FYI- Beware of GBox false claims -$$$ouch!

[umgang]

Just an fyi from sour experience.
They do not do good work, they do not stand behind their work.
If you want the story / history read below.
Otherwise, go somewhere else and let's put these guys back in the lawnmower business where they
belong.

Story:

Car is a 1975 911S with 3.6L M64 motor w/ OEM 915 trans..... GTS4 2nd pl Champion car..
The tranny had been built and strengthened by Jeff Gamroth/ Rothsport, Tualatin, OR in 2008 -
ran 3 seasons of racing / 35 + races when the third gear blew at Hastings.
Sent it to GBox for rebuild and a supposed stronger third gear.
$ 7700.00 later + removal and install got it back in, with a persistent leak.
Contacted them and they told me this is SOP for magnesium cased 915s; even though they
were made aware that it had a seepage and said they could take care of it.
Tranny blew third gear after 1 race and 1 enduro.
Their response: it's a race car we do not guarantee anything.
Then check this--> they offered to build me a a G50!! hahahaha
Man, what a racket. Charge race shop prices, and not have to stand behind it because
it is raced.
You've been warned.

Nic

[Joe Bob]

Never heard of them.....what brought you to them? Recommendations from others or were they close?

Might want to list their location and names of the staff that lightened your wallet. What was the reason that the box failed the first time? Was the cause and effect both corrected?

Was the faiure due to the IM bearing getting loose? If so, how was it fixed? Was it modified with a bearing retaining plate like the 930 box has stock?

[umgang]

Good thing you have not heard of them!
A shop in Kansas City did the work and sub-contracted to them.

The car has a 3.6L M64 motor which the 915 was never meant to handle.
But, Jeff Gamroth did a nice job of reinforcing the side case ala WEVO; put in a
bigger main shaft, ....The tranny lasted 4 years, 35 races+ etc...when a tooth in third gear
set broke. This is actually the weak point in all 3.6 conversions since third gear takes the most
torque and power.

Gbox claimed experience with this, committed to the work to put a stronger third gear and fix a persistent seepage from Gamroth rebuild. Got it back with a worse leak which i addressed and they ignored.
Tranny blew third gear in just a few months after rebuild after just 1 sprint race and 1 enduro.

This is a Metzger GT1 engine - 1997 M64/23.

Just want to clue folks in to put Gbox in the ' wannabee' column so no one else gets burned.
Amateurs need to learn somewhere/ somehow; but should also bear some of the cost of learning on others' expensive equipment.
It is more the unethical -care-less response that gets under my craw.

[Joe Bob]

BTDT my 2nd gear went when the shell ovaled in the IM plate.

Maybe it's time to get a G50?

Good luck.

[umgang]

Yeah_ it is a torsion bar car still and the G50 i would have to go to coilovers...
I've heard there is a shortened bell housing for G50 installs into t-bar cars.


Here is their info for everyone to forget:
GBox
5757 Arapahoe Ave C1 East
Boulder, CO 80303

Cobbed me for $ 7734.50 + removal and install at the KC shop.

[Matt Monson]

Gbox is owned by the former mechanic of Chris Fisher's infamous operation, PowerhausII. Stan, the owner and lead technician has several decades of Porsche transmission building experience. They are not a Guard Tramsmission authorized installer, so I can tell you that whatever aftermarket race gear they put in the box was probably not manufactured by me.

FYI, Chris Fisher is back in business, once again selling Albins gearsets under the business name of Vista Grande run out of somewhere in the San Francisco Bay Area.

I share this as neither anything for nor against Gbox but just for informational purposes for people trying to figure out who these people are and where they came from. The business has been around for half a dozen years since PHII went bankrupt, though they have tended to focus on the water cooled gearboxes and thus why many in this forum would not have heard of them.

Regards,

Matt Monson
Guard Transmission. Llc

[Mahler9th]

Very sorry to hear about your issues.

Gamroth does excellent work.

We have a number of guys (including myself) running 3.5 - 4 liter engines with race cars running 915 transmissions out here in NorCal. I have a bunch of parts from WEVO, and they have provided excellent technical support and service. I also have some gear sets from Guard Transmission, and they too have provided excellent technical support and service. Both Paul and Matt.

Lots of things can happen when 915's are used in high bhp applications, and there are some "must do's," and "nice to do's." Its great to work with folks like WEVO and Guard Transmission and we are lucky to have them still working with 915 stuff.

I have no experience with Gbox and I am not likely to use them for anything or recommend them.

[Dave 86 930 Fl]

Thanks for posting your experience.

[Deadeye]

I purchased a track car 3 years ago. The PO spent over $12K on a G-50 from G Box that was supposed to be built for track duty. New R&P, new short gears, bearings, synchros etc. After less than 2 years limited track use the "new" 8:32 R&P (with no manufacturers markings) ate the gearbox. We only managed to salvage a few gears the case. It was either an improperly shimmed R&P or poor quality parts.

[umgang]

Well fellas, it is a hard thing to write a post denigrating a vendor/ contractor.
In this case though, i see from the responses here, and all the other sites i posted on, that
the consensus is that Gbox is unfit to work on Porsches.
Hopefully this will keep others from getting taken by their dishonesty, and overall
lack of ability.
Thanks a lot for your honest appraisals and input.

Matt_ if i get to affording another rebuild i will be talking to you about the Guard 3rd gear set.

Nic

[911dean]

I've talked to a few shops about building a close ratio 915 box. All them use Guard and Wevo parts. Must be a reason.

[Matt Monson]

Umang,
May I ask a question that may be of assistance to others with a similar engine and gearbox configuration to yours? Can you tell us what ratios were used in your gearbox?

[Matt Monson]

I purchased a track car 3 years ago. The PO spent over $12K on a G-50 from G Box that was supposed to be built for track duty. New R&P, new short gears, bearings, synchros etc. After less than 2 years limited track use the "new" 8:32 R&P (with no manufacturers markings) ate the gearbox. We only managed to salvage a few gears the case. It was either an improperly shimmed R&P or poor quality parts.

Can you pm me more details on the gearbox and previous owner? I think I know what gearbox this is and there is more to this story.

[Steve@Rennsport]

Matt,

This one has stock gear ratios.

[Matt Monson]

Matt,



This one has stock gear ratios.

Got it. While I have nothing to gain by vindicating Gbox, I want people to carefully consider what I am going to post next.

It has been, and continues to be, common practice with many gearbox builders, many very reputable race shops, to take good used stock ratio NT 3rd gears out of street cars, and put them into a race box as part of a rebuild.

This practice has about equal odds as playing craps at Vegas when used with the commonly used 3.6l swaps and high strung built 3.2 and 3.4l engines being produced today. Regardless of mileage on the gear, the newest 915 used gears are more than 25 years old.

Whether Gbox used a "good used" gear or an all new replacement is not 100% clear here. If it was a used gear installed then I have to agree with their "that's racing" response on a certain level because that used gear is a giant unknown question mark.

If it was a brand new just manufactured aftermarket gear I would be looking for an autopsy. I cannot speak for how anyone else's handles these situations but while I openly state that everything I make is for motorsports use and carries no warranty expressed or implied, if there is a quick failure I want to get to the bottom of it.

Last year I had a European vintage rally team break one of my 3rd gears. The car had fewer than 100 stage miles on it when it broke. I immediately requested the gear for inspection.

Once I had the gear and could see the nature of the break I had some very specific questions for the team. What my inquiry revealed was that the gear broke when they landed a jump with the car in gear on full throttle. The wheels were spinning a lot faster than their "air" speed and when they landed the car the deceleration shattered the gear. Sorry, no warranty.

I didn't leave the customer swinging in the wind though. I sold them the replacement gear at my cost and strongly advised them to lift throttle while air borne going forward.

I manufacture a line of stock ratio 915 gears specifically for the pca stock letter class cars as well as the PRC 911Spec series cars. Jerry Woods/Rich Walton won't build one of those Spec race without installing both my replacement 2nd and 3rd gears at a minimum. $1700 of gears added onto the cost of building your racecar may sound expensive, but when you look at the cost of umgang's follow up repairs when there is a failure, that amount suddenly seems more like cheap insurance.

There was a time when there were a lot if nos 915 oem gears floating around. That stock is drying up and any of you building racers with stock ratios, especially at higher power levels than the original 3.2l engine produced, want to seriously consider how you prepare your gearbox. Our billet side cover and 1 piece bearing retaining plates are kind of no brainers. But if you can afford, at a minimum a new 3rd, and depending on where you race 2nd and/or 4th I would strongly recommend you consider it.

[Matt Monson]

One other thing to consider is also a regear. We very frequently see short ratio and close ratio gearing thrown around as if they are the same thing. They are not. By going with a taller than stock 3rd gear, you can introduce a gear that is stronger than stock.

A 3.6 has more torque than a stock 3.0 or 3.2l engine and can pull a taller gear. I think KTL has a gearbox like this in his car. What you do is start with 2nd and instead of the stock 1.78 or 1.83, you kick it up to a 1.68 or similar ratio. Now you can move your 3rd up to a 1.22 instead of the stock 1.26. Yes, you technically have less mechanical advantage in each gear than you had before, but not only do you have a marginally stronger gear, but you have improved your rpm drops. That improvement is what we are looking for in a close ratio gearbox.

I would have to look at an actual chart (Bill Verburg runs beautiful charts with thrust forces that display this well) to prove where the gains would be. But let's pick an arbitrary 90mph and say that while you have less mechanical advantage there than you had before because your engine is now more on the sweet spot and making more torque at that speed than it did with the original ratio, your power to the ground (thrust force or wheel torque) is now higher.

That is one of our primary goals when we regear. We want to increase power to the ground at given speed. Sometimes that happens with shorter ratios than stock, sometimes that happens with taller ratios than stock. What is consistent about it is that we do is by providing closer ratios than stock that make your upshifts put your engine closer to where it making the most power. That is how you get best acceleration.

[911dean]

Matt
Excellent post on using used gears and potential problems in doing so. Makes a lot of sense. It will help me justify buying 4 new gears. Keeping my engine in it's power band is why I want to regear.

Do your new gears for 915's use a better/stronger grade of steel than original equipment?

Thanks,
Dean

[Matt Monson]

Yes. Alloys and heat treating, as well as tooth profile technology has advanced substantially in the last 40 years since the 915 was first designed.

[Marc Bixen]

Great thread Matt.

[cstreit]

I would never EVER again put a 915 along with an engine making more than about 220 hp and expect it to hold up for long. You will end up learning expensive lessons if you try... particularly the mag cased version.

I learned this lesson, perhaps you recall the number of times I had to rebuild my 915 nic?

I wouldnt necessarily blame it on Gbox per se. If I were them I would have counseled you that you are rolling the dice and I wouldnt fix it either considering you are far exceeding design tolerances.. They simply wont hold up to the sort of power you want it too. I dont know if they knew what you are using it with or if they told ypu it would.

I am telling you G50 or expect that you will be doing this again soon.

If you are interested in one, let me know, but dont take this as biased advice. i learned the hard way.