WHY- 4T65e HD / 3800SC. what am I missing ? a 3800SC is capable of over 6000 RPM and a 4t65e that comes with it only uses a 2.93 final" gear". WHY would it not be beneficial ( for racing,) the use a 3.70 or 4.11 instead ( Again, IF they were available)???? I am thinking of getting the chain and gears for the 3.29 out of a different cat/van. wouldn't the small cube, short stroke engine gain big time in the 1/4 mile ?? the car is really Only "using" the 1st 2 Gears !
All 4T65-E HD's got a 3.29 ratio differential. But most came with 37/33 chain sprockets which yields the common 2.93 overall final drive.
You can do 35/35 chain sprockets to get to 3.29 or 33/37 chain sprockets to get to 3.69 overall; but those are your only choices with a factory 3.29 HD differential.
The 3800 SC makes great low and mid-range torque, so it doesn't really need crazy gearing to perform well.
------------------ More is more. Less is not enough. Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com
WHY- 4T65e HD / 3800SC. what am I missing ? a 3800SC is capable of over 6000 RPM and a 4t65e that comes with it only uses a 2.93 final" gear". WHY would it not be beneficial ( for racing,) the use a 3.70 or 4.11 instead ( Again, IF they were available)???? I am thinking of getting the chain and gears for the 3.29 out of a different cat/van. wouldn't the small cube, short stroke engine gain big time in the 1/4 mile ?? the car is really Only "using" the 1st 2 Gears !
If you are seeking 1/4 mile performance and wish to change the chain and sprockets, its not an easy job for someone that has never done this job. Short description: To access the sprockets, the rear cover, valve body (I believe that it has four ball checks too) , the pump shaft and the main drive shaft need to be removed before you can fit a new chain and sprocket. You must know which bolts to remove and which ones stay put. Then everything must be assembled exactly as it was removed. Its an easy job for a transmission guy but for many hobbyists unfamiliar with the process it can be difficult.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
And, no one has been able to answer me on this yet....just what are the tangible gains in 0 to 60, 1/8 or even 1/4 mile times? I too am thinking about doing this swap..... but i just haven't seen any hard data on IF it is worth doing.....
Lou, you're a better mechanic than most of us. When I did a 4T60e years back I had to buy the instruction video. Its an involved process but you follow it step by step and pay attention you can get the job done. As for the question above on how making the FDR lower will improve 1/4 mile times. That's best answered on the 3800pro,com forum but Pennocks member darkhorizon (Scott) ran a 9.87 1/4 mile time with his turbo 3800 and maybe he will tell you what trans FDR he used. He hasn't posted since he broke the all time record for the fastest Fiero but his info is still in the registry. Maybe someone who knows Scott will let us know where he might be..
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Okay, went through some of the 3800 product web sites. Found this at the Intense web site under Tech Info/ Tips and Tricks.....
"How will steeper gear ratios affect my car? Generally speaking, steeper gear ratios will improve your acceleration and E.T., while reducing your fuel economy and trap speeds. In round numbers, each gear step (from 2.93:1 to 3.29:1 for example) will reduce your quarter mile E.T. by about a tenth of a second and your trap speed by about 1.0 MPH. Your engine speed (RPM) will increase by about 13% at any given vehicle speed and your gas mileage will be reduced by about 7%. Changing from 2.93:1 to 3.69:1 gears will approximately double all the effects listed in this paragraph."
I not using currently using 4T65. However when I had a 3800sc tied to a 4T60e with the same fine final drive gears found in the HD. (but without the larger shafts and standard right housing) I was able to improve performance by editing the shift maps in the PCM bin. I was able to edit the shift points corresponding to TPS, and MPH points. I also did this to match with the tire sizes. Shifts to 4th no earlier than 47 MPH. You can also edit the TCC lock up points. Since then, I have had to use my car as a daily driver and I am using a newer 3800n/a. The shift points are a little early for this engine, but are working great for the MPGs.
