Thought you may find this interesting.


http://www.corvette-guru.com/modules...d=9464&forum=1
http://www.corvette-guru.com/modules...d=9557&forum=1
http://www.corvette-guru.com/modules...d=9611&forum=1
http://www.corvette-guru.com/modules...d=9658&forum=1

 

These have been around for a few months now, the price is around $900, and the ratios are the same as the Ford AOD-E/4R70W. First is 2.84:1, second is 1.55:1, third stays 1.00:1, and fourth is 0.70:1. This seems silly to me, but the 60E guys will find arguments for it. For the rest of us, just convert to a well-built 200-4R if you don't love the 700's gear ratios. Having a 200-4R built to hold 620 ft-lbs costs the exact same as having a 700R-4 built to hold 620 ft-lbs. And the 200 is lighter and has less hassles to live with once it's in.

 

The price for the gearset is $1150 plus shipping. If you are buying a trans from PATC, they give credit back for the GM 5 pinion gearset they are removing, thus a net cost of $950 . There has been confusion over the price, but $1150 is what they cost to buy outright, today.

For a c4 vette, a 2004r is not easily done. Vette does not have a crossmember for the trans. It is supported by a "C" beam that rigidly bolts the trans to the fixed rear.
Because the 2004r is cast with a 1 piece bellhousing/case/tailshaft, it is not possible to put one in the vette without major chassis mods, or mods to the case of the trans.

Anyhow, options are a good thing, and this is an option for a ton of GM cars, that was not possible before this summer.

The guy writing the build up plans to provide dragstrip testing on 2 identical transmissions (except for the gear ratio change).
It will be interesting to see the results on his combination.

 

An even better, and cheaper, idea is to figure out how to get the stupid 700R-4 to go from first, to first and overdrive, then to second, then third, then overdrive. This would do an even better job of keeping the engine in the powerband, and keep the low first gear that is the main advantage of this trans over all others. The ratios would then go: 3.059/2.129/1.625/1.000/0.696. I suppose we could then call it a 700R-5 :-)

 

I know you could easily use the converter clutch to do that sort of thing. 1st, lock converter, 2nd and unlock converter, lock converter, 3rd and unlock converter, lock converter. I have heard there are a number of people that just lock it and keep it locked from either 2nd or 3rd.

 

The hype on the new gear ratio set is pretty much that. This gear ratio and other gear ratio sets have been tried before, 2.66 was one of them. I have found for all practical purposes that a good "matched" torque converter will give you what you need at a less cost and less headaches. Yes, they have their place, but for the average street vehicle, no. Locking and unlocking the torque converter between gears was what GM tried in the early 700R4's, and you see how well that worked.

 

Dana,
Are you saying that there were gains, but not enough to justify the cost, or that there were minimal, if any gains?

 

There were slight gains, but not enough to justify the cost as you said. Many years ago we compared the 2004R with the 700R4 both using the 27 spline input shaft so that we could use the same torque converter for the comparison test. A couple of other shops did the same comparison test. The vehicles ran from low 12's to low 13's in the quarter mile. The 2004R was on average a mile per hour faster and a tenth quickerover the 700R4. This was very little in gain, and we know some of it had to be the lighter weight of the 2004R gear train and not the 2.74 first gear ratio. I guess if you had a very peaky motor in terms of horsepower, then that would make for a bigger gain going to a closer ratio spread gear set. With the late motors having a broad horsepower and torque range, (a 383 ci. motor) this closer ratio gear set would seem to be, a waste of money.