Will, contact me about the custom gears. We just happen to live right down the road (New Orleans) from the best gear grinder in the country (Prager) and a good friend of mine has offered to grind some new gears for the Fiero at pretty much cost. The more the cheaper, and we should probably let them take a crack at this. If you have the new parts we could send them to Prager for a quote. They build all of our large custom gears and service our gear boxes.

I know first hand that they would do a quality job.

I have all the parts. I have most of the guts of an NVG-T550 sitting on my counter top, much to the chagrin of my roommate.

------------------
'87 Fiero GT: Northstar, Getrag, TGP wheels, rear sway bar, rod end links, bushings, etc.
'90 Pontiac 6000 SE AWD: Leaking ABS unit fixed, load levelling rear suspension fixed, still slow

So far on the list we have:

For 3.0 1st gear:
Me
wcapman
Slammed Fiero
bushroot

Maybes:
87gt5speed
86 FIERO GT
Nashco

0.63 5th gear:
Me?
Nashco
bushroot

Anyone else?
In order to get price quotes for production, we need to know how many pieces to quote.
As it stands now, we have 4-7 1st gear sets and 3-4 5th gear sets.

Now, do those of you who want the 3.0 1st want the WIDER 1st gear as well? That would require slight machining of the 1-2 shift fork, which I can do for some nominal additional cost. I, for one will go for the wider 1st gear, just because. I urge the rest of you to do that as well.

------------------
'87 Fiero GT: Northstar, Getrag, TGP wheels, rear sway bar, rod end links, bushings, etc.
'90 Pontiac 6000 SE AWD: Leaking ABS unit fixed, load levelling rear suspension fixed, still slow

quote Originally posted by Will: Now, do those of you who want the 3.0 1st want the WIDER 1st gear as well? That would require slight machining of the 1-2 shift fork, which I can do for some nominal additional cost. I, for one will go for the wider 1st gear, just because. I urge the rest of you to do that as well.

My "maybe" is highly price dependent, and at 2 grand it's never going to happen. With this in mind, the extra cost of modifying the 1-2 shift fork and using a wider first (unless the cost is almost negligible) would deter me from purchasing. I really don't see breaking 1st gear being an issue if the proper material and heat treat is used. The first gear is a "would be nice" thing for me, but not nearly as much "gotta have it" as fifth gear.

I'll go out on a limb and say that I would purchase an upgraded gearset for $500 max first gear parts(widened or not), a little more for fifth gear parts. Perhaps in a year when I'm graduated and my school debt is gone, I would pay more, but at this point that's the highest I could commit to. You get under that radar and I'm in, assuming the parts are as strong or stronger than the current Getrag gears.

Bryce
88 GT

[This message has been edited by Nashco (edited 12-16-2003).]

Put me down for a mabey on the wide 3.0 & 0.63.
Thanks
Steve

hello Will, Im running a 3.4 dohc with the getrag 5spd. Id have to leave it up to you on what to use for gears, to be honest Im happy with the combo now. If you say it would help Im in. My best time is 11.7@117mph and it runs 2300rpm at 70mph now. Thanks Norm at www.normsfiberglass.com

Damn Will, you dont know how to take a break, do you?

I dont have a getrag but this makes some serious sense. Its odd the SBC guys arent all over this.

Let me know when you finish the 84. Id be interested in purchasing a Fiero modified by Will.

quote I'll probably put the Q4 back together with MG2 gearing, drop it on an '88 cradle, and install it in an '84 I've had out back for a while. Maybe then I'll be able to sell it and get it out of my yard.

I guess you're running a turbo to run like that. Are you running the 282 or 284 Getrag (Regular Getrag or the transmission that came with the engine)?
The gears I'm going to have cut will only work for you if you have the 282.

I've heard anecdotal evidence of turbo setups liking taller gears... they give the system something to load against and build boost faster. ANY engine will benefit from closer gear spacing. Do you have a lot of wheel spin when you launch? What's your best 60'?

If you launch at low RPM to avoid excessive wheelspin, then a taller gear will let you launch at a higher RPM, but will be harder on the clutch.

quote Nashco: With this in mind, the extra cost of modifying the 1-2 shift fork and using a wider first (unless the cost is almost negligible) would deter me from purchasing. I really don't see breaking 1st gear being an issue if the proper material and heat treat is used.

The cost of modifying the shift fork will be something on the order of $50 or less. It's really not much of a modification, just a little facing down to clear the new gear teeth.

I look at the idea of widening first more along the lines of "anything we can do to strengthen it when we're putting 150-200% of its design torque through it"

Another thing I'm looking into is adapting a Quaife diff for the Isuzu to the Getrag. I'm going to do some serious CMMing next week, but it looks possible, provided the Quaife has a significantly thicker ring gear mounting flange than the stock Isuzu diff, which is quite likely. The Getrag diff mounting flange is on the left side of the ring gear, while the Isuzu flange is on the right. I think facing the Isuzu flange back somewhat would allow mounting the Getrag ring gear to it. We'll see.

Unfortunately, Quaife no longer makes those diffs and has no plans to produce more. A freshly overhauled Getrag equipped with a Quaife and widened 1st gear should be able to take considerably more abuse in the clutch-dropping/burnout/HARD launch department than a freshly overhauled stock Getrag.

Not that ANY of us would EVER do that... but a certain margin of safety is nice

------------------
'87 Fiero GT: Northstar, Getrag, TGP wheels, rear sway bar, rod end links, bushings, etc.
'90 Pontiac 6000 SE AWD: Leaking ABS unit fixed, load levelling rear suspension fixed, still slow

I've been doing some interesting math...

The tooth load in any given gearset is input torque divided by the pitch diameter of the input gear. The pitch diameter of the input gear is the shaft center of the transmission (76mm) divided by 1+(gear ratio).
I set input torque to 1 Nm to make the final number come out as something easy to work with. Once I had tooth load, I divided by the limiting width (narrower gear) of that gearset. This gives me a tooth load (in Newtons) per inch of tooth width at 1 Nm input torque.
Here are those numbers:

code:

---

Gear  Ratio  Width  Specific Tooth Load (N per inch per Nm)
1st   3.50   0.735  80.56
2nd   2.05   0.648  61.93
3rd   1.38   0.668  46.88
4th   0.94   0.550  46.41
5th   0.72   0.568  39.84

---

As you can see, in stock form, 1st gear has the HIGHEST specific tooth loading of all the gears in the trans. Since 1st is already the most highly stressed, AND is subject to the heavy loads of hard launches, 1st gear is the most likely to break, in the event that one of the gears were to break.

Now look at this:

code:

---

Gear  Ratio  Width  Specific Tooth Load (N per inch per Nm)
1st   3.50   0.735  80.56
1st   3.00   0.735  71.61
1st   3.00   0.835  63.03
2nd   2.05   0.648  61.93

---

Just by going from 3.50 to 3.0 first gear, we drop the specific tooth loading from 80.56 to 71.61 (11% reduction). By widening first from 0.735 to 0.835 we reduce the specific tooth load further to 63.03, which is almost the same as the 2nd gear tooth load of 61.93. Widening the 3.0 first gives a further tooth load reduction of 12% from the stock width 3.0 1st. Overall, with the same alloy and heat treatment, the widened 3.0 1st gear will be 22% stronger than the stock 1st gear.
Wcapman is confident that his contact can make gears of superior alloy and heat treatment, for an even greater improvement in strength.

------------------
'87 Fiero GT: Northstar, Getrag, TGP wheels, rear sway bar, rod end links, bushings, etc.
'90 Pontiac 6000 SE AWD: Leaking ABS unit fixed, load levelling rear suspension fixed, still slow

[This message has been edited by Will (edited 12-19-2003).]

quote Originally posted by Will: the shaft has two splines, 3 bearing journals, and 3 integral gears,

and a partridge in a pair tree...

So are the people who signed up for a new 1st gear going to have to shell out the $3000 or so dollars to get that 1st gear? I assume by integral you mean the gear is part of the shaft (I know 1st and reverse on the 4-speed are part of the input shaft).

I think the idea of the modified 3.0 + wider first gear and a over-over drive 5th is great, but price does become an issue. Wondering if you (Will) have considered building Getrags with the new gears and selling them as complete units?

Thanks for making this an information-packed thread.

-Tim

quote Originally posted by Slammed Fiero: You know Im in!! Bump! JM THE SBC PUNISHER. VIN9 , 288 Cams, commander 950 and Direct port in progress!!..

Not to hijack yet another fabulous thread by Will but exsqueeze me did you say direct port injected SBC?!? Holy Horsepower Batman you're kid'n right?

Will, good thread and excellent find! Do you use the percocets to give your brain a rest?

quote Originally posted by normsf: hello Will, Im running a 3.4 dohc with the getrag 5spd. Id have to leave it up to you on what to use for gears, to be honest Im happy with the combo now. If you say it would help Im in. My best time is 11.7@117mph and it runs 2300rpm at 70mph now. Thanks Norm at www.normsfiberglass.com

11.7@117mph!!! That's insane for a 3.4 DOHC 5spd Fiero. Is it Turbo charged or something. Im sorry but there is no way a 3.4DOHC can run a 11.7 without some serious modifications. I think the 3.4 DOHC guys are seeing high 13's with their motors. Please fill us in.

-Amir

------------------

Maroon 1987 GT 5 spd: 2.8L
Ferrari Red 1988 Formula 5 spd: 3800 Series II Supercharged In & Running.....
Need any parts? Got 2 parts cars:
86GT 4spd
87 Coupe 4cyl

My Website: http://www.members.cox.net/rare88/

One option may be to make a new ring gear for the diferential. The IMSA race people take a Getrag and use a larger ring gear to get a lower final ratio. They are in the 4.30 range I believe. They weld the cases and then remachine the bores to move the differential away from the intermediate shaft for the larger diameter ring gear that has more teeth. This allows them to use the stock intermediate shaft. If one could come up with a ring gear with less teeth this could work.

That would be interesting for the Isuzuu trans, if that's even the same trans as used in Fieros.

Increasing the shaft center distance from the output shaft to the axle isn't practical for anyone but a race team. It also interferes with the use of street accessories like the VSS. Nice thinking, though. I'me sure there's a lot to transmission durability that the race team knows that would help us here... how much of that is doable on a budget I don't know...

I have an example of the 3.94 FD for the Getrag. It should go quite nicely with the 3.0 1st gear.

------------------
'87 Fiero GT: Northstar, Getrag, TGP wheels, rear sway bar, rod end links, bushings, etc.
'90 Pontiac 6000 SE AWD: Leaking ABS unit fixed, load levelling rear suspension fixed, still slow

This hasn't fallen off the radar. Wcapman and I are still looking into it. We dropped the parts off at Prager in N'awlins for them to look at day before yesterday. Not looking easy right now...

Here's an email from him:

quote Not such good news. Steve doesn't think they will be able to make this gear at anything like reasonable. The gear ratio that you are proposing does not leave enough root to make a strong enough gear. The problem is pinning it to the existing shaft. The material of the shaft does not work very well, so cutting or changing the shaft would be difficult, and require grinding, rather than tooling. To make a whole new shaft would require production equipment that Prager doesn't have. The cost of procurring those tools would make this prohibitive unless we did 1000 parts. Steve pointed out that the end splines are cut close to the shaft, which requires specialized production tooling. My ideas of welding up the shaft would have worked if the ground surfaces weren't direct bearing races. That makes the shaft almost impossible to modify. So, it looks like 1st gear changes are out. Tonight I'll run back over to Slidell to pick up the clusters from Steve's house. We'll look into changing the 5th gears to a taller (lower) ratio. I'm not sure if it's worth the effort to change just 5th. Maybe. Comments? Disappointments?

------------------
'87 Fiero GT: Northstar, Getrag, TGP wheels, rear sway bar, rod end links, bushings, etc.
'90 Pontiac 6000 SE AWD: Leaking ABS unit fixed, load levelling rear suspension fixed, still slow

It's certainly disappointing to hear about 1st gear manufacturing difficulties. Would have been nice to see it work out a lot more smoothly.

quote Originally posted by Will: I've been doing some interesting math... The tooth load in any given gearset is input torque divided by the pitch diameter of the input gear. The pitch diameter of the input gear is the shaft center of the transmission (76mm) divided by 1+(gear ratio).

I cannot get the math to work out. I've been trying to punch in these numbers just out of curiosity from the Muncie 4-speed for comparison. Maybe someone else will have better luck.

1st gear ratio 3.53
1st gear width .80 inches.

2nd gear ratio 1.95
2nd gear width .60 inches.

The distance between shaft centers is about 75mm.

Anyone want to post results??

The brain trust on this Forum is awesome!

This thread belongs in "Technical" (not complaining), because it is a fine example of well researched, thought out and useful technical data. Many thanks.

A friend and I are looking to do a Northstar with stick shift. We have a Getrag that came with the engine (and all the stuff to make it work), but I don't know if it will hold up, and it sounds like the gear ratio isn't that swift. I have some 4 speeds laying around, and an 88 coupe with Isuzu that may be the platform on which I do the swap. Maybe I should just use the Isuzu? I might need to look into that special gear deal you have going, so keep me in mind.

quote Originally posted by TimGully: It's certainly disappointing to hear about 1st gear manufacturing difficulties. Would have been nice to see it work out a lot more smoothly. I cannot get the math to work out. I've been trying to punch in these numbers just out of curiosity from the Muncie 4-speed for comparison. Maybe someone else will have better luck. 1st gear ratio 3.53 1st gear width .80 inches. 2nd gear ratio 1.95 2nd gear width .60 inches. The distance between shaft centers is about 75mm. Anyone want to post results??

I guess that the shaft sep is 76mm just like the Getrag and Isuzu.
76/(1+3.53) = 16.777mm (0.01677m) pitch radius on 1st input gear
1 Nm/16.777mm = 59.6 N load on each tooth of 1st gear with 1 Nm input torque
59.6/0.8 = 74.5 N/in Newtons per inch of tooth width at 1 Nm input torque. This number is what you use to compare the loading of different gears.

------------------
'87 Fiero GT: Northstar, Getrag, TGP wheels, rear sway bar, rod end links, bushings, etc.
'90 Pontiac 6000 SE AWD: Leaking ABS unit fixed, load levelling rear suspension fixed, still slow

OK, so the transmissions look like this then.

Getrag 5-speed

Gear--Ratio--Width--Specific Tooth Load (N per inch per Nm)
1st---3.50---0.735--80.56
2nd---2.05---0.648--61.93
3rd---1.38---0.668--46.88
4th---0.94---0.550--46.41
5th---0.72---0.568--39.84

Muncie 4-speed 3:32 final gears RPO code MY8

Gear--Ratio--Width--Tooth Load
1st---3.53----.80---74.5
2nd---1.95----.60---64.69
3rd---1.24----.60---49.12
4th----.73----.60---37.94

Muncie 4-speed 4:10 final gears RPO code M19

Gear--Ratio--Width--Tooth Load
1st---3.53----.80---74.5
2nd---1.95----.60---64.69
3rd---1.24----.60---49.12
4th---.81-----.60---39.69

Muncie 4-speed 3:65 final gears RPO code M17

Gear--Ratio--Width--Tooth load
1st---3.31----.80---70.89
2nd---1.95----.60---64.69
3rd---1.24----.60---49.12
4th---.81-----.60---39.69

[This message has been edited by TimGully (edited 01-11-2004).]

Yeah, basically. Since Tina has so many Isuzus apart right now, we should get her to measure the widths of the Isuzu gears.

If you wanted to be extra anal-retentive, you should say that tooth load is the force on the tooth for a given input torque, and specific tooth load is the force on the tooth per inch of width at a given input torque.

------------------
'87 Fiero GT: Northstar, Getrag, TGP wheels, rear sway bar, rod end links, bushings, etc.
'90 Pontiac 6000 SE AWD: Leaking ABS unit fixed, load levelling rear suspension fixed, still slow

quote Originally posted by Will: If you wanted to be extra anal-retentive, you should say that tooth load is the force on the tooth for a given input torque, and specific tooth load is the force on the tooth per inch of width at a given input torque.

and if you wanted to be extra-extra anal-retentive, I think that the specific tooth load formula we're using is actually for straight-cut gears. 45 Degree Helix gears would have slightly less loading due to that fact that helix gears are stronger and have more contact area than straight cut gears...

A thought I had today was that you could possibly take the 2nd gear (if it's part of the input shaft like the muncie is), grind the teeth off, possibly leaving enough material to hob a new 1st gear in it's place. Grind down 1st input gear & then spline the input shaft, and put a new 2nd gear in its place, because 2nd gear would possibly be large enough to have a splined gear made without falling apart.

This would certainly create a linkage problem, but that would all be external.

My other thought was since this whole gear idea is way too complicated (read $$$), just go with a 4t65e-hd auto instead...

Bummer. While reading, I was thinking I would have a set of extra gears to get hacked up if need be...until I read the price for multiple parts would be *COUGH*...nevermind that.

Thanks for the effort Will.

Bryce
88 GT