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I can't help it. I have to know. Was thinking of strapping one of these to my steering column. Had one on my '69 Dodge Coronet back in my high school days and it was super cool. Loved it. Even had a B&M floor shifter for it but that won't happen on my van. Just the tach.
I've had one, not added it yet, the engine was replaced and I never got around to adding it, been focused on everything else breaking every day I think its fixed, can't recall which wire to tap, not seen any tach wires.
I've watched a few videos. Just like Manicmechanic said, 3 wires. I saw a few setups on vintage F150's and Chevy trucks and they all looked damned good.
I've been adding air bags on my van, not had time to do the tach, it was on my 73, without over drive it helped me keep the RPM reasonable on the HWY, I put a vacuum gauge in my dash on this one tho, so WOT zeros it, so obviously MPG decreases, no real reason for a tach.
My C6 is fitted with a Gear Vendors OD unit so the RPM's are pretty relaxed at 65-70. It does start to get busy again at 75. With the OD turned off the engine gets busy by 55-60. I'm guessing that's about 2,800 rpm?
OMG you are lucky, instead of overdrive, I have a stupid high gear ratio, rear is a 3.08, would like 3.73 to tow over the mountain here, I rarely do the highway.I literally have had to rebuild everything on this van, the rear axle and fuel pumps are all that hasn't been pulled and rebuilt, so I want to monitor it all but next, my wheelchair lift needs rebuilt, hydraulic leak, cost more than the lift did years ago, so another interrupt of what I want to add next. I have a Equos Sunpro tach, knowing my luck it may not work. Do you know your rear gear ratio, at 65MPH mine isn't screaming, my 73 302 topped out around 80MPH, had 3.25 gears, the engine was screaming, pretty sure any more would blow it up, tho the MPG was near the same as this 300 in the city, so much for EFI superiority, reason I want a tach is to see if its revving high.
My van is an '88 E350 with the 460 and C6. 4.11 gears. So without the OD, the engine was quite busy by 65 mph. I remember when I went to go see the van and looked underneath and saw the Gear Vendors unit, I knew I was going to buy it! However, it only gets around 10 mpg in mixed city and highway while cruising no more than 65. It feels very relaxed at that speed. I like to believe that if I did all highway I might get 12 mpg but that's just a theory. The van does have a high top camper with a full camper build that is probably pushing my E350 into the 8k lbs. weight range. The 460 easily keeps up in the flats. But as soon as there is a long grade, I really need to push far into that accelerator to maintain speed and I can almost see the fuel gauge move!!!
Last edited by OCBlue88; May 14, 2026 at 10:01 AM.
My friend had a custom build van, he used an ambulance in the build, nickname was Cloudy, had a cloud pattern welded on the front windows, gullwing doors, pulled a 24 foot camper, to events, was the first person I knew personally to have a gearvender unit, he built the 460 in his van, had large dual tanks under it for traveling. I fear he has passed away, he was building custom vans through the 70's making it to truckin's, that van had a cloud mural on it at one time, believe he had digital gauges in it, neither him nor Bonehead got more than 12 MPG, Bonehead swapped out and put a 97 ambulance interior, dash, firewall, and drive line in his giving him a dually with a 7.3 turbo diesel, increasing towing and mileage, but was a massive customization, no digital photo of that one, just a 35mm I took at the 2005 nationals. A diesel is the only option to get a decent MPG, I had a 99 E350 ext with the 5.4 tuned and best trip mileage was going to Florida, all down hill 17 MPG, usually over the mountains in Tennessee I got 15 MPG rolling 70-75MPH, 3.55 gears kept it down, I did a lot of driving middle to east TN with that van.
I need to go through my wiring manual for my 89 and find the tach wire, if there is one, a new 4.9 has to get better than 11 MPG in the city.
Gear Vendors still operating out of San Diego. Very responsive to emails. Will rebuild your OD for $1,800 if one needed that done. There is a function in their OD where you turn it on/off manually in between your gears, acting like a gear splitter. So if you had a 3-speed you'd end up with 6 effective ratios. Mine doesn't have a manual switch installed and I don't think I want to be pushing a button on/off while driving. I could have sworn that the E150/250's fitted with the 5.0 V8 had OD in their transmissions way back in '86. I remember going to see a mint '88 E250 with the 5.0 and OD transmission. It had an "O" and "D" overlaid on top of each other on the transmission gear selector. But on any other motor, the non-OD C6 was used up until '90?
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