with Bill Johnston
Tweaking the Grip
The Stalker project started with 31″ tires, so we lowered the gear ratio in the differentials to make up for any loss in power that the larger tires caused. The freshly rebuilt motor took full advantage of the gearing as it pushed the little 4×4 through the interstate traffic with ease. But although the engine seemed to thrive now at higher rpm’s, we wanted to bring the stress on the motor down a little and maybe prolong this newfound energy. This installment will show how we dropped the rpm’s a little when in 5th gear (highway driving) and then gave the clutch a bit more ‘gription’.
The first thing we had to do was get the transmission out of the vehicle. This is pretty straight forward, here is a helpful tip for those that find it tight when trying to drop the tranny. Trim the bracket (shelf) that the rear transmission mount sits on. This can give you at least another 1/2″ of working space. It doesn’t seem like much, but it sure helps when trying to get the transmission past both the crossmember and the pressure plate at the same time. Also, don’t forget to unplug the sensor wires that plug in at the firewall. These are easy to forget and usually cause a quick slap to the forehead after realizing what the tranny was hanging from as you try to wiggle it out of the chassis. Here we see two Samurai transmissions. The dirty one just came out of the Stalker, the clean one is freshly rebuilt with all new bearings, synchros and seals. Besides the new parts and the caked on oil, there is a major difference between them. The original (dirty) transmission had a 5th gear ratio of 0.865:1. This was new for the 1988.5 model year and it allowed higher revs for the highway giving the little motor a little more strength on the highway. The ‘new’ trans we have prepared is an 1987 model that has a 5th gear ratio of 0.795:1. It doesn’t seem like much of a difference at first, but with the added power this motor has shown, it can more than make up for the loss in RPMs up top. Since one of our goals was to hit triple digits, it will also be the difference between running 100mph at 6039 RPMs – or running 100mph at only 5551 RPMs. It also brings a 70mph highway cruising speed down below 4K RPMs. Click on the tables left and right to see the whole thing. Now that we have the revs nailed down, we need to control it a little better than just using a stock clutch, as they tend to be a little wishy-washy when you drop the clutch… The stock clutch does its job well with stock parts, or when you are running low transfer case gears that will take most of the abuse when offroad. But we need something that will take more abuse. You can see the stepped style flywheel on the right. This should be resurfaced whenever you replace a clutch, but this one was fresh when we put it in last month and it doesn’t show any signs of wear yet. Here is the answer to our prayers. You are looking at a Petroworks Heavy Duty Clutch and Pressure Plate. It looks like most of the clutches out there until you flip it over. The pressure plate side has the organic material one would expect to see, but the flywheel side is much different. The eight feramic (feros and ceramic) pucks you see instead of more organic material are designed to grab without fade. Some racing clutches out there have the feramic pucks on both sides to ensure a solid lock-up during a hard launch at the dragstrip. This clutch is designed to take the abuse that would fry a normal component yet be street friendly for normal traffic. On the left you can se a stock unit next to the PW component. On the right you can see that there is also a difference in the pressure plates. The one on the far right is the Petroworks component while the one on the near right is stock. The ‘fingers’ are larger, stronger and the overall assembly show a higher quality than stock. It is installed the same as a stock unit would be, just remember to remove the spline tool before trying to shove the transmission back into place… or it could get very frustrating until you figured it out. we moved the switches (wires/plugs that are on the top left side of the trans) over to the fresh trans and then slid it into place. One of the things that usually doesn’t come with a rebuild kit is the rubber plug that fills the timing cover hole on the drivers side of the transmission. (Timing Cover?) Yup, there are markings on the flywheel that allow you to set the timing at the front of the transmission if you prefer. The rubber plug on the fresh trans was eaten away from years of oil spills, so a quick call to Petroworks got us a replacement for a couple of bucks. The shifter is the last part to install. After checking the alignment bolt at the front of the shifter opening, we slid the shifter into place. Her you can see the ‘new style’ poly shifter sheet. Strange name for a bushing, but that’s what they call it. This is the yellow part you can see by clicking on the picture for a close-up. The stock shifter sheet is usually green. Broken alignment bolts and worn out shifter sheets are usually the cause of a jammed shifter that won’t come out of gear. Positive traction and a more reasonable top end RPM were the main goals for this month. We hit both points right on target with help from Petroworks. Next month we will add the Weber 3800 DGAS carb, supplied by JFE, and a trick new intake manifold – both prepared by Kevin ‘Sarge’ Lafferty. Source:
Petroworks Off-Road Products 111 W. Aviation Rd. Fallbrook, CA 92028 Tel: (800) 952-8915 Orders (760) 731-9434 Tech Fax: (760) 723-7596 Email: email@example.com firstname.lastname@example.org