1998 Formula Firebird LS1/T56 - ESP build Options

[robz71lm7]

No chassis difference between the two. Pull down the headliner in a 4th gen sometime. The T top option was baked in.

Bull. This is an oft repeated myth. Look at the cross sectional area of the members connecting the A and B pillar.

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[Blainefab]

No chassis difference between the two. Pull down the headliner in a 4th gen sometime. The T top option was baked in.

Bull. This is an oft repeated myth. Look at the cross sectional area of the members connecting the A and B pillar.

Rob is correct - the sheet metal in the Ttop roof structure is thicker than the hardtop.

[Beach Cruiser]

I run the Z06 rears all the way around with 315 rubber. In the rear I needed a 5/16 spacer and in the front I used a 1/4" spacer with ARP studs. I also have the upper control arm camber bushings. Strano/Koni and Strano's bars. I'm using an Auborn Diff. My car is usually in the top 20 in our region. I'm VA State Champion two times in ESP.

[2MCHPWR]

I run the Z06 rears all the way around with 315 rubber. In the rear I needed a 5/16 spacer and in the front I used a 1/4" spacer with ARP studs. I also have the upper control arm camber bushings. Strano/Koni and Strano's bars. I'm using an Auborn Diff. My car is usually in the top 20 in our region. I'm VA State Champion two times in ESP.

do you use a watts link and aftermarket torque arm? if so, which ones? how much does your car weigh? Do you think you'd do well against the turbo buggies in STU?

[camarokid91]

I run 315 Hooisers for SCCA and 305/660 + 305/680 Pirelli's for club all on C5Z wheels.

(IMG:http://i.imgur.com/xLzcuf5.jpg)

(IMG:http://i.imgur.com/TX9OogV.jpg)

[dailydriver]

My previous region's ESP group went through most of the diffs, and the Eaton clutch diff is the one that holds up to 315 A6s on all 4 corners. The helicals and Auburn Racer's diff didn't last long. My car came with the "Zexel-Torsen" diff. It didn't work after 120,000 miles.

Has anyone actually rebuilt the Eaton CF clutch pack Posis with the stronger springs available (800# I believe?) to run autocross/open tracking/etc.??

Or would that make them even worse than a locker as far as being too 'spool-like' for corner exits/slow apexes/etc.????

[FlatBlack]

My previous region's ESP group went through most of the diffs, and the Eaton clutch diff is the one that holds up to 315 A6s on all 4 corners. The helicals and Auburn Racer's diff didn't last long. My car came with the "Zexel-Torsen" diff. It didn't work after 120,000 miles.

Has anyone actually rebuilt the Eaton CF clutch pack Posis with the stronger springs available (800# I believe?) to run autocross/open tracking/etc.??

Or would that make them even worse than a locker as far as being too 'spool-like' for corner exits/slow apexes/etc.????

Racer X Has a rebuild kit for his, he might be able to talk on that some.

[FlatBlack]

Track day at Harris Hill Road yesterday, someone grabbed this pic (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif)

(IMG:https://farm6.staticflickr.com/5601/15457100881_973ff832c1_k.jpg)

Car's working really well. Headers going in this week

[Smitty2919]

I'm interested in all this differential talk. I need to get on over the winter for next season.

Flatblack, what was your reason for going with the Eaton clutch pack vs Eaton TrueTrac or even the Auburn Race diff with their rebuild program? How is it working out for you?

I'm only running 275 V710's on stock 10 spoke ss wheels and try to autocross as much as possible with the car being a DD. I have horrible RH turn pass rear tire spinning issues and can't power out of turns.

I like the rebuildable clutch pack/spring idea vs Auburn/helical gear design only offering their rebuild program for the first 4 years after initial purchase.

[ReEntryRacer]

I like the rebuildable clutch pack/spring idea vs Auburn/helical gear design only offering their rebuild program for the first 4 years after initial purchase.

Just a correction... the auburn does not use the helical gears, that's Torsen. Auburn uses bronze cones/springs. And they will keep replacing the diff. forever as long as each one is within 4 years of the build date stamped on it. I'm on my 3rd in 10 years.

[Smitty2919]

Ahh yes brain fart. I meant it as the torsen helical gears and auburn cone gears are not serviceable.

In terms of wear, you may only use your car for racing only maybe once a month and have had 3 diffs in 10years. I will DD mine seeing 10k mi if that per year and autocross once a month during autocross season.

Do you think DD a diff with monthy autocross needing replaced once a year?

[ReEntryRacer]

Ahh yes brain fart. I meant it as the torsen helical gears and auburn cone gears are not serviceable.

In terms of wear, you may only use your car for racing only maybe once a month and have had 3 diffs in 10years. I will DD mine seeing 10k mi if that per year and autocross once a month during autocross season.

Do you think DD a diff with monthy autocross needing replaced once a year?

I have an '01 Firehawk with original Torsen and 60,000 miles. It still leaves two black strips out of every corner, only serviced once, and it gets driven HARD.
The racecar with the Auburn was built and used for mini-enduro races of 1 hour or more, on my home track with most corners as tight as any AX course, but with fast entries to most corners.
I gave up on the Torsen in the first season of racing as it just did the 'one tire fire' all the time. The Auburns have stood up and worked well. The first one I folllowed the instructions and added the lubricity additive they send in the box. Bad idea for a race car, its quiet, but it slips too much. I filled it without synthetic or additive (Red Line HD) and got all the bite I needed.

Only caution is that Auburn will ask you to prove (send pic) that you will use their Racer's Diff. in your race car. I assume that means it will not last as long in a DD due to the higher bias.

[Smitty2919]

I have an '01 Firehawk with original Torsen and 60,000 miles. It still leaves two black strips out of every corner, only serviced once, and it gets driven HARD.
The racecar with the Auburn was built and used for mini-enduro races of 1 hour or more, on my home track with most corners as tight as any AX course, but with fast entries to most corners.
I gave up on the Torsen in the first season of racing as it just did the 'one tire fire' all the time. The Auburns have stood up and worked well. The first one I folllowed the instructions and added the lubricity additive they send in the box. Bad idea for a race car, its quiet, but it slips too much. I filled it without synthetic or additive (Red Line HD) and got all the bite I needed.

Only caution is that Auburn will ask you to prove (send pic) that you will use their Racer's Diff. in your race car. I assume that means it will not last as long in a DD due to the higher bias.

I have heard from others about not adding in the additive to the Auburn Diffs. How do you prove a car is a "race car"? Put stickers all over it? lol Do they frown upon replacing the diff if you put it in a DD? lol

[dailydriver]

Only caution is that Auburn will ask you to prove (send pic) that you will use their Racer's Diff. in your race car. I assume that means it will not last as long in a DD due to the higher bias.

I know this is a very subjective question, being that they are such dissimilar diffs, but does the Auburn Racer's diff seem to be at least the equal, as far as bias goes, to the T2R, or not??

This question is open to others who may have had BOTH, if you have never used a T2R.

[Smitty2919]

I thought I came across something saying the T2R was higher bias than Auburn....but since the Torsen's have/had quality issues etc does it even matter? lol

I would call a vendor of both and ask. Strano comes to mind of knowing since I believe he ran a T2R and went to Auburn due to the T2R quality issues and Torsen's inability to acknowledge the issue.

This post has been edited by Smitty2919: Oct 13 2014, 08:49 PM

[FlatBlack]

I'm interested in all this differential talk. I need to get on over the winter for next season.

Flatblack, what was your reason for going with the Eaton clutch pack vs Eaton TrueTrac or even the Auburn Race diff with their rebuild program? How is it working out for you?

I'm only running 275 V710's on stock 10 spoke ss wheels and try to autocross as much as possible with the car being a DD. I have horrible RH turn pass rear tire spinning issues and can't power out of turns.

I like the rebuildable clutch pack/spring idea vs Auburn/helical gear design only offering their rebuild program for the first 4 years after initial purchase.

From the last page:

My previous region's ESP group went through most of the diffs, and the Eaton clutch diff is the one that holds up to 315 A6s on all 4 corners. The helicals and Auburn Racer's diff didn't last long. My car came with the "Zexel-Torsen" diff. It didn't work after 120,000 miles.

So I've only had the Eaton clutch type, but 3-4 guys using the same axle came to the conclusion that it worked the best. From what I gather, I'm going to need to rebuild even the Eaton every other year or so, but it seems to hold up the longest on Hoosiers.

No complaints with mine, I actually had the inside rear chirp pulling out of a parking space the other day, so it's still working for sure. It has probably 1000+ miles and 80+ autocross runs on it by now.

[dailydriver]

When everyone rebuilds their Eaton Posi, do they just replace the carbon clutchpack with the same, or do they switch over to the 'old school' steel clutchpacks??

I take it that NO ONE is running the 800 lb. springs in theirs, correct?

[FlatBlack]

Lots of winter upgrades happened.

Installed TSP 1 7/8" Longtubes and a 3" Off Road Y-Pipe. Currently still using the stock exhaust from the I-Pipe back, but plan to dump at the axle. Hopefully later this year.

Got the Strano 35mm hollow bar, ended up being 5# lighter than the 32mm solid bar I had been running, and should be much stiffer. Also took some weight out buy pulling the A/C compressor/lines, radio/speakers, and air pump box. Was about 50# total.

Last but not least, I picked up Dave Ogburn's CCWs. They are 17x12 (he also gave me the 11" outers) with 335s on the front, and 315s on the rear. Can't wait to try these steam rollers out at the College Station Annex for the Texas Tour (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif)

(IMG:http://i254.photobucket.com/albums/hh81/flatblack280/Mobile%20Uploads/CYMERA_20150307_091057.jpg)

This post has been edited by FlatBlack: Mar 20 2015, 03:16 PM

[Steve91T]

You've got the wider tires up front?

[FlatBlack]

You've got the wider tires up front?

Yes