33 Coupe Transmission 1        8/22/03

I ordered my transmission from Bowtie Overdrives and picked it up the other day. After talking to Steve, the owner of Bowtie (which is a very nice guy), and going over all my options (they sell three different kinds of overdrive transmissions), I decided on the 4L80E which is the strongest overdrive that GM makes. That's the good news, but the bad news is that it cost's the most out of them all. And it's also the heaviest of them all too. I had to unload it with my hoist because I couldn't pick it up (220 lbs.) Now this transmission uses a computer to make it operate which is why it's so expensive. I cut a piece of wood the length of my wheel dolly and set the trans on it so I could move it whenever I need too. The overall length is 4 1/2" longer than a TH-400 (Turbo 400) which means it mounts in a different location (on the tail-shaft). If you remember from the chassis section, I already made a new cross-member and relocated it for this transmission using a mock-up case that I borrowed. Now this SHOULD bolt right up when the times comes.



This shot shows the front of the transmission which has some ears sticking out on both sides. I'll be removing these before I install it to give me a little more clearance. The rib down the center will have to go as well because of clearance problems. The two red caps are covering the place where the cooling lines will go. The gear ratio on this unit is 1st. 2.48:1,  2nd. 1.57:1,  3rd. 1:1,  4th. .75:1 (overdrive). The first three gears are almost the same as a Turbo 400 along with it's strength. While going 65mph in overdrive, the engine should only turn 2450 RPM's which isn't to bad considering I have a rear gear of 4.56. 



Here is the torque converter which is 11" in diameter (that's 2" smaller than the stock one and it weights less too). The stall speed is 2600 RPM so I hope it works like I want it too. If I don't like it, Bowtie said they would let me have any other stall speed that I wanted for FREE, "one time only". All I would have to do is drain the old one, box it back up and return it for any stall I could dream up. Now this is something I didn't expect. How many companies would do this for there customers? Not many is my first guess. I'll have to see how this one works and go from there. 

This converter is a lockup style converter which means it has a clutch in it. When your in high gear (overdrive), this clutch engages to give you better fuel economy and reduce engine RPM. In order for all this to happen, the transmission has to kick-in some hydraulics that are controlled by the computer and how much throttle your giving it at the time. Let's take a look at the computer system I'll be using which will explain what I mean. 



The transmission is controlled by Compushift made by HGM. This is one sweet system we have here. Now I like computers so when I heard that the Compushift system was programmable, I just had to try it. Let's take a closer look at this system.


1  2  3  4  5  6  7  8  9  10  11  12  13  14  15