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#1
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5 or 6 speed swap ?
On a 1967 GTO. We swapped the rear gear from a 4.11 gear to a 3.23. Because the owner didnt like how many RPMs it would turn to cruise The owner still is looking to make it smoother at highway speed. Now @ 60 mph its turning 2800. He is looking to be able to easily cruise at 75 to 80, and really wants more low end power. I thought going back to the 4.11 gear and a 6 speed. (Tremec Magnum 6 speed) or should he just stay with the 3.23 and go 5 speed? Any thought or recommendation from guys who have made the swap to a 5 or 6 speed?
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#2
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Get the Tremec TKX 5 speed so the floorpan does not need to be cut.
Has multiple OD gearing options. Done. |
#3
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I would have kept the 4 series gears and put in a Hone overdrive, as its a great way to go if the car has no H or X pipe in the exh system.
It handles big power, but you also due to its design get 2 in between speeds out of a 4 speed besides the overdrive!
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#4
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Go with a 3:73 or 4:11 gear and the 5 speed overdrive. I've done that combination for multiple customer's cars and it works out great for both low end and highway cruising.
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62' Lemans, Nostalgia Super Stock, 541 CI, IA2 block, billet 4.5" crank, Ross, Wide port Edelbrocks, Gustram intake, 2 4150 style BLP carbs, 2.10 Turbo 400, 9" w/4:30 gears, 8.76 @153, 3100lbs |
#5
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The 3.23 are ideal with a .72 overdrive. No need to change rear end gears. Or could get the .81 OD version even but 1st gear is not as steep (but not likely needed with Pontiac torque).
TCET18083 TKX GM 3.27 1.98 1.34 1.00 0.72 OD 3.00 reverse |
#6
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I just put in a TKX 5 speed with 3:27 gears (9 bolt BW). I have the .64 overdrive and 2.87 first gear. Love this combo. At 70mph just a hair over 2000rpm. The TKX is physically smaller than the TKO with same torque rating plus they upgraded the shifting mechanisms for 7500 rpm shifting , not really applicable for Pontiac’s. I did a lot of research on the 6 speeds and decided wasn’t going to use the 2 overdrives as much.
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#7
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I have TKX with 2.87 first and the .68 OD with 3.23 gears and I love it With the cam in my car which is Speed Pro CS1175R 224/234 @.050" HFT which is similar to the summit 2802 it cruises along at 70 mph right around 2000 rpm with no bucking or grunting power range is said to be 1600-5000 or so rpm perfect for what I'm doing. Bigger cam and these gears maybe not so friendly at this rpm/speed. The TKX is nice as said below very little is needed to install only a couple small cuts to make the shifter fit in the stock location on my 65 LeMans
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65 LeMANS , SD performance 462ci Engine, Tremec TKX 5 speed with a 3.73 geared 8.5" 10 bolt |
#8
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I also recommend the Tremec TKX 5-speed....very happy!
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#9
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I've had/have both 5 and 6 speeds. While I think they both have their benefits they also both have quirks I don't like but for what the owner of that car is looking to do Scott, the Tremec 5 speed will do everything he is looking for.
On our own personal vehicles I've run different Tremecs with .63 overdrive using 3.27 rear gears as well as 3.73's. The .64 version with 3.55's and several other swaps all with the 2.87/ .64 combo ranging from 3.50 to 4.10 gears. He'll probably be really happy leaving the 3.23's and going this direction. Generally with 3.73's and no overdrive, with a 27" tire I'm doing 60 at 2800. So he must have an extremely short tire to be turning that kind of rpm to do 60 with 3.23's. |
#10
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Again, late to the party. Look at this thread of the T-56 install in my "73.
https://forums.maxperformanceinc.com...d.php?t=839167 Not much to cut in post #15. Look at post #14 where a lot of surgery was done because the engine was an inch back from stock in a 1970 Formula. I have the T-56 in my 1970 T/A. Same deal not much cutting. It was already cut for a four speed, but the T-56 was put in without any further cutting. Same amount of cutting as my '73 was previously was done as it was an auto to stick conversion. I have another T-56 going into my 1970 GTO which was a factory four speed. I don't expect any cutting. Will update once it is in. |
#11
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Very pleased with my TKO 600 5 speed & 3:73's. The TKX was not announced or available when I did the enhancement.
Tim john--- |
#12
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2800RPMS @ 60MPH with 3.23's ??
Something does not seem right there..... BTW ...... Love my TKX with 3.27 1st gear....
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Troy Rockaway NJ 67 GTO 400HO / TKX 3.27 1ST GEAR-.72OD / 3.36 POSI HOTCHKIS/UMI/BILSTEIN |
#13
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Quote:
That was my thoughts. Must have orginal 4 speed tranny. I'd leave the 3.23's and install a 5 speed tranny as mentioned. The .72 would be nice. I have 3.73's with a TKO600 .82 OD. Cruises nicely for the speed limits here at 65 and 70 mph. Also have to consider where engine is happiest at cruise. |
#14
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Quote:
If tires were 26.5 - RPM's would be around 2400 - 2500. |
#15
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Number one complaint on the 6-speed is its huge size -- you will basically remove the complete tunnel on the 67. My TKO-600 required two dimples with an air hammer for clearance and the new TKX shouldn't need any tunnel alteration. Number two complaint is the car I drove with the 6-speed had a 3.90 rear and the RPM's were something like 1,700 with the .500 overdrive at 65 MPH. Number three is while the engine is loafing along with the 6-speed overdrive the 4.11 pinion (and driveshaft) is hauling a$$ and creating a lot of heat and wear at higher speeds. Might also want to do a critical speed calculation to see where the estimated driveline failure point will be.
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Mick Batson 1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 2+2 survivor AC auto -- 1965 Catalina Safari Wagon. |
The Following User Says Thank You to lust4speed For This Useful Post: | ||
#16
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Currently TKO 600 0.82 OD with 3.08's
Given a second shot I would have kept the 3.42's and run 0.67 OD Note however that your diff ratio determines prop shaft speed - narrower shafts may get too close the critical speed for comfort with higher numerical ratios. A wider aluminum shaft may make this issue go away. |
#17
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I took out the 3.43 rear gear and installed a cast iron T-10 with a 3.42 first gear and put it through a 2.73 rear gear. I had the Camaro rear end hub to hub and figured that it would be ok with the huge low end torque my engine makes. (look at my signature), I cruise at 70 about 2500 rpm. And I can cruise in town in 3rd read with the final drive around 4 to 1. And, I use 4th like an overdrive. But light throttle driving at 1500 rpm is no problem in 4th. These big engines with Rhodes lifters create so much low end torque the drivability is really good. .
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1979 Trans Am WS-6 .030 455 zero decked flat pistons 96 heads with SS valves 041 cam with Rhoads lifters 1.65 rockers RPM rods 800 Cliffs Q Jet on Holley Street Dominator ST-10 4 speed (3.42 first) w 2.73 rear gear __________________________________________________ _______________________________ 469th TFS Korat Thailand 1968-69 F-4E Muzzle 2 |
#18
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I have been using the 3.42 ST trans for years in a couple early big cars.I have 28 in tires on the 62 GP with 2.68s in the back and have not found it necessary to pull back to 3rd very often.434 CI with a 068 cam.FWIW,Tom
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#19
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Unless you get a screaming deal on a 6 speed, there is no practical advantage to the 6 speed and it will represent a lot of hassle that could have been avoided if what you are trying to achieve is simply lowering the RPM on the highway while having a nice shifting close ratio gearset.
I absolutely loved my TKO 600 with .64 OD and 3.73's behind my mild SFT 455. The 433 and OF cam are not all that happy lugging around in 5th gear at speeds below 55. I am now running FI and a 26" diameter tire which has improved things a bit. If I had it all over to do again, I would definitely go for the TKX and probably do the 2.87/.81 with a 3.42 gear.
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71 Formula 433, Splayed cap 400 block, 4" stroke Scat forged crank, 6.8 Eagle rods, custom Autotec pistons. SD 295 KRE D ports, Old faithful hybrid roller, Torker II, Holley Sniper Stealth, Tribal Tubes, TKO 600, 3.73 Eaton posi. |
#20
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The TKX is much smaller than the T-56. I see no reason to have the 6speed. The TKX fits the older cars so much better. Here is my TKX. Plus you can get many different combinations of offset shifters.
I have the 3:27 with 2.87 first gear and .64 OD. Formula8 is right with using 3:42, my car is very light so I get away with the 2.87/3:27 combo, heavier car might like 3:42 or 3:73. |
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