By: John Nutter - 7/2000
Project Do It Yourself: Drive Train
|A Chevy 4.3 fits well under a CJ7 hood. There is 5" between the fan and radiator and 4" between the distributor and firewall. The remote oil filter is normally bolted to the inner fender and is OEM equipment on 4wd S-10s with a 4.3.|
|A long V-8 J-truck T-18 input shaft and retainer and their Ford counter parts. The Ford input retainer has already been machined down to Chevy size.|
|The Jeep T-18 ready to be assembled with the Ford input shaft and bearing retainer.|
|The drivetrain hanging over the frame. The flash didn't work on this photo.|
|Side view of DIY shows off the extra clearance under the new skid plate.|
|Another view of the new skid plate. Moving the drivetrain forward and up allowed a higher skid plate with decent angles on both driveshafts.|
|The floor needed a little trimming to accomodate the new drive train position.|
I had a hard time tearing my Jeep down. The old 258 had really worked well. I was also looking ahead to the Moab Easter Jeep Safari in less than three months and not sure if I could complete an engine swap along with everything else I had planned. I loved my 258 and the idea of putting in a non Jeep engine didn't sit well. On the other hand, I had just picked up a Chevy 4.3 V6 with TBI. It was lighter, shorter, more powerful and fuel injected. After a couple of days contemplation and hours spent with a tape measure, good sense won out and I made the descion to go ahead with the swap.
I had been gathering parts for the swap for the 4.3 swap since the day I picked it up. An old Camaro 4 speed bellhousing was salvaged from underneath my Willys Wagon. An '87 Chevy full sized van driver's side exhaust manifold and a flywheel from a '91 S-10 with a 4.3 and 5 speed were purchased from John's Auto Parts in Blaine Mn. Novak Adapters supplied motor mounts and a pilot bushing for Ford T-18 input shaft used with a Chevy engine. Dave Jacobs helped me find a cheap Ford T-18. Dave had already given me a long input T-18 from a Cherokee Chief a while ago. A 3 core radiator was purchased and I had the outlets swapped and an extra 5/8" fitting for the heater return line installed as well. The rest of the parts came from various full sized Jeeps that had been salvaged at my house over the years.
Transmission work was the first order of business. I had a Dana 20 with 3.15:1 low range gears from Tera Mfg and I was very happy with my current 6 cyliner J-truck T-18, except for the length. This transmission has a 1" thick adapter plate on the front and is uses the T-14/T-15 type bellhousing which is about 2 1/2" longer than a Chevy or later CJ bellhousing. A T-18 with a Ford input shaft and Dana 20 adapter is the shortest possible granny low transmission combination, so this is what I built.
The Ford input shaft is fairly easy to swap into a Jeep T-18 with the long input shaft. The top cover, input bearing retainer and adapter plate were removed first. The snap ring holding the front bearing onto the input shaft was removed next and the front bearing was removed. These snap rings are very stiff and require a special pliers. It is possible to remove them with a regular snap ring pliers, but it is very difficult. The rear bearing had no snap ring on the output shaft and was pulled out using the outer retaining ring. With the bearings gone, the two halves of the upper shaft could be sepparated and taken out through the top of the transmission. There are several needle bearings that fall out when the shafts are sepparated, but they are easily retreived from the bottom of the transmission. For re-assembley, the needle bearings were installed into the Ford input shaft using grease to hold them in place. The rest of the re-assembley was the reverse order of disassembley. The one note here is that the synchro from the Ford T-18 wasn't exactly the same as the synchro from the Jeep T-18. I ended up using the Ford synchro and I now have a problem with the tranny coming out of 4th gear. The solution to this problem is another re-build using all Ford gears with the Jeep output shaft, in a Jeep case to match my adapter.
Novak Adapters has published the information on how to adapt a Ford tranmission to a Chevy engine with no adapters for as long as I can remember. The info is available in their print catalog and online. Novak's method works equally well with most 3,4 and 5 speeds from 1976 and newer Jeep CJs. The basic idea is to machine down the input bearing retainer to the same size as used on a Chevy passenger car, drill a couple of holes in the bellhousing and use a special pilot bushing available from Novak. The pilot bushing is very reasonably priced and shouldn't ruin anyone's budget. The upper two bolt holes on most Jeep and Ford transmissions are nearly in the right spot to match the upper holes on the Chevy bellhousing, a few minutes with a file makes them match. The lower holes will have to be drilled into the Chevy bellhousing. Instead of tapping the holes, I inserted bolts from the inside. When using a Jeep T-18, one of the lower bolt holes ends up under the clutch release arm. Minor grinding makes a flat spot for this bolt head. The other lower hole ends up in the far corner, just inboard of the original hole in the bellhousing and right in the middle of the webbing that ties the bellhousing together. This bolt head sits on the webbing, but can still turn. I used JB weld to secure the bolt and had no problem with it turning as I tightened the nut. A Ford clutch disc, Chevy clutch cover and throwout bearing and the pilot bushing from Novak comleted the adaptation.
Motor Mounts and Skid Plate
With the adaptation complete, the engine, transmission and a spare Dana 20 transfercase were connected together and hung over the frame. Determining the final position for these pieces was very time consuming. Placement was tested with the suspension at running height and full droop. The tub and grille were also installed and removed several times before the final position was determined. The goal was to get a skidplate that was flat across from frame rail to frame rail and equal length driveshafts if possible with a rear driveshaft angle that was no worse than before and good engine placement. It would be a bonus to get the front driveshaft up higher since it had been a rock magnet in it's previous location. Eventually I settled on a position that left the bottom of the skid plate about 1/2" below the bottom of the frame rails.
It was time to work on the motor mounts and skidplate once the placement of the drive train had been determined. I started with a set of motor mounts from Novak Adapters . These consisted of two brackets that bolt to the engine and two that bolt to the frame, plus polyurethane bushings similar to body mount bushings. The engine brackets worked out perfectly, but the frame brackets were too short for the desired engine placement. The frame brackets were simple angles with gussets, so it was no problem making taller brackets. By coincidence, the brackets lined up with the original motor mount holes in the frame.
The resulting drivetrain placement has worked out well. The engine is about as high as it can be without hitting the hood. There is 5" of clearance between the fan and the radiator and 4" of clearance between the distributor and fire wall. The tub required some sheetmetal trimming because the shift tower on the T-18 came out just ahead of the original opening. Some pounding on the underside of the tub created the neccesary clearance for the transfer case, with only a small loss in space available in the passenger wheel well. The rear driveshaft angle stayed the same as it had been with the longer and lower drive train, while I was able to raise the front driveshaft angle signficantly. I was also able to rotate the front pinion up about four degrees for even more clearance under the front drive shaft.