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Mike - the drop in rpm's is just too much with the 0.68 5th. For me, it is just an gear for highway crusing, even with a very torquey stroker motor.
With 255/50/16 rear tyres, I pull 2100rpm at 70, 3000rpm is 100mph. When really "getting on it" that tall 5th is a bummer. When just "pressing on nicely" it still annoys me, such is the gap between 4th and 5th. Only time it is OK is steady speed highway cruising, and you don't get to do a lot of that in the UK! Nope, with hindsight I definitely would have gone for the 0.8 5th, even at the expense of some more rpm's when crusing. Just MHO of course. Wilf |
Guys
The Tremec 5th gear is an OVERDRIVE. I have the RR version with the .78 but I use it strictly on the highway for cruising. And it works. I have a 4.11 rear and first is DEEP but the car is running 1.40's 60' times as the motor pulls 8,000 RPM. On the other hand I took a trip a while back and the 6 got right around 22 miles per gallon at 75MPH. Not bad for a flowed 1000 CFM Holley. Motor just purred along. I'm running 275/40/17's on the rear.
All in all I'm really happy the the Tremec. I looked at all the options and couldn't get everything I wanted in any trans so the Tremec was my choice. So far so good. The only complaint I HAD was it was very notchy until it broke in. ie no powershifting at run and gun. 300 miles later it was fine and, SO FAR, no testing of the rev limiter on any missed shifts. So far... Regards, |
I am also very pleased with my Tremec 3550. Of course the .68 fifth is just overdrive. My God! I've turned 120 in fourth gear. What the heck are you looking for??
I love the fifth on long trips. Just smooths the engine down to a nice purrrr at about 2k. Roscoe |
Roscoe - different strokes etc. My car tops out at 135mph in 4th. Drop it into 5th and the revs come down to 4000, acceleration drops right off. It's frustrating. With the 0.8 5th I would end up with better acceleration right up to the final top speed of 165mph, although it has pulled this with the current gearing. Just took a long time. (seemed like forever).
If you got the ponies, you gotta use them. The only thing I sometimes think about is the air pressure on the windshield at those speeds - and all held in place by 6 tiny little screws!!! |
Wilf,
Cobra start to loose their aerodynamics at about 150. I don't think I would feel comfortable going 165 in a Cobra, or any open car for that matter. I understand that you can change the gear in the Tremec to anything you want. Maybe reconsidering your total gearing and taking a peek at your rear end? Does that make you randy? YEAH BABY YEAH. Never mind, I meant differential. Also, most gear changes will drop the rpm about 1500. That's why one tends to pass the shift point by about 500 and maintain the power curve. Maybe a rear gear change will help. Roscoe |
Roscoe - I have to say that I am extremely pleased with the stability of my car at high speeds. Even on my semi-suicidal "lets find out the top speed of this sucker" run it felt OK. Front end didn't lift, stayed planted firmly, no wandering. But there again, my car is a Crendon, fairly heavy, and best way I could describe it is as a Kirkham with a fibreglass body. Same chassis and stuff, just has jag rear end.
I think my rear end ratio (ooerr) is fine - the first four gears work well, just wish I had known about the alternate ratio for 5th. I think I might just change it one of these days - probably at the same time I pull the engine for some more work. Couple of years off I suspect. |
Roscoe-
what rear gear ratio are you running? What rpm are you turning at 70 or 75? And thanks to everyone for the responses. Mike |
I'm running a ford 9" with 355 gears. At 70 I'm doing about 1800-1900.
Roscoe |
I am runnig the 3550 with a 351w/396 in my SPF, the majority of my driving is off track so I am happy with the .68. I am thinking of changing to the T56 6 speed which seems to give you the best of both worlds but is quite a bit heavier. I have an acquaintance that spends a lot of time on the track in addition to drving the car almost daily on the street and he is very happy wiith tnhis set up. Perhaps others have experience going this way?
Chas |
Roscoe-
If you've got 355 gears and are turning 18-1900 @ 70, maybe I want the .83 with 3.31. By my calculations (which are always suspect) with 3.31s and .68 that would put me at apx. 1700 at the same speed- maybe too little rpm? How short is first gear for you with 3.55s and the 3.27 1st in the Tremec? Mike |
First gear in the Tremec is like a Harley. Lots of torque but very short. Just to get you started.
Third is my really strong gear. Roscoe |
First gear is nearly useless with 3.73 rear gears. It works in bumper to bumper traffic.
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Going back to something I posted the other day, does anyone know whether the shifting is any different on the tranny with the .83 than it is with the .68. I was told that b/c of the hardened gear set, shifting would be more difficult with the TKO II and therefore the regular TKO was a better choice for the street. This doesn't make much sense to me b/c I think only 3rd gear is hardened in the TKO II and why should a hardened gear be more difficult to shift than a non-hardened gear set?
Thoughts??? Thanks |
tremec
THE best overall rear end tremec combonation IMHO is the TKO with road race third and .83 fifth combined with a 3.08 final rear end for the following reasons. first gear with it's 3.27 ratio will give you a 10 to 1 ratio which is perfect for launching with less wheel spin and not over reving then you will really love what 2nd and 3rd will do for you because you will be right in the sweet spot of engine power band then in 4th at 60 mph you will be in they area of 2400 or 2000 in 5th if you are so inclined or your engine does not resent or protest being that low and finally in 5th at 70 which is a acceptable hiway speed you will be in the vicinity of 2300 sweet it does not get any better than that mind you this was calculated with 295 50 15s and will mostly apply to engines making the vast majority of torque under 5000 rpm which is typical for a street stip road race autox weekend warrior ect
thanks kanuck |
Wilf
Re your>>>If you got the ponies, you gotta use them. The only thing I sometimes think about is the air pressure on the windshield at those speeds - and all held in place by 6 tiny little screws<<<
I, too, have thought about that BUT I think if you look at your windshields side rails they are curved on top. I think, might be wrong, that is how the windshield is held down. The screws certainly keep things together also but the curves on top take a lot of the load. IMO, of course. Regards, |
Chaplin,
I've spoken with a few people who say the best shifting on a tremec occurs when you use the midshift kit, which moves the shifter platform up to the middle location instead of the stock rear location: http://a9.cpimg.com/image/69/66/1148...-02500190-.jpg Supposedly it makes a big difference and the tranny then shifts much quicker with lower effort... Mike |
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