can I' do a ls1 brake swap, if you can find it cheap.


Personally for a car that has a few road trips I think 3.42s will be nice and are much cheaper in the end.


But I am a cheapskate when it comes to mods....