1985 GMC Jimmy Transmission Swap - B&M 700R4 Transmission

Before

B&M Helps Our Jimmy Get Off the Trailer It was a sad phone call. Our friend and freelance photographer Alisa "Bean" Morrow called us and said she needed a tow. After fighting a good fight, her '85 GMC Jimmy's high-mileage 700-R4 transmission decided that Third gear and Overdrive required too much effort, and it simply gave up. Rather than take our advice, she listened to another friend who used the most used and abused words in the automotive repair world, "Oh, I know a guy who can fix that." After six weeks and a Jimmy that still needed a transmission, she finally realized that she needed more help than "a guy who can fix that" could provide. Enter B&M Racing and a magazine guy eager to help.

After

B&M Racing knows transmissions-it's what they do-so the choice to unbolt our broken hunk of junk and install a tried-and-true transmission was a no-brainer. It also helps that B&M doesn't just sell you a rebuilt factory transmission with a shift kit with the pretense that it's a performance tranny. No, their transmissions are built with many brand-new performance parts and don't leave the factory until they're dyno tested to ensure optimum performance. Complete with Corvette 2-4 servo assembly, recalibrated valvebody, new bands and friction plates, and a shift kit designed to provide crisp 1-2 shifts, the new B&M transmissions are ready to rock right out of the box. All we needed was a new Tork Master torque converter, adjustable B&M throttle valve kick-down cable, and electronic torque converter lock-up controller, also from B&M.

For some of you, the thought of converting a 4WD fullsize Jimmy into a two-wheel-drive truck is heresy, and we understand that viewpoint. But, for this owner's mostly freeway driving and for better fuel mileage from the thirsty Quadrajet-equipped 350ci V-8, we opted to install a very street-friendly B&M 700-R4 with overdrive. If you've heard transmission horror stories in the past and those stories have scared you away from doing a swap yourself, this article will hopefully shed some light onto the truth about transmissions. With a little mechanical know-how and basic handtools, you too can resurrect your truck back onto the street and off the trailer.

It was a sad sight when we arrived at Bean's house, the broken-down Jimmy was parked in the driveway with no clue that B&M Racing had come to its rescue by way of a new 700-R4 transmission.
It was a sad sight when we arrived at Bean's house, the broken-down Jimmy was parked in th
Unfortunately, "a guy who can fix that" took the original tranny out of the truck, so we can't show you those steps, but here is a quick rundown: unbolt the exhaust crossover tubing, unbolt the starter and flexplate cover, along with the three torque converter bolts on the flexplate, remove the driveshaft, disconnect the fluid lines, remove the speedo cable, dipstick, T/V cable, and electronic connector on the driver side. Make sure you have the tranny supported with a large jack and a piece of wood to disperse the weight under the fluid pan and remove the transmission housing bolts from the block and slowly pull the transmission free.
Unfortunately, "a guy who can fix that" took the original tranny out of the truck, so we c
Opening the box from B&M immediately impressed us. Only a company who takes pride in their product goes to such an extent to ensure it gets to you undamaged. There's a 700-R4 under there, we promise.
Opening the box from B&M immediately impressed us. Only a company who takes pride in their

Our first step was to add a quart of B&M's Trick Shift performance transmission fluid to the B&M Tork Master torque converter (sold separately). We chose the Tork Master 2000 for its low cost, solid construction, and street friendly 1,900-2,100 rpm stall.
Our first step was to add a quart of B&M's Trick Shift performance transmission fluid to t
Moving to the transmission itself, we lubricated the torque converter pump drive with some Trick Shift fluid and then slid the Tork Master converter onto the pump drive. We made sure to slide the converter (while rotating) all the way onto the pump drive until we heard the second "click", indicating it was completely engaged.
Moving to the transmission itself, we lubricated the torque converter pump drive with some
An important step was to double-check the converter's engagement by measuring the distance of the torque converter's drive lug face from the edge of the bellhousing. To do this, we used a straight edge and tape measure to ensure there was at least 1-inch inside the front edge of the bellhousing.
An important step was to double-check the converter's engagement by measuring the distance