This post is premature. It will require patience for a final conclusion. If you get too excited and can’t wait I recommend a daily regimen of Scotch, Whiskey, Vodka or like liquor. In a pinch you can resort to wine.

Thanks to Grip (Anthony) I’ll be taking the leap to a 3.27 carrier and thanks to Rudy it’ll work. Changing from a 3.07 to 3.27 is a small step to say the least. I took the time to approximate the speed differences at gear changes. (255/50/16 drag radials)

Here's my calculated mph at 6100 with the 3.07 (not exact but close)
1 rst 42.9
2 nd 70.3
3 rd 109.2
4 th 154.00
5 th 185.50

Here's my calculated mph at 6100 with the 3.27 (not exact but close)
1 rst 40.3
2 nd 66
3 rd 102.5
4 th 144.6
5 th 174.2

Here's my calculated mph at 6400 with the 3.27 (not exact but close)
1 rst 42.3
2 nd 69.3
3 rd 107.1
4 th 151.7
5 th 182.7

The shift points at 6100 put me before peak torque after the gear change. 6400 puts me at peak torque after the gear change. Average hp after the 6400 gear change is +15. I don’t expect the mph in the ¼ to change at all from the 3.27. If I’m correct, the ET will drop .1 just from the torque multiplication at launch and for the first 60’ or so. The raised rev limit should gain me another .1. Don’t you just love speculation? The carrier is in the mail and if the Ground Control suspension comes out in the next week or so I’ll consolidate the installations and get the pain over with in one swoop.

I used a 6400 TCU once on the dyno and once at the roundy round track. I didn’t see a lean issue so hopefully I’m good. If not I’ll go the regulator and un regulated fuel filter route. What say you?

All criticism, doom sayers, fan bois, etc. are welcome to opine on the raised rev limit and my data.

Les

 

Les.
I am so interested in the same setup. I missed the opportunity to buy grip grip. It was sold to late bigkid Jim and I hate to ask is it for sale now which is rude. Les I am in need of information here to purchase, how much, and installation. Thanks.

 

The carriers are inexpensive. You can find them for $150 and up. I've heard the 2004's have different axel clips so buy 2005 and up. The yolk has to be removed from you old carrier and put on the 3.27 carrier. Then you need a TCU tune. Our cars have 2 limiters. The ECU limiter for the engine and TCU for the transmission. So your tuner will need to raise the ECU limit to where you want it. The TCU will also have to be raised or the car will keep changing gears at the stock limit regardless of the ECU limit. All added up it's expensive. In my case I have a Wavetrac already installed. So both have to be dismantled, the 3.07 ring gear removed from the Wavetrac, the 3.27 ring gear removed from the donor, 3.27 installed on the Wavetrac and the assembly
installed in the donor carrier. Then we cross our fingers for no surprises.

Les

 

I am wanting to change out my 3.27 for a 3.07.
I would rather have a 2.84.
Since I have a 6speed it would make the shifting points/mph a lot better. And lower my 78mph cruise rpm lower.
A 3.07 drops 240 rpm @ 78 mph

 

wow. i wish i would have bought grip grips. I dont have a Wavetrac. I was waiting to do all at the same time.

 

les how do you think your valve train is going to react to a raised limit of 6500? weak springs could have a catastrophic affect at that rpm

 

The Mercedes diesel use a 3.46

 

Steve! Good to hear from you. The ECU is set at 6500 but the TCU will be at 6400 and that's where it'll shift. Currently in my car is an Evotech TCU with a raised limit and I've been banging off the limiter with no ill affects, so far. My thinking goes like this. The valves in our engines are tiny and on the light side so that's a plus. I read the MB forums and it seems quite a few over there are red lining at 6800. I haven't seen a "blew the motor" story from the raised limit. Then I start thinking about how many cars I've owned that lasted over 10 years. If it blows after a while I'll find a nice Porsche or CL65, but I think the engine will endure despite the extra rpms. If anyone knows of a blow engine (3.2) with a raised limit I'd like to know about it. I could be playing with fire. Perhaps I've convinced myself otherwise erroneously.

Steve, since you know the guys at Buckhead could you ask them their opinion?

Les

 

be happy to ask. my thinking is the springs are built based on a 5800 rpm limit. raising the limit to 6100 is done on a regular basis but it has to have an impact on the strength of the springs. raising it to 6500 or 6800 is putting them in dangerous territory and with a zero clearance motor drop a valve and you wipe out the top end possibly killing the cams as well.

swapping the rear is fine but i would tread lightly on the valve train. just my .02 that and 5 bucks gets you a latte at starbucks!

 

Now I'm confused. My car redlines at 6100 stock. Did when new and still does unless I flip the switch to raise it. Where did you come up with 5800?

Les

 

my bad. been away from the car to long. same thought pattern applies though

 

Now for your road racing and my autocross what do you think this would do with a little taller of a tire? say 295 30 19 or 285 35 19? looking at your math, which holy crap thats cool, these gears being taller should yield a little more torque and the tcu tune paired with the raised rpm, say 6400, would hold 2nd till about 70? any idea how much more torque would be after the swap?

 

I used this gear calculator. John Maher Racing » GEAR RATIO CALCULATOR
After plugging in both your tire sizes you'll see how small each tire change is from stock. Tenths of a mph using the 6100 rev limit.
The stock shift points are good from a torque standpoint. It lands my car within single digits of the torque peak and with the 6400 gear change I land at the peak. The big difference is in the hp at each gear change. I retrieved my hp and torque numbers at each data point from a video of my last dyno. The information on the dyno screen lags a bit but it's as close as I could get. With the 6100 shift and either gear ratio the revs fall to 3719, 3927, 4326 and 5063. With the 3.27 they fall to 3905, 4117, 4539 and 5314. Those 2xx rpms on my car are 15 hp. more from post shift to redline average. If my schooling had made math this much fun and useful, I'd have been much more studious.

Les

 

You will like the change Les... I am still awaiting a gear change as well. All good points but you are only hitting those high rpms for seconds at the most and I am confident your valve springs will hold up just fine. Hopefully we will hear something on our up and coming gear change as well.....or I may spend the money on the house instead...lol.

 

Do both! I mean, were between 50 and death. Spend it while you got it or give it away. Well, I only use that reasoning for dubious purchases but it changes my way of rationalizing expensive car parts.

Les

 

i could always use a sponsor

 

Carrier is on my workbench and the TCU is ordered and paid for.

Les

 

I like your logic.