1986 Chevy 1 Ton 5 Speed Manual Transmission Swap

Our solution came in the form of a crossmember out of a mid-'80s Chevy with a 700R4/208 combo. Since the tailhousing of the NV4500 had been slotted to clear the LoMax 205 shift rails, there is only one clocking angle for the 205. Luckily this factory crossmember drops down on the passenger side to clear the front driveshaft.

We did need to grind a bit off the back of the crossmember to clear the LoMax 205, and we installed the crossmember inside the framerails which will require complete disassembly for removal in the future, but it was still easier than fabricating a completely new piece. Moreover the crossmember hangs down lower than the 205, and allowed us to use the original skidplate with a little massaging.

From the front side you can see how the Off Road Design twin-stick shifters attach. These shifters and the modified shift rails of the LoMax 205 allow for two-wheel drive in high and low range from either the front or rear axle as well as high and low range in four-wheel drive. In addition, the shifter comes right up through the original hole in the floor for the 208 shift lever.

We did need to cut a hole for the shift tower on the NV4500. This was done by first trimming the vinyl floor mat and insulation in as small an opening as possible. Then by tracing the shift tower onto the steel floor directly above the trans we were able to cleanly cut out the opening. We will eventually find a thick rubber shift boot to keep heat, fumes, and noise out of the cab.

After taking careful measurements we ordered up a new pair of driveshafts from Denny's Driveshafts in New York. Our front driveshaft was shorter and no longer uses a constant velocity joint. We determined that dual 1350 U-joints would be sufficient in strength and still offer us enough angle. Plus since we will rarely be driving at highway speeds at full angle, the front shaft should be fine without a CV.

Out back we also replaced the shaft with a new Denny's unit. Again 1350 joints are employed and since the LoMax 205 has a solid yoke we had a slip spline built into the shaft. These shafts do not have as thick a wall as our dedicated rockcrawler's shafts, but since highway speeds will be more common than daily dirt with this truck, that was less of a priority.

The 205 received a few quarts of Lucas Synthetic 75W90 gear oil, while the NV4500 requires the more expensive and less common Castrol Syntorque. We could only find the Syntorque at a GM dealer, though a Dodge dealer should also carry it since NV4500s were also found in Dodge trucks. The special lube is required for the synchros and bearings of the transmission, and since it's a dealer item they'll ask for both an arm and a leg as payment.

These finned-aluminum PTO covers help dissipate heat which can build up after long climbs or when towing. (Note-it is not a good idea to tow with the NV4500 in the overdrive gear.) As an added bonus there is a temperature sending unit in the cover and a temp gauge in the Gear Tech kit to help keep track of the trans.

Luckily the factory brake pedal and new clutch/brake pedals simply bolt in and out with no extra holes required. However it did require complete removal of the steering column, which presents a great time to upgrade to a tilt and manual trans unit if you please. We chose neither.

We were required to drill some holes for the hydraulic-clutch master cylinder, but careful inspection revealed some embossed marks on the firewall where a factory unit would have gone. We double-checked that they would work, and then drilled them out before bolting the master cylinder in with the new pedals.

The bellhousing mount for our slave cylinder needed to be slightly modified, but we assume this was again due to the diesel engine; possibly using a thicker flywheel then the bracket was designed for. In order to keep the slave from engaging the clutch when simply bolted on, we had to shorten the pushrod about an inch.

The final step was to plumb the clutch and mount the reservoir. We found a factory GM unit that worked perfectly. All that's left is to repair the exhaust and hit the road. Check out our Web site (www.4wheeloffroad.com) for our driving reviews of going from the automatic to the five-speed manual as well as notes on mileage gains we found by being able to shift into Overdrive and let the engine relax at highway speeds.