Performance Rear Differential???

[dgoodno]

:help :help

My mechanic and chief engineer, tonytgtr, posted a message titled "Q45 Performance Camshaft". Since then, I have had so much fun on the NICO site that he suggests that I post the next question even though I barely understand what he's talking about. I like driving the Q -- and the J, G and QX4, but not work on them. Well, that was true, but now I do have to do whatever is needed when I'm at the track!

So the question is, for track driving where acceleration out of the corners is most important, do I go with 3.80 or 4.08 gearing on the rear differential? What are the trade-offs? Are there other options?

[Mayhem_J30]

dgoodno,If you want to optimize average exit speed at a track it might all depend on which track you are at. If you're competing you should take the time to find out average initial exit speed (right after apex) of every turn on the course. Then figure out where that speed puts you in the power band. Based on that information you could decide wich gearing you would benefit from the most. Don't forget that turns before the longest stretches are the most important when it comes to exit speeds.

Where do you track at?

[90Q45blue]

dkill,

I think that the consensus was that it did help, but wasn't necessarily worth the money. Unless you need a new differential, it's just not something most members who use their Q's as daily drivers would consider. Now a project Q for racing is different. I agree that if money wasn't a huge issue, it would be a good mod.

Nick

[tonytgtr]

The reason he should put gears in his Q. Duaine says at summithe never gets out of second gear on the hole track. Tony

[AZhitman]

2nd gear - whole track?

Sounds like a perfect day to me.

BTW, it's not a $2K mod - Like I said before, buy a R200 out of a 90-96 non-turbo Z and swap out the stubaxles (Joe has them). Direct bolt-in beyond that.

Search for 4.08 on the site and there's TONS of good reading on the subject.

I will be doing the swap as soon as I can find a suitable donor rear and someone to swap the axles for me.

[dgoodno]

Dkill, I'm welded, no bolts. The cage has a bar going back into the trunk. I had already removed the backseat as I striped to reduce weight. I think I'm at 3800 right now. The biggest loss was I had to get rid of my heated seats and sound system.

Correction, 2nd gear at Summit except on the long straight. Can shift on the bridge straight, but leaves it awkward on the turn into the long straight.

[AZhitman]

d - What'd you do with the audio stuff?

[dgoodno]

:ylsuper I was a bad boy on the track. You are to stay in sync with your vehicle, wherer the sounds and feel of the car are more important then all else -- but I liked to crank up Faith Hill and go rocken down the track"":icesangel

I still have all. I probably won't get rid of the 10-banger CD, because I have three Q's and those things are hard to come by.

[EWT]

What are you using for brakes? Something bigger than stock I assume?

[HeavyDuty]

BTW, it's not a $2K mod - Like I said before, buy a R200 out of a 90-96 non-turbo Z and swap out the stubaxles (Joe has them). Direct bolt-in beyond that.

Search for 4.08 on the site and there's TONS of good reading on the subject.

I will be doing the swap as soon as I can find a suitable donor rear and someone to swap the axles for me.

dgoodno, it's a race car, and you need every bit of umph you can get to get a 3800lb pig moving. Too many examples of well set up cars with the 4.08 to think someone didn't do it for a reason. From a 1/4 mile standpoint, I'm still thinking 3.8's as a middle ground for my driver.

Hey AZ,

I just found a 90-96 NT Auto diff for the cost of jacking it up & harvesting it.

Ergo, since my pinion bearing (among other things) is going south, it looks like I'm going to have some spare parts in a couple of weeks. Interested?

I shouldn't speak before pricing the necessary rebuild parts, but I find it hard to believe it would cost even $1000 to completely go through one.

dkill, Bolt-in roll cage is an oxymoron. :pface

[AZhitman]

HD - Interested. Keep me posted.

[dgoodno]

EWT - I have AP 6-piston fronts bought from Stillen, however if you ask they will say the never sold APs for the Q. I think I'm one and only.

I get 3,600 miles on a set of pads.

I have stock on the rear where I get anywhere from 150 - 200 miles on the pads.

On my stock Q I get between 30 and 100 miles on the rears. It used to be better but when I warped the old calipers I got stock replacements that really suck.

It's hard to complain though, "I was driving my Q 125 mph hour and have to frequently brake to 45 -- and for some reason the brakes are not functioning properly! Can you fix them for me?" Somehow I don't think that would go over very well. Got both calipers replaced under warrenty! :icesangel

That was a couple years back and now I pretty much avoid the stock on the track. I'm just too damn aggressive for it. :rolleyes

[dgoodno]

I thought bolt it meant it wasnt welded into the frame, rather connected...

What it sounds like they have done is to have bolted in a welded cage. It will help but the integrity is questionable in a serious accident. Most bolted cages are not very tight. In an accident the bolts tear out.

My cage is part of the frame. As I had said earlier, as part of the cage I had a post stuck down through the trunk and I can lift the rear axle by jacking up the "cage"!:thinker

[HeavyDuty]

I thought bolt it meant it wasnt welded into the frame, rather connected... this is what i have been told and seen myself.. One can be removed without any cutting, one can't

There are bolt in "street" bars & I'm sure they aid somewhat, but the idea of a cage is twofold. Protect you in the event of inversion or intrusion from another object. And, take the responsibility of structural integrity away from the unibody structure. Drag racing, autocrossing, road racing, etc, twists the body. At minimum, the flex causes the car to handle drastically different, at worst, it will flex the body enough along stress points to crack the body, permanently making the car "not straight" anymore. Too late at that point to do any reinforcing.

Don't worry about it too much unless you're hooking up. If you're looking at a car that has a cage in it, check the log book for previous accidents and/or take it to a body shop with a good frame machine for critical measurements to insure it's not already twisted.

[dgoodno]

I don't understand how Mitch was able to assemble a fully welded cage into my Q. He did and it's damn tight. There is maybe a 1/3 inch between it and the skin. I truely marval at his artistry.

In a high speed roll over or crash the cage will protect me from being crushed, but it seems that it will also remove some absorbtion. In a high speed, I think having the safe zone may be more important.

The weak point then might be the seat. Many are not properly installed and can rip out on impact. Here too I think I am secure. The same person who installed the cage installed the seats -- with five-point harness.

As for the welded - bolted in cage. How fast of an impact are we expecting? In a secure crash I do think the bolts will tear out. What is it bolted to, the frame? If so, then the weakest point is the bolt itself. But what if they do rip out? I think you are still safer with it, then without.

Consider that you will be one of a few with any cage. Certainly it is better then none at all? And at lower impacts it should provide complete isolation from the external force.

dkill, what seats are in it. What seatbelts? Those may be the weakest points in a crash.

:ak47

HD, do you agree or am I missing something in the logic?

[dgoodno]

Ok, I will get someone to crawl around the car and take pictures. I should have thought of this before. Actually easier then me going though 20 hours of film to see if I have something here.

The car is FULL of parts that Tony took off the engine/exhaust/trans when these things were removed, but still should be able to get some shots.

As for the bolt on, I'm wondering if it's possible to increase the integity by welding it in place?

The size and strength tube used and it's shape I think are important. The fact stock seats remain MAY be an indication that the tubing is thin and the design made for convenience, not true utility.

I look forward to your pics and I'll try to get some taken and posted. The artist who did mine is Mitch Piper (sp) from northern Virginia. I recommend talking to him before you do anything with the cage.

[dgoodno]

I didn't find his name and number on the web, so call OGRacing 8009349112. They are located not too far from Mitch and I know that they know him. I ordered the seats from OG and had them delivered direct to his shop.

[dgoodno]

Got it and understand!:bearchug:bearchug:bearchug:bearchug:bearchug

[dgoodno]

I have added a new thread on the overheating problem on track -- and posted another picture.

[EWT]

EWT - I have AP 6-piston fronts bought from Stillen, however if you ask they will say the never sold APs for the Q. I think I'm one and only.

Cool. Did they make brackets for the calipers so they would bolt on?

I think the stock front calipers/rotors would last for about a corner and a half before serious fade set in. I've always wanted to take my Q45 out to the track, but never got around to it. I'm not going to the track once or twice a month like I once did, so I always end up taking the Supra now.

Eric

[dgoodno]

Good question. I don't remember as I had someone install them when I had suspension, air intake and exhaust modified. Seems that we had to do something on our end to make it work, but when I finally wore out the pads last year I spent considerable time screwing around with the calipers to figure out what to do -- and I didn't see anything that looked like it was Gerri rigged.

Tony, if you read this ask John. The work was done at the shop where he worked way back then.

[dgoodno]

Thanks everyone. :ylsuper

Looks like the consensus is, that for my vehicle which is a project car used on-track, that the 4.08 is useful.

My options are: 1) to get from Stillen, this being fast, but expensive. 2) Check with the club (BRM) to see if anything is available. 3) buy (from Joe) a R200 out of a 90-96 non-turbo 300zx and swap out the stubaxles [flanges are 5-bolt vs. 6-bolt].

I think that completely summarizes the suggestions. Let me know if I missed anything.

I have added a new thread, " Racing Q: Weight, wiring, gauges and fire suppression".

Duaine

[HeavyDuty]

Junkyard diff, rebuild as necessary, if necessary.

On the tubing on the cage deal, a plate can be welded underneath the floorpan and or above it to weld the cage to. In areas where there's a frame rail, it should be welded there.

I wouldn't ditch your cage, just weld it where it's bolted.

[dgoodno]

dkill, HD and I agree on this one, if the cage is solid otherwise, weld those bolt joints in. There is no reason to rip it out unless the integraty is otherwise not there.

My suggestion is to wait until you have the vehicle in hand. Take pictures, pictures, pictures. Also call Mitch and see if you can get an email address for him. Let's evaluate this sucker together. :icesangel