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Discussion Starter · #1 ·
Gentlemen:

I am fairly new to the 3800 scene, but I am a HD Diesel mechanic with quite a bit of experience and I am ready to start tinkering in the automotive world. I did my homework and research and decided a SC 3.8 is the perfect platform for me. I have had some exerience with NA 3.8s but alot of this is new to me. Heres a basic setup:
Stock/All Rebuilt 00 Grand Prix GTP Daytona 500 with 4T65E-HD trans (Also Rebuilt)

I have seen what these cars can do and plan on building this one up in the high 300 if not low 400 whp range (eventually-durability with power is the key). I have heard that these transmissions are the weak point on these platorms as well as with the LS4's. Ive seen some upgrades done to valve bodies and Torque Conv's on LS4's but nothing gives any details.

Any good ideas on how to "Beef Up" this transmission to handle those power ranges?

Main Idea: Tighter shifting, wider power range, longer life span, quicker throttle response, and o yea...3:29 gears.

Any thoughts on the 3:29 gears would be helpful as well. Im not very good with FWD Transmissions, or rather dont have much experience with them, but I believe there is two ways to change the final drive of the trans to 3:29. Best way? Better way? Is it worth it?

Thanks guys, this is my first post on here, just to give you a reference of how new I am to this engine platform.
 

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I like the 3.69 gear ratio. Fuel Economy is affected very little. As far as tranny upgrades I would talk to Dave over at Tripple Edge.
 

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I am itching to go with 3.69's in my Park Ave Ultra. The Lexus GS300's are 3.92 geared 3.0L I6's, and the V8's are 4.0L 3.27 geared. Buick has a 3.8L engine and a supercharger and are a lame 2.93. Pathetic.....

In the heavy Park Ave with SC or not it SHOULD have 3.69's.....

Easy to swap gears, just change the internal gears on the chain link. 37/33 is stock (we have 3.29's already) and 3.29/1.121212 is 2.93. And 3.29 with 35/35 is 3.29 and 3.29 with 33/37's is 3.69. So the trans drive is underdriven with the 3.69's and overdriven with the 2.93's.

When I priced the parts a while back it was around $300-$400, but takes time and $ to pull it and install it. Not hard to install IIRC. Not for everyday joe's to do though, I would not consider a "bolt on"

Brian can tune them for you, if not I can show him how. I don't think HPTuners can do it, will have to look for it.
 

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Rainin' on my parade :)
I went with a 35/35 sprockets and the Buick diff with 2.93.
My goal was mileage though,not acceleration.
Seemed to work well enough,with basically no mods her L67 would roast the tires if I stomped it below 40mph.

I had an issue with tuning,but it was before I found out that the Buicks had the different ratio diff.
TCII has no issues tuning it,though he did need to update the .dat file as my particular calibration was not recognized.
 

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I know mpg would suffer some with 3.69's, but a more optimized cam would help that too. Stock cam i would say sucks for anything more than a NA 3800. Especially a SC 3800....

I drove a 05 GT GP back in 05 that had the 3.29's stock on a L32 and it was a ball, it really ran nice.

On my GS400, everyone said the GS300 with the 3.92's got nearly the same mpg as the V8 GS400 with 3.27's. I went with the GS400.... I have got best of 31.x with a 300 HP V8.... I can't complain. I have NEVER got worse than 18 mpg yet and that was in the cold last week where I let it idle a lot when I wasn't driving.

Just looking at simple torque calculations (torque * first gear * final gear) just switching from 2.93's to 3.69's in the 3800 SC stock brings 600 lb-ft torque to the equation. It makes a big diff. I have a spreadsheet where I put in a lot of numbers like power, torque, tire size, gear, trans gear and come up with a normalized torque. Basically if you have a Duramax with 600 lb-ft it levels the playing field for tire size when comparing to a 3800 for instance. Oh a 3800 with 3.69's over 2.93's would cruise at 65 mph at 3000 rpm in 3rd and 2411 rpm in OD. Up from 1700 rpm. My Lexus cruises rpms like that, at 75. No issues really, my Fleetwood with factory 3.42's cruises at 2200 rpm at 75 mph. No effort at all with a 5000 lb barge and 29 in tall tires factory.

I call it Launch Normalized torque. Top dog of what I have in the sheet so far, 2006 Workhorse RV chassis with a 8100 big block, 5.63 gears and Allison trans with a 3.1 first gear. Tops out over 10,000 lb-ft of launch torque.... Out of the 60 vehicles I have in so far, the top ones are Duramax's (I don't have in Dodge/Ford diesels yet) and the bottom are 3800 L67 and L36.


Rainin' on my parade :)
I went with a 35/35 sprockets and the Buick diff with 2.93.
My goal was mileage though,not acceleration.
Seemed to work well enough,with basically no mods her L67 would roast the tires if I stomped it below 40mph.

I had an issue with tuning,but it was before I found out that the Buicks had the different ratio diff.
TCII has no issues tuning it,though he did need to update the .dat file as my particular calibration was not recognized.
 

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After I exploded the dual trans chain setup with 2.93 a couple years ago, I had the single chain 3.29 setup installed. Around my local area, I find that this combination works very well with my stock cam and 1.9 to 1 rockers.
E85 at 50% gives about 16mpg.

Driving on the expressway is really where the change is noted. If I drive at 70mph, the rpm difference changes the fuel economy somewhat. On longer trips, I drive at about 62mph and keep the engine no more than 2K rpms.

I have BF goodrich G-force tires. They are very sticky. I have not hit nitrous since the trans chain snapped. I believe n0dih is right about using 3.69 gears with a cam though. I am pretty satisfied overall with the E85 mix. The input shaft on my trans really needs the upgrade.
 

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Discussion Starter · #7 ·
So what I'm getting is go to triple edge for some performance parts and go with 33/37 gears to get the 3.69 ratio. I checked out triple edge already and I'm very impressed with thirty website. I'm not sure how far i want to go with the transmission yet. am assuming my best route to safely building the car would be to start by building the transmission, intake and exhaust, and getting a tuner/pcm capable of traking a few channels as well as
the normal programming functions. Then get into the cam, headers, pulleY, charger, and all that other good stuff.
 

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I like the idea of the 3.69 gears to take some of the strain off of the transmission.
It sounds like you are on track for a good build.
Are you going to move up the HP ladder in small increments or are you going to go with a specific 'recipe' with all the components at once?
 

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With the right gears a 100hp engine has as much power as a 1000hp engine and crap gears.

So case in point:

1999 Lexus GS 300 0-60 mph 7.5 Quarter mile 15.5, 3.92 gears, 3.357 first.

1992 Pontiac Bonneville SSEi 0-60 mph 8.0 Quarter mile 15.9, 2.93 gears, 2.92 first

2000 Pontiac Bonneville SSEi 0-60 mph 7.4 Quarter mile 15.6, 2.93 gears, 2.92 first

2004 Pontiac Bonneville GXP (Northstar V8) 0-60 mph 6.8 Quarter Mile 15.2, 3.11 gears, 2.96 first

Look at the pattern, the Lexus GS300 is 3700 lbs, and with a 225hp 6 cyl, no blower, is slightly slower than a similar weight Bonnie SSEi. And even the GXP Bonnie with the 275 hp Cadillac Northstar isn't much faster than the base 6 cyl. Add in a GS400 or GS430 and 0-60 is 5.7 sec and 14.1 quarter.

GM would rather throw inches at a power problem then try to gear it right and match the cam to the gears.
 

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Shop around, these are common off the shelf parts. Don't pay extra to a "speed shop" for no reason if you don't have to.

Transmission parts USA Automatic transmission parts is one place that might have them, they are excellent on price and service, used them on some 4L60E parts in the past.

I know someone who works at a dealer, maybe he can help.


So what I'm getting is go to triple edge for some performance parts and go with 33/37 gears to get the 3.69 ratio. I checked out triple edge already and I'm very impressed with thirty website. I'm not sure how far i want to go with the transmission yet. am assuming my best route to safely building the car would be to start by building the transmission, intake and exhaust, and getting a tuner/pcm capable of traking a few channels as well as
the normal programming functions. Then get into the cam, headers, pulleY, charger, and all that other good stuff.
 

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Discussion Starter · #11 ·
Well, here is a few responses and questions to what you guys have been posting.
gtx500hp - What ERPM were you seeing when running 70? I am not a reckless driver, but I can not drive under 75 or 70 on the highway. Most the places I drive to and from have a speed limit of 70 anywaw, also what would be considered too high of an RPM to cruise at? and What would be my best option for gearing then? I want more power for sure but power is not the only focus of my build, i need functionality as well and reducing my cruise speed by 15mph with a faster car is not my definition of a functionality updgrade.
1997MontanaGS - My idea is to, at first make small steps in HP focusing more on durability and longevity, upgrading things that hinder the stock engine like intake, exhaust, transmission, mod pulleys, PCM and tuner, fuel pressure regulator (heard lots of horror stories resulting in burnt GTPs due to a bad FPR). Once the little stuff is done and all the "Weaknesses" have been addressed, then I will start making HP jumps, mainly a smaller pulley and intercooler, ignition, valvetrain, headers, Cam, injectors maybe. Cam should probably come with the gearing change from what im hearing.
Im not totally sure exactly how far I want to go with this car. I want it to be fast, but not impractical. This is all going to take a bit of time as well, I have a nice stock pile of disposable cash for this project right now, probably about 2 grand at this point to put towards upgrades, possibly more. (I know the tranny will most likely cost about half of that as I will probably not risk doing that work on my own, tho I think i could) My budget after that $ is gone will be significantly less, thus durability and doing it right the first time is my priority.
nOdih - I see what your saying, and totally agree with you, but (repeating myself) being able to cruise at 70-75mph and staying in a safe ERPM range is giong to be key when I consider gearing change. Any ideas on a good gear set/ratio to achieve the power increase but not sacrifice safety when driving on the High way? Also, Cam size ideas for this final drive ratio?

Thanks a ton guys! i have never had this type of helpful response from any forums I have been on, auto related or not. You guys know what your talking about and are making it easy for me to overcome the learning curve I am up against being a HD Diesel mechanic and working on a SC V6. Im learning alot very quickly.
 

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Discussion Starter · #12 ·
Forgot to add in my last post, Suspension will be done as well before any serious HP gains are made, most likely SLP replacements, from what I have heard there suspension parts are top notch, Also, how does everyone feel about leaving the transmission gears alone and changing out the Diff with a larger final drive? too much stress still on the trans?
 

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Discussion Starter · #13 ·
Anyone have anything to say about Thrasher Engineered Performance? Their website seems very comprehensive and they have tech articles on just about everything. They have been answering alot of questions for me with their articles, Saves me some typing time and you guys some answering time...
 

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Personally, I miss being able to run my car at 70 at around 200-2100 rpms. I got 28mpg at that speed.(no E85 mix).

Now I drive at 62 mph at 2000-2100 with 3.29 gearing. So, I would guess that to run at 70mph, I would be turning 2400 rpm. There is definitely a los of fuel economy when traveling at 70mph now. However, there is a nice transition between gears around my area where speed is limited to 50mph.
I would definitely not want 3.69 gearing with a daily driver. Again, I get 15.6 mpg average by computer, and I have the biggest set of 18 inch tires I can fit. (had to cut rear fenderwell lips too)

The consideration has to be if you are going to put a cam in the car and not care about fuel economy. Montana 97 and I0dh are very seasoned guys. Probably the best for a cammed car that revs to 7k. My 421S.D. ran a 4.56 on the street, the engine would spin to 7200rpm. Cheers KEV
 

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This cam would do pretty well for 3.29's to 3.69's.

COMP Cams 76-802-9 Xtreme Energy 264 HR15 Hydraulic Roller Cam for GM 3800 : Amazon.com : Automotive

I am sure there are lots more, but this is a quick find.

GM likes cams that have 190 degrees duration @ 0.050. So the cruise rpm range is very very low. Remember that this is a stock NA cam in the SC engines, GM didn't even do due dlligence and make a proper supercharger cam. My 455 Pontiac was good with old Cam Dynamics 284H ([email protected] .480 lift) and cruise rpm at 70 was close to 3000 rpm (no OD in the THM350). My dream was to find a 421 or 428 Pontiac. Let alone a SD421!!!

If you must run a stock cam with 3.69's, probably retarding it 4 degrees would help get the power band up a little higher.

I often drive my SC 3800 in 3rd around town under 55 or so when I need the power.
 

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Discussion Starter · #16 ·
So, with 3.29 gears and a mild cam I'm looking at 15 mpg? I wouldn't think the gear change would affect it that much? Is that a big lobe your running GTX? I think 329 gears and a mild cam would do the trick for me. I'm mainly wanting to be able to put a hurt on the 5.0s and SSs, but still maintain decent mpg.
 

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My 3800 gets 16 mpg with 2.93's in hard core city. My Lexus V8 isn't near as bad. I would think in the city would improve some depending on how aggressive you drive.

Hurting a SS or 5.0 with a 3800 is a tall order. Assuming a modern 5.0 or modern SS Camaro, that is going to take some serious mods and $$.



So, with 3.29 gears and a mild cam I'm looking at 15 mpg? I wouldn't think the gear change would affect it that much? Is that a big lobe your running GTX? I think 329 gears and a mild cam would do the trick for me. I'm mainly wanting to be able to put a hurt on the 5.0s and SSs, but still maintain decent mpg.
 

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The cam im my GTX is stock. However, I am running 1.9 to 1 rockers which help quite a bit. I know that if I were to tear the engine apart, I would heavily port the heads, add heavy valve springs and a somewhat nasty blower cam. Gas milage would drop to about 12-13 I would guess.

The 421S.D in the past was pretty built. It was bored .120 over, had o-ringed block, 12.5 to 1 pistons, with a Mickey Thompson cross-ram and duel 660 holleys. Car was a 68 firebird with no heater or windshield wipers.Never lost a race on the street in those days...fun part was that Chicago cops never really bothered me...30 years ago..cheers KEV
 

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I guess I'll throw in my $0.02.....Keep the 2.93 gearing.

I have been in modded 3800 cars with 2.93, 3.29, and 3.69 gearing. Especially if you plan on doing highway speeds most of the time I'd think you'd be crazy to change out the 2.93 gears. In the even that you need to upgrade to a 7/8" chain give Triple Edge Performance a call and talk with Dave....he'll tell you that the 2.93 gearing seems to last the longest and occurs the least amount of chain stretch. These engines have plenty of torque to get the bigger cars moving...especially if they have a few performance parts on it.

You have to ask yourself how important it is to shave off that 1/10th of a second in the 1/4 mile all while sacrificing mpg the whole time. I will always run 2.93 in these cars.

1997 GTP - 1.9, P-log, 3.4, 3" off road downpipe - 22- - never put on the dyno
1998 GTP Turbo - ST2, Cartuning Turbo kit - 23-33mpg - 350whp/512wtq
1999 GTP (E85) - SIX, TOG's, GenV, 2.8 pulley - 18- - 330whp/401wtq

All with 2.93 gearing.
 

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So, with 3.29 gears and a mild cam I'm looking at 15 mpg? I wouldn't think the gear change would affect it that much? Is that a big lobe your running GTX? I think 329 gears and a mild cam would do the trick for me. I'm mainly wanting to be able to put a hurt on the 5.0s and SSs, but still maintain decent mpg.
The poor 5.0 liters are still the center of attention when it comes to a platform people want to chase down............;)
 
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