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Discussion Starter · #1 ·
After replacing the heads on my drag car, the engine wants to rev much higher and faster than before. Because of that, I changed the rearend ratio to a higher one only to slow the engine at the finish line. The question I have is that with the higher rear ratio, I have thought about replacing the stock first and second gear assemblies with an aftermarket lower gear kit to help the car accelerate like it did before with the lower gear set while still retaining the high gear ratio. Does anyone have any input other than computer simulations (i.e. real life) regarding the use of low gear kits? It looks good on paper but is it worth it? Thanks...
 

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Your engine revs higher now and then you put less gear in it? That seems backwards.
 

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Discussion Starter · #3 ·
The engine runs a stock crank and in the past has crossed the traps at about 7000 RPM. With the addition of the new heads, it crosses now at 7400-7500 RPM. The heads made that much of a difference. I think for longevity reasons that is a bit much for a stock crank. So a slighlty higher gear was added to slow the engine back to 7000 RPM. In order to recoup some of the gear that was removed, I am thinking about a low gear kit. That's the purpose of this thread, to get some real world feedback.
 

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Ive used them with C6's and there is a pretty big 1st to 2nd gear drop. Too much IMHO although they are bulletproof. I ordered up a C4 kit when I started my build last year. It was a TCI unit. As soon as I received the gear set I sent it right back to TCI. Sheetmetal and TIG welded 4 pinion planetary cage that looked like a cheap flimsy piece of crap and the outer planetary gear was even worse. When I called their tech about it they said it wouldnt handle more than 300 HP.

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438" Dart Windsor, AFR 225 heads, 271/[email protected]" on 106 solid roller, 13:1 compression, Super Victor, crank trigger, 1050 Dominator, external oiling, reverse manual C4, 4000 stall, 4.10 Dana 60, Nitrous. Street '68 Cougar. 9.967 at 134 MPH! 1.44 60 ft

<font size=-1>[ This Message was edited by: mikeandnatasha on 9/6/06 2:25am ]</font>
 

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Okay, k718cougar, I understand that reasoning since you are running a stock crank.

I have not used a low gear set myself, but in theory it should work for your application. As stated by Mike, the gear drop between shifts will be greater, so you should take that into consideration but I'm betting it's still an advantage.

JPT and Pro Trans have gear sets in many ratios that are made for racing.
 

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Discussion Starter · #6 ·
I wonder how much of a gear change difference there would be between second and high gear by using the low gear kit. Engine lug/speed or not pulling like it did, etc.
 

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If you've got a high stall converter the gear change will just drop the rpm down to the stall RPM. You won't notice a problem. If it's a street style car with a low stall speed you will drop a lot of RPM on the gear change. It may woirk the motor harder until the RPM climes up agian.
 

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In the 4wd version, word is they don't last long.
Seen some people post they tried them, went back to the stock gears after they broke the aftermarket set.
 

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Discussion Starter · #9 ·
Thanks for the input. This is strickly a drag race car.
 

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On 2006-09-07 10:07, k718cougar wrote:
Thanks for the input. This is strickly a drag race car.
I'd go for it.
 

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I have a unit from PA. that is 2.92, 1.70, 1:1. I like it. My car is mostly a street car. I can run 3.25 gears in the rear. and get decent hiway rpm's and still pull nice out of the hole. the 2.92 first is the same as having 3.89's in the back if my setup. I took it to the trans shop when I got it as the shop owner wanted to see what they did. It is a welded 4 gear setup. He said he recognized it out of a GM front drive tranny with the a ford hub welded into the center. I haven't raced with it and I haven't driven it that much but so far I love it.

Tim

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351W, Ported D0OE heads,69 Shelby alum. intake, Motorsport M6250A332 cam, C4 w/low ratio gear set, TCI Street Fighter conv., 9" 3.25 t/l, SSM subframe connectors, Heidt's Granada brake kit.
In a 76 Cobra II

<font size=-1>[ This Message was edited by: cobraii351 on 9/9/06 2:48am ]</font>
 

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Discussion Starter · #12 ·
Did the trans guy say anything about longevity?
 

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Sounds the same as the TCI kit. Probably one manufacturer who builds them and then they get farmed out to different vendors. The one I saw I wouldnt put in a go kart.
 

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He made no comments as to longevity. So we'll see how it goes. but as of right now I haven't had any issues.

Tim
 

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Discussion Starter · #15 ·
Does anyone have any input regarding low gear sets from JPT, Art Carr, or JW? It would need to hold up to at least 500 HP.
 

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Try Protrans at Lancaster since i see you are in California. It was posted here a while ago that they do the gearsets in different ratio's.
 

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Discussion Starter · #17 ·
Does ProTrans have a web site or do you have the phone number? Also, I contacted PA and they said they don't have low gear sets for C-4's. Perhaps they decided not to carry them any more.
 
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