JET Performance – 700R4 Transmission

Fighting the Slush

No, we’re not talking about wintertime in New York. We are, however, talking about a completely remanufactured and way sano 700 R-4 slush box built by JET. The 700 R-4 transmission has been quickly becoming a favorite for the auto-loving 4-wheelers in the world due to its gear ranges. The 700 R-4 sports a low first gear of 3.06:1 which comes in handy for rock crawling, steep hill climbs and towing. It also comes stock with a 4th gear overdrive for highway cruising, but it does have its flaws. Aside from its low range and overdrive characteristics, the stock tranny does have problems with overheating, premature failure and a lack of strength in the material department.

With the stock, yet potentially strapping 700 R-4 under our rig, we were faced with the fact that it definitely needed a rebuild. Our choices were finding a local shop that had experience with rebuilding and strengthening 700 R-4’s or finding a company that had a strong reputation doing so. Clear the stage for the boys at JET Technologies in Huntington Beach, California. As a preface, JET, Jones Electronic Technologies, started out as a fuel delivery company dealing specifically with electronics and carburetors. With their growing success, JET owner Bryant Seller took notice of Premier Performance who was known for building high quality transmissions. Adding a reputable transmission builder to their entourage would only add to their success. They have since become the leaders in several markets including the transmission market, distributors, chips for vehicle computers, carburetors, air filters, and much more.

After calling JET we were asked an assortment of questions to help them build the transmission for OUR rig. Tire size, gear ratios, engine specs and a description of how we used our Blazer was given before they could actually start building our new tranny. The rebuild itself consists of more than 40 modifications including extra clutches, the stock servo replaced by a Corvette servo for improved shift points, a special boost valve, and a pre- programmed valve body for firmer shifting and 30% more overdrive than stock. After Jet completes the rebuild, it’s off to the transmission dyno for a full-blown test before it ever leaves the building. Wow! There’s nothing like having a test drive before it actually gets bolted into the vehicle.

Next is our installation guide. See how you can bolt in your new 700 R-4 and what we thought of it after testing. 


Step 1
Based on the difficulty of this installation, we had to line up the use of an overhead lift and the aid of an ASE Master technician. Because this transmission has electronic components, we first disconnected the battery, as we didn’t want to risk any possibility of damaging the shift solenoid when it is disconnected as the removal process starts. The next critical step before going any further is to carefully remove what is called the TV Cable (throttle valve cable) from the side of the throttle body or carburetor. This is a must because once the vehicle is above your head it would be extremely difficult to do so later.

Step 2
With that completed and the truck up in the air, we started removing the front and rear drive shafts. Care must be taken when doing this because they will need to be installed the same way they were removed. Do this by making small marks on the yokes with a grease pencil, so you know where the u-joints lined up. This will keep you from getting driveline vibrations after reinstalling them. Another tip is to use tape or a u-joint cap keeper so that the caps do not fall off and run the risk of losing the small needle bearings.

Step 3
Next we drained the fluid from the transmission. We had the luxury of using a tool called a Vacula. This allowed us to siphon all of the old fluid out of the pan, through the fill tube, without actually removing the oil pan. After all of the fluid was out, we removed the cooler lines from the passenger side of the transmission and the starter, taking care not to lose the starter shims.

Step 4
Subsequently came the removal of the transmission/transfer case cross member. We used a pneumatic transmission jack to support both the tranny and t-case while we removed all of the bolts that held it in place. Once all of the bell-housing bolts were removed, we took our time lowering the tranny and t-case as a unit. This all went pretty smooth but we definitely recommend having two people during this process.

Step 5
Once out from under the truck, we removed the bolts that hold the transmission and transfer case together and carefully split the two apart from one another. Before mating the new tranny to the transfer case, a new o-ring, which is provided with the new transmission from Jet, was installed. Torque all bolts to manufacturer spec when reinstalling.

Step 6
Once mated together, the process is reversed and the new transmission is lifted back up into place and bolted to the back of the motor. Before re-attaching the transmission cooler lines, remember to flush the lines thoroughly as well as the cooler. In our case we will be substituting the stock cooler for an external cooler with fan assist (look for a separate review on this product soon). We chose to do this because of how we use the truck and the nature of 700 R-4 transmissions running hot to begin with. Remember that heat kills an automatic transmission more than anything else.

Step 7
After the cooler lines are hooked up and the drive shafts are in place, it’s time to re-attach the TV cable to the throttle body. The adjustment for this is critical, and you must follow the provided instructions to do it correctly. After double- and triple- checking everything, it’s time to fill the new trans with fluid. Ours took nine quarts all together and we suggest that you add the oil slowly and check it periodically so that you don’t overfill it. After this, we finished by re-attaching our battery cables.

I must be perfectly honest; Other than going back to make one small adjustment to the TV cable to correct a small shift problem, this Jet transmission was perfect out of the box. With 3,000 plus miles gone by, the transmission has performed perfectly. During our testing we noted more precise shifts, crisper shifts and a better overall feel to the transmission. Our new 700 R-4 tranny is now set up to handle the rigors of off-road, heavier towing and more abusive driving without worry.

Jet also recommended that after the first 600 miles, we drain the fluid and install a new filter.

With the 700 R-4 proving itself in military applications, desert race trucks and hundreds of 4×4’s, it makes it easy to see why so many four wheelers are choosing this transmission to be the one to swap into their rigs.

JET Performance Products
Web Site:
JET Performance Products
17491 Apex Circle
Huntington Beach, CA 92647
Voice: 714-848-5515
Fax: 714-847-6290


Description Notes Rating
Ease of Install If you have the right equipment, the installation is easy and straightforward, but time consuming.
Ease of Use N/A N/A
Performance Transmission shifts are firm and crisp with zero slippage even under heavy load.
Durability The transmission is built for increased durability and long life.
Appearance The transmission comes completely clean and painted. As far as a transmission goes it looks great.
Drivability The transmission took a few weeks to break in and relax. Initially the transmission shifted very hard but soon broke in to firm, yet crisp shifts.
Comfort N/A N/A
Price in comparison to related products Comparable in price to other hi-performance, rebuilt 700R4 transmissions from reputable shops
Tools Required Preferably you’ll need an auto-lift, a transmission jack, an air ratchet, various sockets and wrenches. This can be done without a lift and a large floor jack but it’s considerably more difficult.
Editors Notes Expect an abrupt 1-2 shift from the transmission due to the Corvette servo and the shift kit. After a few weeks the transmission will loosen up a bit but still has hard shifts from first to second. Overall the transmission is an excellent addition to our truck and should last a very long time, even in the off-road rigors…TS

About Rick Webster

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