Will this work?

[cornbinder8591]

my 1991 ext cab 4x4 with the e4od slush box has been giving me tranny troubles for the last month. after changing all the sensors I could find, still not working right. so.... just picked up a running wrecked 84' with a 6.9 and a bw4 speed, plan is yank the 7.3 with the auto still attached, deal with it later, and slide in the whole 6.9 shebang, tranny t-case, everything. I know this will eliminate alot of electrical hassles, but, I'm wondering, will the 84 drive lines work in my '91? what about the clutch pedal bracket? this is going to be my first auto-manual conversion so if somebody could give me a heads up as to any problems I might have that would be great, even if you just tell me I'm nuts. thanks.

 

[LCAM-01XA]

Doesn't really sound like an emergency, should have posted it in the regular forum. Regardless, personally no way I'd go thru the trouble of pulling an engine unless it's absolutely needed - swapping transmissions only is much easier and faster. I can tell you from now the '84 pedal assembly won't work in the '91, you need an '87-'91 pedal assembly from a manual truck. The '84 clutch master cylinder will sit crooked on the '91 firewall, so buy a new '91 one and the '84 clutch line will work with it no problem. The ideal combination would be '91 master and '84 slave both from Advance Auto Parts (they are aluminum and not plastic), and then say a '96 PSD stainless braided fluid line - expect to pay around $200 for that. The safety switch that requires you to clutch in for the starter to engage can be left out, just be aware truck can and will start in gear, also remember to pause your cruise control before shifting gears or cruise can and will redline your engine while you're clutching in/out. Transmissions will swap just fine if you either swap engines like you planned, or just strip the '91 down to bare crank and then bolt up the 6.9 flywheel to it and go from there. The 4-speed is shorter than E4OD so the '91 driveshafts will no longer fit properly, so you are on the right track about swapping transmission and transfer case and driveshafts as a complete package (obviously as long as the '84 is also extended cab). May need conversion U-joints for the axle yokes, no big deal. The '84 has the transfer case shifter coming thru the transmission tunnel cover plate, the '91 has it going thru a hole in the side of said tunnel - obviously swap the big cover plate with the transmission and case, then cover the hole in the side of the tunnel with some sheetmetal. To make the reverse lights and starter work properly you'll need the transmission harness from any 4x4 stickshift '88-'91 truck, it unplugs at the 8-wire green round connector on the inner fender under the brake master cylinder. If the '84 transfer case is a NP208 the '88-'91 manual harness will not plug into the transfer case switch so you will not have "4x4" and "low range" indicator light on the dash but the case will still shift just fine. You can splice the pigtail from the '84 harness into the newer one and get the "4x4" light back but the NP208 is incapable of triggering the "low range" light no matter what you do. If '84 transfer case is by any chance a BW1345 then both dash lights will work properly with the new harness. '91 speedometer cable and VSS will work in the '84 transfer case, just make sure you swap drive gears accordingly as different cases have different gears on their shafts.

That should about cover it. And no you're not nuts for trying this swap, and yes it will work. Been there done that

 

[cornbinder8591]

hey, thanks for the reply,man. sounds like other than a trip to the junk yard I'm covered. oh, and I only posted it under 911 because it's my only set of wheels. swapping engines because the 6.9 is a rebuild with about 10,000 on it. gives me a chance to freshen up my 7.3 maybe for a swap project Ive been kicking around (IDI model A pickup) but hey, thanks for the heads up on the electrical s and I hope you and yours have a great Christmas.

 

[LCAM-01XA]

Is your project model A or AA? Either way it sounds way cool, would be really interesting to see how you drop this big engine in the narrow engine bay and manage to keep it cool with that small radiator... Start a build thread when you get to it, we like seeing stuff like that.

If the 6.9 is fresh then by all means swap away! Personally I'd look into installing a 2nd block heater (driver side this time) while the engine is out, this can really cut down on your warmup time in case of a bad cold spell. But yeah, grab a junkyard transmission harness and you should be good for the most part, you'll need to do one wiring splice at the transmission computer harness to make the tach work again but that's easy and I'll guide you thru it when you run into it. One more thing, if you want a neutral safety switch you have to use a '89-'91 one, '87 won't work for sure and I'm not sure about the '88 models. Or just buy a new one for a '91. Also, I really would suggest that you do swap the slave cylinder to an aluminum one, the thing is literally inches away from the Y-pipe and you know how hot the exhaust can get under load. Or at the very least buy a heat-reflective "sock" to put over it, my Advance Auto slave cylinder came with one in the box already. Any other question lemme know. Merry Christmas to you as well!