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1985 GMC Jimmy Transmission Swap - Go From This, To This!

D-I-Y Transmission Install

Dan Ward
Oct 1, 2010
Photographers: Dan Ward, Brandan Gillogly, Alisa Morrow
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.
Photo 2/29   |   Before
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.
Photo 3/29   |   After
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.
This was the first transmission I've installed and besides the 4WD to 2WD issues (like new tranny mount, crossmember relocation, the welded crossover exhaust tube, and buying a new driveshaft), it was a straightforward process. Thankfully, we didn't have a hard deadline, so working on it for a full weekend wasn't a big deal and like all wrenching, several trips to the parts and hardware stores were required, (but when aren't they required). Now the truck has a crisp 1-2 shift and strongly holds each gear, helping get the big Jimmy down the highway. The best parts of this install are seeing the Jimmy driving under its own power, keeping a cool truck on the road, and knowing we did the work ourselves.
Time Spent Working: A Weekend
Degree Of Difficulty: Moderate
(mechanical ability and ability to follow instructions are key)
Tools Needed:
Large hydraulic jack, jack stands, assorted wrenches and sockets, flare nut wrenches, screwdriver, torque wrench, rubber mallet, wide piece of wood for tranny support
Parts Used:
B&M 700-R4 transmission 117101 $1,686.81
B&M Tork Master 2000 rpm torque converter 70420 $244.65
B&M Lockup control 70244 $186.13
B&M T/V kickdown cable 70242 $39.95
B&M Trick Shift transmission fluid $59.99 (case of 12 quarts)
Used speedometer gear adapter $29.99
Miscellaneous Grade 8 bolts for tranny housing $11.00
Transmission mount from '85 Chevy Camaro $12.99
Driveline's Inc. custom one-piece driveshaft $300.00
Total: $2,571.51
(All B&M prices from Bmracing.com, all others vary by location and do not include tax, shipping, or installation)


Drivelines, Inc.
Mission Viejo, CA 92691