![\"\"](\"http:\/\/www.nickpisca.com\/diesel\/wp-content\/uploads\/2017\/05\/IMG_56581-300x200.jpg\")
Added an Auxiliary Overdrive<\/strong>.<\/p>\nMy van has the “bullet-proof” C6 tranny.\u00a0 While it’s a sturdy beast, it only has 3 speeds and it whines like a baby when I’m driving 65 MPH.\u00a0 So after a lot of internet searching, I found a Gearvendor auxiliary overdrive<\/a> on car-parts.com from a junkyard in Idaho.\u00a0 These units are complicated and buying them used means ensuring several parts are included (read this for more info<\/a>), but once installed on the end of the transmission, it allows for a 4th gear for the C6 tranny.\u00a0 This reduces the RPM’s to keep the van up to highway speeds, thus lessening the required fuel to drive the vehicle overall.<\/p>\n <\/p>\n Swapped out the Rear Axle.<\/strong><\/p>\n This may be the biggest way to improve MPG on these old IDI’s: Installing a more efficient rear axle.\u00a0 \u00a0Many of these old vans came with a 4.10 rear axle ratio.\u00a0 While this is an outstanding axle for towing, hauling, and other heavy duty projects, it means some very high RPM’s at highway speeds.\u00a0 If you spend most of your time commuting, road-tripping, or high-end driving, swapping the 4.10 for a lower ratio like 3.55 is highly recommended.<\/p>\n When I did this, I originally investigated prices for a transmission shop to swap out the gears in my rear axle.\u00a0 The estimate came out to $1000, which I thought was outrageous.\u00a0 After a few months, it dawned on my that I could easily just swap out the whole existing rear axle from a different E350,\u00a0which had the 3.55’s in them.\u00a0 Junkyards have these axles for reasonable prices, and aside from a standard lube change, they are pretty easy to maintain.<\/p>\n Ford Axle Code Identification<\/p><\/div>\n When hunting for an axle, you can identify it with the axle code on the sticker<\/a> in the\u00a0driver’s door of the van.\u00a0 But let’s say the sticker is gone or you have a loosey axle not connected to the parent vehicle; there should be a metal tag on the pumpkin<\/a> that has ratio information as well.<\/p>\n <\/p>\n Installed a Turbo Kit.<\/strong><\/p>\n A new turbo can wake up an NA IDI engine.\u00a0 With the same fuel quantity, the turbo compresses more air into the combustion chamber, thus providing more power.\u00a0 \u00a0While most car-guys use their improved power from a turbo to improve performance, this also can apply for people who want to improve efficiency.<\/p>\n If the driver can resist the urge to have “fun” with their turbo (like excessive acceleration, speeding, etc), that increased air-flow into the chamber means that at standard highway speeds (55-65mph) less Diesel fuel is used.\u00a0 This means overall, compared to the NA model, the driver is getting the same speed maintenance with less fuel, from the compressed oxygen.<\/p>\n However, as I can attest, having a turbo didn’t always result in better efficiency.\u00a0 The NA version of the IDI is kind of a pooch compared to the turbo, and it truly is more fun to drive with a turbo.\u00a0 But if I can resist the lead foot, I do see a few MPG better than when the Clubwagon was an NA IDI.\u00a0 While there are Banks<\/a> and “factory” turbo kits for these IDI vans, here’s the thread on how I installed my Hypermax turbo:<\/p>\n Hypermax Van Turbo Install for the 7.3 IDI in a 1988 Ford Clubwagon<\/a><\/p><\/blockquote>\n![\"Axel](\"http:\/\/fordification.com\/tech\/images\/rearendtag-ford.gif\")
<\/a>