Broke another gear, PICS. suspension prob? Added Vidio link

[sc68z28]

The damage you see here happened at launch. I am being told it is suspension related.

Notice the bent shock tab, bent Slide-A-Link, and even the leaf spring up at the front mounting point.


This gear set has 250 miles and about 14 to 18 passes on it.


Your opinion.

What would you do? Cal Tracs W/Split monos, 4 Link, Ladder bars? I'm open, and just want to do it right.

The car has about 800hp, I've been launching off a two step at 4000rpm (stick car) my 60 foot times suck about 1.65 to 1.70 average.
It is driven on the street about 500miles a year, can I use a pro gear? ---

Vidio link http://www.youtube.com/watch?v=bICeq235yf4

[sc68z28]

Oh, here's a pic of my car at launch (1.63 60') at about this point the tires usually unload.

[John_Heard]

I'd suggest switching to a regular cal-trac bar to get rid of that rubber biscuit in the link. Also get rid of the rest of the rubber around the springs. Aluminum bushing up front too if you don't already have one.

You're probably going to need a pro-gear to make it survive long with that stick. I don't have to tell you an automatic would probably be easier on parts. Can you soften the clutch up?

[TubbedTruck67]

I would go with a caltrac setup, everything Ive heard about them is good and there proven to work on many cars. Ive heard not to run a pro gear on the street at all. Im not sure why, or if thats right but Im sure somebody on here does.

[mnr67]

Bill,
Quick answere- Pro gears are softer to handle the shocks encountered a the dragstrip, but because of the lower hardness, will not last long under normal street use. Street gears are harder to provide better wear, but the higher hardness also makes them more brittle.

I've been following your progress with interest as I have a similar car with similar problems (67 camaro, 470 BBC, Tremec 5 speed, 9" with 4:11's, street car). I too have spent the past summer breaking parts while launching at 2300-3500 rpm against a 2-step. I run 11.50's at 123 with 1.80 60' times on 28" tall M-T drag radials (275/60-15) while driving to the track. Rear suspension was Landrum 225# monos with Slide-a-links. This set-up never really worked - could never completely eliminate wheel hop - it would hop in the burn-out box. Cranking preload into the slidalinks actually stiffened up the springs, and jacked the ride ht way up. Result: no rotation, no traction, 1.95 60' times. I had 1" lowering blocks, but literally smashed them-there gone now, then bent the 7/16 wheel studs - now have 1/2", then bent the Landrum springs and the spring perches. Now have Caltrac Split Mono's (200# 1" lower ride ht), and I converted the Slidealinks into a caltrac of sorts. Rear ride ht is much lower (maybe should have gotten stock ride ht springs), and more importantly much softer. Adjusting the caltrac bars does not require so much preload as to cause a change in your spring rate - only made 2 passes, but the rear end was squatting now and the tires were hitting the fenderwells - so done until next year.

[mnr67]

Bill,
A few more thoughts on your ring and pinion problems. There are numerous guys around here (milan dragway-MI, Norwalk-Oh) running low 10's with street gears. If I remember right, you are running a richmond 5 speed with 1:1 5th gear, really steep 1st gear, with a relatively tall rear end ratio (3.42:1 or so). I believe the low torque multiplication of your rear gear ratio is placing higher loads on the rear gears. This is in comparison to running a higher 1st gear in the trans (lower numerically), with a steeper rear gear ratio (like 3:89, 4:56 etc).

With a higher rear gear (like 3.42:1), the ring gear is smaller in diameter, this means that to produce an X amount of torque at the axle, the force on the ring gear teeth must be higher than if the ring gear was larger in diameter - like a 4.11 or 4.56.

I understand changing all of that is an expensive proposition. The downside to an overdrive trans with a steep rear gear is that at highway speeds, the driveshaft rpm is quite high, compared to your setup of 1:1 fifth gear with a 3-series rear gear. But, I think you are paying the price at the track.

Hope I'm helping, and maybe we can learn from each other, and the other excellent members of this board.

p.s. I'm no expert at drag race technology, I'm just a mechanical engineer/motor head who's been racing for 30 years (dirt bikes, go carts, late model stock cars, drag bikes, street cars).

[kyleracer]

I am running pro 4.11 - 12 bolt gears in a BBC street/drag car that weights 3400lbs @ 10.40 - 128mph for 14yrs without breaking them. Also drive to the track and to car shows with no problems -I use syn. gear oil- but it is with a automatic trans. I have had the lash adjusted 1 time to keep them quiet.

[mnr67]

There's some more real world data - 14 yrs street/strip car with Pro gears and one lash adjustment required for noise. I have ~18yrs on street gears, street/strip car (3640lbs, stick shift) with no lash adjustment and still quiet. From these 2 data points one could conclude that pro gears will last an acceptable amount of time in street use regarding wear, as long as you pay attention to lash conditions/noise.

[JeffMcKC]

Is your shock set real stiff on extension to bend it in that direction like its not getting longer if its winding up that much its not got much body separation to it in your picture. I would like to see a set up pattern it has just the heel of the gear broke and if you run a tight backlash and a good pattern it should be hard to break, a softer clutch would be a real good idea to help hit on the gear and the tires as your picture does not look like a car with 800 hp leaving the line make sure those shocks are not topping out that bracket is a real worry to me and maybe why its unloading

[sc68z28]

If I remember right, you are running a richmond 5 speed with 1:1 5th gear, really steep 1st gear, with a relatively tall rear end ratio (3.42:1 or so).

Yes, you are close, it's a g-force trans (similar) 1:1 5th. I was 3.0:1 rear gear, then 3.25, new gears will be 3.50, street gears. I have wondered if my 3.25:1 1st gear is adding too much torque to the tall rear gear. I need to open the trans soon to fix a leak anyway, and will change 1st gear to around a 3.0 to 2.95 , 2nd is 2.22 , far enough away to be ok, I think.

Is your shock set real stiff on extension to bend it in that direction (Quote from JeffMcKC)

No, I had turned it all the way down to one, just a few runs prior (QA1 single adj.)

I have been reviewing the vidio over and over again, and now have a new theory. Coming out of the burn out box, it acted funny, it grabed early and felt wrong. I think it had lost the preload on the left side. So when I launched, it went into bad wheel hop (i felt that) then it broke the gear, about 5 feet out.

Wheel hop will KILL gears, so I'm told, by three different sources.
I'm guessing the hop also is what hammered the suspension parts.

There is a race-car chassis shop near me that says he can fix my problems, with a ladder-bar / coil-over set up, will see?

Thank you all for your replies, anymore thoughts I'm listening. ---Bill.

[JeffMcKC]

When you went all the way loose on the extension it goes all hard on comp. on a single adj. shock get some doubles

I would go with a floater and ladder on a mono leaf if you want to stay in a stock 10.5 style car, if not go with a coil over double adj shock so you can tune it a lot better you should get by with a 115 spring in the back and wind it up

[John_Heard]

I'd stay away from that ladder bar coil over setup, that's not any faster than current stock suspension cars. It's more adjustable, but not worth all that hassle and cutting the car up. That higher 1st gear in the tranny should take out some of the punishment to the rear gears. I'm not a clutch guy, but I would bet you will find some benefit to having a clutch that isn't locking up right at the hit. Might want to give some clutch people a call and discussing the setup.

[sc68z28]

I would bet you will find some benefit to having a clutch that isn't locking up right at the hit.

John yes, I agree, a hard hitting clutch would be adding problems. When I pull the trans the clutch will be inspected. It is a 2 disc/diaphragm set up.
http://www.mcleodind.com/downloads/New_4_2007.pdf but not a dual friction, so it's pretty soft and very smooth off the line.

I'm still looking very hard at a ladder bar set up.

[sc68z28]

get some doubles

Ya! Doubles all the way.

[clutchdude]

My car is similar to yours. So i can say from Experience make sure those shocks are not bottoming out....i left mine in the stock position in front of rear because they had less travel than the comp eng. shocks that were on there before. So i didnt want to mount them behind the axle because the cal tracs cause alot of chassis seperation.

And i like you also do not have a adjustable clutch! You can make your car work with a streetable clutch! But something has to be able to give....for me i use a 10.5 x 28 tire i can get enough wheel spin so i dont dead hook. When my car used to dead hook i have crushed a axle housing and broke ring gears.

As for cal tracs...well i like them i have gone 1.301 and there springs? i only have a few runs on them but have went .2 better than my previous best? i think it was a great day at the track...but who knows

Also if your not running enough gear in the car the car would try to dead hook or blow the tires off the car.....like i said before dead hook brakes parts on manual trans cars.
Good Luck Jim

P.S. if you ever go to palmdale let me know, i would like to see your car run

Also i run ford motorsports street gears in my car with over 100 runs on them