View Full Version : Dog Box dilemma..

01-31-2011, 02:05 AM
So I've found a used G-Force T-5 dog box for a good price. Unfortunately, I've talked to G Force and they've discontinued that box. They only have what's left on the shelf for parts for it, and expect that supply to only last 1-2 years.

so should I buy this box and convert the car to a T-5 only so I can run it for a few years (until I break a gear they no longer stock), and throw it away, or do I hold out for something else?

Another question along this line- I've considered a Saenz 840 as well, but the tranny is much wider than a T-5 and would require me to cut the tranny tunnel to make it fit. Would that be allowed in STU rules?

Appreciate any comments. :)

C. Ludwig
01-31-2011, 12:23 PM
Just throwing this out there; Quaife has five and six-speed dog-engagement gearsets for the Silvia case. Sequential and H-pattern.

01-31-2011, 12:56 PM
They sure do. They're around seven million dollars and fit the SR20 block. Since the only SR engines in the US were FWD and the heads can't be made to fit a RWD platform, so far I can't use it.

I'm hoping for a less esoteric transmission that allows me to get parts quicker and cheaper in the US. i.e. Richmond, G Force, Schwitter, etc.

01-31-2011, 01:21 PM

That is all. :)


01-31-2011, 09:12 PM
That's why I'm shopping the used market. They're not nearly as expensive used, but the issue is finding parts for them. the G force would be an awesome deal if only they made parts for it still.

01-31-2011, 10:32 PM
Matt, 4 speed Jerico, about 1700 on racing sites. Name your ratios. made to hold 750 Hp no prob. gearsets are 75 to 125. Do you really really need all 5??

02-01-2011, 02:15 AM
If I don't want to be swapping out rear diffs every other race, yes.
with the stock 4.1 rear diff, I MUST run an overdrive for 2 of the local tracks since I'm shifting into 5th halfway down the front straight.
for the shorter tracks, I use gears 2,3,4 on the stock tranny; on the longer tracks, I use 3,4,5.

I guess I could always hunt down a 3.6 or maybe 3.9 rear end so I wouldn't need the overdrive, but then I would suffer astronomically on the shorter tracks if I didn't swap the diff with my 4.1 or 4.6 between tracks. I'd rather spend a bit more money and get a 5 spd tranny with an overdrive on it and not have to constantly swap parts around.

I'm considering G force's 5 spd synchro box with road race ratios, but would rather go with a dog box. Any experience with how well the synchro boxes work and last?

02-01-2011, 10:29 AM
...I use gears 2,3,4 on the stock tranny; on the longer tracks, I use 3,4,5.

We run the same tracks. By your own admission above, you only use 4 gears right now. My 4 speed Jerico works great. I am in the sweet spot on my power band from 65-140mph, RPM drop is only 1300 between gears. I am not changing rear ends for TMS/TWS. First gear is 1.72 so it's a little sluggish around the paddock. You'll see this weekend at MSRH that a 4 speed does just fine, although I will only use 1-3 there. If you don't have a gear calculator, PM me and I'll email you one. I think you'll find a 4 speed is more than sufficient.

02-01-2011, 11:44 AM
I would be looking around for used stuff from ex pro teams. We have in the past found screaming deals on dog boxes for other cars, that with a little thought and engineering can be mated to Chuck's Prod car.

02-01-2011, 12:52 PM
We have two KC area EP RX7's running 4spd Jericos and they have been very reliable. They both used Y2K boxes with drilled shafts and lightened gears. One of the guys sourced his from a NASCAR team that was using it for roadrace qualifying. As others have mentioned - you use all four gears on the track.

To fit these in an first gen RX7 they did have to hack up the tunnel in the car allot. It is a big box.

I looked at the G Force transmission for my RX7 but I wasn't all that impressed with the gear ratios. Also, unless G Force corrects this, the 5th gear in a stock T5 is in single shear. I'm not sure It would be all that strong.

I'm going to use a Miata gear set in my car.

02-01-2011, 01:03 PM
Mark, thanks for the input. The issue is that 5th gear is an overdrive gear. on the stock 4.1 diff and current speeds & power levels, I run out of 4th gear at start line of TWS and am at/near redline in 4th in 2 or 3 places at MSRH. In order to still have enough RPM at 1:1, I would need to spend another $1200 to build another diff and run a 3.6 rear end.

OR, I can spend that $1200 difference to get a 5 spd transmission and run the 4.1 and 4.6 diffs that I have currently. I'm not sure which is better/faster in the long run. I really need to sit down and do the calculations, but I need more data than just lap times and end of straight speeds to calculate that- I need corner exit speeds and whatnot, which means I need to borrow a friend's DL1 and run it at each track.

another thing I'm factoring in is that I'm at only ~150whp right now and have no aero. Eventual plans for the car are ~250-300whp and aero, so I'm trying to plan for the future as well. The eventual goal for the car is at least 10 sec/lap faster at MSRH and 15 or so sec at TWS.

Thus, I'm trying to plan for the future in a way that doesn't leave me stranded now. the stock transmission in these cars starts breaking about 200hp, and the one I've got had dying synchros in 2,3,4th gears. It's going to need replacement soon, so I might as well buy a tranny that I can use for the long run.

Long story short, I'm not sure a 4 spd would let me go any faster for any cheaper considering I'd have to invest in yet another differential. the cost difference between a 4 and 5 spd is about the same as buying another diff.

15 ways to skin the cat- just trying to figure out what would be best in the long run. :)

02-01-2011, 01:50 PM
Matt, the only problem I see is that it will take much more tham 1200 to get the 5 gear in the tranny. All I could find was the Jerico 5 speed ($6000) and than Quaife, Elite etc($8000+)! A short nose R200 could be had for quite a bit less. Also, most any racing tranny will have a 1:1 top gear (whether 4 or 5th). So, back to different diffs!!

02-01-2011, 05:22 PM
that's what was so nice about the G Force boxes- they run a true overdrive, and can be bought used for $2000-2500. I've seen some 5spd w/ OD trannies out there in the 3500-4500 range as well, but were already sold.

02-10-2011, 08:49 AM
Matt, you can use an overdrive 3rd gear in the Jerico 4 spd and you just flip the shift arm. Then the 1.00 4rth becomes 3rd and your overdrive 3rd becomes 4rth. The Nascar guys do it all the time. Go to the Jerico site and look at the available overdrive ratios. You really do not need a pit gear.

02-10-2011, 11:54 AM
Now we're talking some sense! I even called the Jerico guy and talked to them earlier this week, they said my only option was a 5 spd w/ overdrive. never mentioned flipping the shift arm like that. I could care less about a pit gear- the engine makes enough torque that I can get moving pretty easy. the big issue is being able to run an OD so I can get away from having to spend another $1500 on another differential.

Thanks for the info- you just made my day! :)

02-10-2011, 10:00 PM
Call Scott at Taylor http://www.taylor-race.com/ - they really know their stuff and are just a few hours north of you.

02-10-2011, 11:52 PM
Under no circumstances call Taylor unless getting boned up the ass is your idea of a good time. Nobody will run you into the poorhouse quicker. There are many Jerico builders in the North Carolina area. You have been warned.

02-11-2011, 12:24 AM
Yeah, talked to Scott on Monday or Tuesday. he suggested a Sierra 5 spd they've had on the shelf for umpteen years. hmmmmm- more than I paid for the whole car...

02-11-2011, 09:36 AM
Well... If its been on the shelf for years, then I think the should let it go mad cheap!

Had to laugh at the differing reviews! No shop can keep everyone happy... And of course the more expensive ones must be better right? lol

02-11-2011, 10:35 AM
They're still selling it for "about what we paid for it just to get it off the shelf" but it's still more than I paid for the car & cage & suspension.

I've heard very mixed reviews about Taylor as well. I have a place here in town that can do any work that I can't do myself, but it's nice to be able to get parts close to home. I may just use them for parts as needed and leave the detail work to a local engine & tranny shop.

03-28-2011, 09:55 AM
Small update for anyone who cares..
Found a deal on a GForce GF4A over the weekend and bought it.
the gearing is a bit off, but I figured I'd have to do a bit of reconfiguring anyway.
for the price I paid for it, I can replace all of the gears in it, custom bellhousing adapter, clutch, flywheel, etc, and still be ahead over buying a new Quaife or Taylor box!

04-24-2012, 05:35 PM
Can we run dog ring boxes in STL? I am still looking for all the do's and don't for STL.
Keith V:shrug:

04-25-2012, 09:39 AM