tremec T-56 vs T600 - Page 3

blykins · #41 (**permalink**) 06-12-2010, 07:53 PM

I carry the whole Tremec transmission line. Shoot me an email or PM and let me know what you're looking for...

Rwillia4 · #42 (**permalink**) 06-12-2010, 08:10 PM

Dang, that was a quick answer!!!

Excaliber · #43 (**permalink**) 06-12-2010, 08:48 PM

Well I wouldn't recommend the 2.29 first gear ratio myself. Thats even higher than a Close Ratio top loader 1st gear ratio and that Top Loader is considered "to high" a gear for most folks.

I had one, drove it for years, it was great on the highway, AFTER you got up to speed, say 60 mph and above. But it's kind of hard to "play with the gears" when second is good for 85 and 3rd to 115 or better. The concept of the high 1st gear was for road racing. You needed the top three gears to be "close" to work the corners. You would rarely if ever use 1st gear. "Playing with the gears" makes perfect sense in a road race car, where your running 85 to 150 mph. Try that on the highway and you won't keep your license long.

I say go with a 2.7-2.8 or so 1st gear ratio, with a .8 over drive. Possibly a .6 IF your running super low rear end ratio. That being the case, then maybe a 2.2 1st gear starts to make sense. What rpm do you expect your cam profile to work well in? There's a LOT to picking out the right gear ratios, it needs some serious thought.

I would think by now the original post/thread starter has already made his decision. I wonder what he eventually ended up with? I went with the TK0-600 myself, from Brent (B2 Motorsports), with a Steeda Tri Ax shifter. WOW, it's WAY better than that close ratio top loader I had. A lot more fun in the lower mph zones.

mattpatt · #44 (**permalink**) 06-12-2010, 09:47 PM

I'm trying to find the Tremec with 2.29 first - no luck. Who sells it? what's the part number? What's the torque rating? The close ratio gear ratios would be perfect in a cobra with a 500+ hp SBF, 3.45 rear and 275/40R18 tires.

Anyone got this info??
thx

Matt

mattpatt · #45 (**permalink**) 06-12-2010, 10:17 PM

I'll PM you Brent.

Excaliber: Here's my thinking. I had a 1970 Chevy Nova (396, ~425hp, 3400 pounds, 3.55 rear). It had a close ratio 4 speed 2.20 first that got just over 60 mph out of first (7200-7600 rpm but smaller tire diameters). It had absolutely no problem getting going (easily peel the "slippery" wheels thru first and could smoothly pull from a stop in 4th. The SPF cobra I'm considering, at ~2500 lbs with a ~550hp SBF 427 and 3.45 rear will get 60 mph in a 2.29 first (275/40R18 tires with 3.25% "squish"). Calculations suggest that the coefficient friction of the old Nova tires was ~0.9 while modern tires (calculated fro Corvette stopping distance from 70 mph) is ~ 1.15. Adding in wheel base factors and center of gravity heights to get weight transfer and correcting for effective weight increases from rotational inertial moments (~600 pounds in first) indicates that even with a 2.29 first the cobra will still overcome the tire grip capabilities in first gear (i.e. there's still wasted power). With the 2.29 I would expect, from what I've heard about cobras, that a little less ability to over-power the tires in first may actually be safer (less likelihood of spin-outs) and more controllable. Bottom line - in first it looks like way better than the Nova and still tire limited. Finally, with the very close ratios, the 6the gear doesn't go so high that it's unusable for cruising at 60 - 70 when you consider I'm planning on fuel injection to keep the torque and smoothness good at ~1800 rpm or so. So help me here. I don't have the cobra experience you (and the others here) have. What am I missing? I'm about to make a very expensive decision and need all the info I can get.

thanks, VERY much for any help with this.

Matt

mikeforte · #46 (**permalink**) 06-13-2010, 09:43 AM

Hi Matt,
The 2.29 1st is not a gearset available in a new T-56. That is one of the gearsets for a racebox.

Quote:

Originally Posted by mattpatt

Do you know who sells it? The part number? The torque rating? The ratios would be perfect for a street use cobra with 500+ hp sbf.

thx

Matt

mikeforte · #47 (**permalink**) 06-13-2010, 09:46 AM

Hi Matt,
I am not aware of a 2.29 1st gearset for a TKO. In the 17 years of dealing with the Tremec product line, I've never seen it.

Quote:

Originally Posted by mattpatt

I'm trying to find the Tremec with 2.29 first - no luck. Who sells it? what's the part number? What's the torque rating? The close ratio gear ratios would be perfect in a cobra with a 500+ hp SBF, 3.45 rear and 275/40R18 tires.

Anyone got this info??
thx

Matt

Excaliber · #48 (**permalink**) 06-13-2010, 11:06 AM

Well your right on a couple of important points. Safety, no doubt a higher first gear ratio is safer, but not nearly as much "fun". Power, no doubt you can easily overcome ANY available traction, even some mean slicks will still go up in smoke with a 2.29.

What I found with this ratio:
You can forget about parades! Now that wasn't a big thing for me, but there were times when I wanted to and it just was a major PITA constantly working the clutch with that high gear ratio. Cruising around town at low speed, same thing, just not pleasant. Even with fuel injection depending on your cam and intake profile it might be tough to get a motor to run smoothly under 2000 rpm or so. 2000 rpm, combined with a 2.29 ratio and thats the fundamental problem with the high gear set for around town and parade duty.

Two: You would be well advised to get a bad ass clutch with this ratio! The new Vette's run's a similiar 1st gear ratio, with a dual clutch and a 3.41 rear gear, 26.5 inch tire. I had mutilple clutch problems with my ERA (Side oiler, dual carbs, easily 500 plus horse), steadily increasing the size, clamping force and friction material to get one that would live. Steep entry parking garages, or haveing to start on a hill, loading the car onto a trailer, etc. was not pleasant. You end up slipping the clutch, overheating it.

At freeway speed or above that ratio was cool. I loved dropping down into 2nd and blasting through the gears. Of course when your talking 80-85 mph in 2nd and 115 or so in third that pretty much limits the places and times where you CAN "go through the gears". It worked well on a road course, not so much on the street. It was not ideal for the 1/4 mile either. I would be shifting into 4th as I neared the finish line. Auto Cross, where speeds are typically 60-65 mph was right at the top of first or the bottom of second, neither was ideal. Again, "road racing"? Not bad at all, worked well for the 1% of time I actually used the car for that. The other 99% was OK, but far from perfect.

A wide ratio top loader has gearing very close to the TKO road racing spec trans with .82 overdrive. Which is what I'm using now. I find the 2.87 (or so) 1st gear ratio is considerably more fun on the street and cruising around town. Overall I would rate the gear ratio's as "perfect". 3:31 rear gear, 26.5" rear tires. I've had all kinds of different tires on the car. The best for track work are the Goodyear yellow letter slicks. I run a pretty tight auto cross track here in Oregon and find these new gear ratios, with the slicks, work really well to keep my engine in the power band.

Now the T5 typically comes with a 3 something 1st gear, I think you can get that in a TKO600 as well. DONT GO THERE!!! That is ridiculously low. In fact I would prefer a slight higher 1st gear than the 2.87, but no freakin' way a gear into the 3's or past a 2.6-2.7 or so.!!!

There have been reports here on CC of folks using SECOND GEAR for the hole shot at the drag strip and making their best ET with that. Usually because 1st gear ratio is just to dam low. However, those same folks also were replacing the clutch following that 2nd gear hole shot or killing the clutch right there on the track!

blykins · #49 (**permalink**) 06-13-2010, 11:24 AM

A 2.87 1st gear, like in the TKO 600 is just fine and it works with a nice variety of rearend gears. If you ride in a Cobra with one, I think you'll see that needing such a high 1st gear ratio is a non-issue.

The difference between a Cobra and a Nova is night and day. A 2400 lb car with 550hp will light the tires no matter what 1st gear ratio you have.

I'm offering a package deal right now on a TKO 600 transmission, Quicktime bellhousing, RAM flywheel, RAM clutch kit, and accessories. This combination works perfectly for a Cobra.

eracoast · #50 (**permalink**) 06-13-2010, 12:58 PM

any of the tko's are plenty strong for these light cars, the back tires will brake loose way before any damage to the trans will happen, they are strong,strong,strong!! As far as T-56 6 speed goes, half the time you never use first gear anyway, besides it takes extra HP to turnover the extra gearing. 5-speed the way to go. 428 FE 550 HP Tko 500 3.54 rear with 48,000 mi. never had a problem. Have fun and be safe and don't let it get away from you !

mattpatt · #51 (**permalink**) 06-13-2010, 06:21 PM

Thanks guys,

You've all got the experience I don't have and I appreciate your steering me away from the 2.29 (even if I could get one). Now I have to think about the pros/cons of 5 vs 6 speeds and 2.66 vs 2.93(?) vs 2.83(?). I'll probably be back with more questions later (I'm installing the engine myself).

Thx again!!

Matt