Top Speed at Various Tracks?

SoundGuyDave

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The Rockland does have the holy grail of gear ratios. My motor is happy from 4K - 7K, so I could stay with a 4.10 rear gear and get the same numbers your looking at with the 3.73 gears. 2nd is very usable, 3rd pulls just long enough, 4th-no change, and with 5th being a 0.84 it may be usable. The 0.68 5th gear ratio in the TR-3650 brings my car to a near stall. Is anyone using this tranny? And using 5th gear on track in particular?

When I shift to 5th, my car starts to shutter a little. It's not a comfortable sensation. Am I seeing the beginning of the end for my TR-3650? How does one know their tranny is "on it's last legs" as Dave puts it?

[\politics]

I haven't driven one of the RSG T56 boxes before, but I know their rep is absolutely solid. I think you're reading the numbers right; usable 1st for tight hairpins, absolutely usable 2nd/3rd (depending on exit speed, really), 4th is the same. 5th... I had the Astro RoadRace 5th (.81 from memory) T5 in my old CMC car, and yes, it was absolutely usable. In terms of pull, shifting 4-5 FELT almost the same as 3-4, and while that 302 (Windsor) was set up to spin to 8K, it was all noise and heat at that point; the powerband was all done by 4500 or so. Yes, the RR 5th made a BIG difference at the big tracks (3.55 gears), and the RSG ratios are "close enough" to predict the same results.

I'm not sure what you mean by "shuttering" when you go to 4th. Is it at all times in that gear? Is it ground-speed dependent? 4th is a direct-drive, where the input shaft is directly coupled to the main-shaft, so that takes the cluster gear out of the equation.

With my 3650, the 1-2 synchros are GONE, and the 2-3 are solidly on the way out, so it has to come out and get refreshed. I'd rather put that money into a trans that I don't pathologically hate... The RSG is also a "Magnum" style trans, without a remote-mount shifter, so... It's just a pricey piece, particulalarly when you option it out.
 

Boone

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When I shift to 5th, my car starts to shutter a little.

Poorly worded on my part. Lemme splain...

While IN 5th gear doing 130-135mph going uphill at WOT on the back straight at VIR, my car has a vibration. It's not speed related. I don't feel the vibration in any other gear. It only happens in 5th gear on track, and I don't feel it at highway speeds. This is one of the reasons I'm going to change the rear gear to stay in 4th on the straights at VIR.

I have no shifting issues that aren't operator error. The clutch is a new McLeod RXT that went in with the 5.3L NA performance motor about 4 months ago.

Writing that last paragraph helped me make up my mind. I'm going to just put a rear gear in the car to take the shift to 5th out of the equation for the time being. I'll worry about the ultimate combination of rear gear and trannys when I have to go down the road to replacement that you're (as in Dave) heading down.
 

SoundGuyDave

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My suspicion is that it's in the driveshaft. IIRC, the overdrive gear is "just another gear" on the cluster on a 3650 (unlike on a T5), so I can't think of the mechanics that would create a 5th-gear-only-high-load vibration.

That said, if you're only noticing it around 130mph and above, I would suspect something past the tailshaft on the trans. Driveshaft, differential assembly, hell, even tires and wheels. They're all spinning a LOT faster than you'll ever experience on the street, and what could be "just fine" at 85-90 will start to go pear-shaped on you at 130. If you change your gearing to avoid 5th, but still keep the road-speed, nothing in the back end of the driveline will have changed, and you very well may still have the vibration.

If I were you, I would take the car to a SOLID driveshaft shop to have them assess things. Still running the factory 2-piece, or did you go to an aftermarket prop shaft?

This may be simpler and cheaper than you think...
 

Boone

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I'm running an aluminum DSS one piece. I have had the shaft checked at Oliver's Driveshaft in Winston Salem about 2 years ago, and it was spot on. I'm going to go through the drive train this winter, and I don't think I'm going to like what I find in the rear end. I'm hoping I do find issues so I can rule out the TR-3650. The fun fund for next year is likely to be starting out a little underfunded.

Seeing straightaway speeds corresponding to 1/4 mile trap speeds for 1000hp, 9 second drag cars humbles me as to the dangers of our hobby. Think of all the mandatory safety equipment required by the NHRA for a 9 second car. I am willing to be that very few of us even come close to those standards. I take the approach that the best way to avoid a mishap is to bring the most solid equipment possible to the track. I'm planning to take my car to Mike Roush's shop in Richmond, VA for a sanity check. Beyond that, I'm willing to accept that it is my ability is the ultimate factor for my personal safety.
 

46addict

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Here is the NHRA quick reference chart if you want to compare.
 

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2012Coyote

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I was going over 150 at Mid Ohio on the back straight, running my street tires (Mickey Thompson Street Comp 275/35R20's) and Stock Brembo Rotors with Hawk Ceramic Pads.

The first lap pushing it to over 150, no problems, the second lap, though, my brakes completely faded out and had to put the car into the corner sideways to slow it down and keep it on the tarmac. Then all the laps after that I was letting off at about 130 at the kink and braking gently. Getting power to go fast is easy, remembering to have brakes capable of slowing it down is sometimes harder, i learned.
 

Boone

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Beyond that, I'm willing to accept that it is my ability is the ultimate factor for my personal safety.

I did the rear gear change to 3.55s this winter. New rotors and Carbotech pads (XP12) all around. Should be able to go fast and stop... right?

Wrong. At 138.8mph at the end of the front strait at VIR, I get on the brakes for turn 1. The ABS has taken a dump on me (I didn't know it), and I lock up the right front immediately and go for a ride straight through the corner and come to a stop in the sand pit about 20 feet from the tire wall. Flat spotted the tire, and I'm done for the day.

Point is... I thought I had all my bases covered, but through the grass I went. On the bright side, I did add 10mph to my straight speeds compared to shifting to 5th with the 4.10s. Some parts of the track saw no gains (or even losses) compared to previous split times. Overall, I did take 5.5 seconds off my previous best lap time (now 2:13.96 on street tires). That's only about $300 per second off that this is going to cost me.
 

Speedboosted

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I did the rear gear change to 3.55s this winter. New rotors and Carbotech pads (XP12) all around. Should be able to go fast and stop... right?

Wrong. At 138.8mph at the end of the front strait at VIR, I get on the brakes for turn 1. The ABS has taken a dump on me (I didn't know it), and I lock up the right front immediately and go for a ride straight through the corner and come to a stop in the sand pit about 20 feet from the tire wall. Flat spotted the tire, and I'm done for the day.

Point is... I thought I had all my bases covered, but through the grass I went. On the bright side, I did add 10mph to my straight speeds compared to shifting to 5th with the 4.10s. Some parts of the track saw no gains (or even losses) compared to previous split times. Overall, I did take 5.5 seconds off my previous best lap time (now 2:13.96 on street tires). That's only about $300 per second off that this is going to cost me.

Have you weighed your car since doing the BBB motor? I'm in a similar boat with gear ratios. My car doesn't make the power yours does but right now the 3.31 are just too sluggish everywhere. Likely doing 3.55 as well and sticking with the 3650 for now. I have a 6060 sitting here but honestly I like the 3650.
 

Boone

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I haven't weighed the car as a before and after the engine build. I estimate my BBB added 30 pounds to the front end. To counteract the additional weight, I used Prothane mounts trimmed 1/2" to lower the CG of the motor. The net handling effects (and what I feel the cause is) are as follows:

Car understeers under braking if I try to add too much wheel. (additional weight in the front overwhelms the tires)
Corner exit understeer has improved. (additional weight in the front balances the car as weight transfers to the rear)
I can't break the rear end loose to induce oversteer easily. (taller gears and stickier rubber)
Sluggish corner exit. (taller gears = less torque to the wheels)

I'll address all these from a driving style perspective. My lap times came down more than I expected, but not all of that is attributable to higher straight speeds. I added about 10-15mph through the uphill esses. Two seconds of my improvement came in that sector, which has nothing to do with top speed.
 

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