September 2012 Nuts & Bolts Tech QuestionsPosted in How To on September 1, 2012 Comment (0)
To Cruise Again
Q After too many years parked because I broke Second gear (again) in the stock Toyota tranny and had no place to work on it, I now have a garage and some time. My ’74 FJ40 has a 0.030-over 350 Chevy with a Centerforce dual-friction clutch tied to the stock Toyota transmission and transfer case. I’m at a point in time to reengineer the transmission, and I’m thinking that I would be better off going to the 700R4 for overdrive, but I’m not certain what transfer is my better option. An SM465 is also an option in the FJ40. What do I need to do for axles? Would the stock 4.10s (maybe upgraded to a locker!) work, or would I need to change them out due to pumpkin positioning? The Toy has a spring-over axle conversion right now, but with a new frame on rolling axlehousings in the shop and a set of 4-inch aftermarket lifted springs, I›m going to drop it back down a little for stability. Basically I’m aiming for a solid streetable wheeler, not a show rig.
A Advance Adapters (www.advanceadapters.com) can help you adapt a ton of different transmissions to your transfer case. On the GM automatic side, Advance has adapters for the TH350, TH400, 700R4, 4L60, and 4L80. On the manual side, the options are just as good with SM420, SM465, NV4500, and various other non-GM gearboxes.
I like the SM465. It is a strong transmission with a good low First gear and can easily be bolted to your V-8. The SM465 does sometimes wear out and begin popping out of Third, but a rebuild usually solves this.
I wouldn’t get too caught up in the need for an overdrive. If you gear the axles right, run a big enough tire, and have a low First gear like in the SM465 for acceleration and/or off-road crawling, you can get away without an overdrive. You need to determine what rpm you want the engine to run at a certain speed, as this will help you determine what tire size, gear ratio, and transmission (overdrive or not) you need. The equation:
MPH x Final drive gear ratio x 336
RPM = ___________________________
So at 70 mph with 4.10 gears and 35-inch tires, you’ll be running approximately 2,755 rpm if your final transmission drive is 1 to 1. In an overdrive this will be lower, such as 0.80 to 1, so you’ll need to multiply 4.10 by 0.80 to get the final gear ratio. Also, remember that many tires run smaller than their sidewall markings so you need to measure actual height.
Overdrive transmissions like the NV4500 and 700R4 are great, but they have their issues as well. The NV4500 is expensive, uses expensive gear oil, and is prone to Fifth gear failure if not addressed. The 700R4 isn’t the strongest transmission either.
If it were me, I’d build it around an SM465 and 35s for good strength, simplicity, and low cost. I’d keep the stock axles and 4.10 gears and beef them up with aftermarket lockers and axleshafts as needed. I don’t think those axles will be a problem unless you want to go huge on tire size.
Eventually you could even upgrade to the Orion low-geared transfer case from Advance Adapters for the Land Cruiser and make it even more capable.
2-Wheel & Off-Road?
Q I’ve been working on my ’83 Dodge Ram D250 for about a year now. I’m 18 and this is my first truck. It is two-wheel drive, but I still plan to go wheeling in it. I know I’m going to get stuck, so I bought an old Ramsey winch from a neighbor and plan to put it on the truck. However, I can’t find a winch bumper that will fit the winch or the truck, and I don›t have the shop to build my own. Do you have any suggestions on how to mount this?
A Trail Ready Bumpers (www.trailready.com) has a base model front bumper for ’89-’93 Dodges that they say will also work on your ’83. The problem may be your winch. You didn’t mention which model Ramsey you have, but if it is an old worm-drive RE series winch, mounting will be much more difficult. You may need to find a local fabrication shop to build you a custom winch mount.
Another option would be to get a removable winch mount that goes into your receiver hitch. This allows you to recover your vehicle rearward, back where you came from. Probably not a bad idea when you’re driving a two-wheel drive.
Toys for Tires?
Q I have seen some big tires (38-40 inches and more) on Toyota axles. I am wondering how Toyota axles compare to, say, a Dana 44 or even a Dana 60. I know a Dana 60 is supposed to be the best all-around axle, but I don’t have the cash required to build one up. Is a Toyota axle worth building up (and fabbing custom mounts, etc.), or should I look into a Dana 44 or something else?
A Toyota straight axles are great in stock form and even better when you throw in the many aftermarket parts available for them. There are plenty of lockers, gear ratios, axleshafts, and heavy-duty Birfield joints to be had, but no matter what, I don’t think they are much stronger than a comparably built Dana 44. In fact, a Toyota axle and a Dana 44 are pretty comparable in strength. I have seen them both survive with 38- to 40-inch tires, but I wouldn’t recommend them for anything over 38s, even with all the high-zoot parts—and especially if you wheel hard. If you are dead set on 40-inch rubber then you probably want an axle running 35-spline or 11⁄2-inch axleshafts, such as a Dana 60 or a Corporate 14-bolt. You can also build Ford 9-inch axles to survive 40-inch tires, but they are better suited for smaller, lighter 4x4s like Jeeps and buggies.
Stacks Against You
Q I need to relocate my gas tank to accommodate some 3-inch stacks we are putting up through the back. What is the ideal way to do this without putting a fuel cell in the bed? I want to mount a bench seat back there.
A From your photo I assume you are building a Dodge half-ton and want dual stacks. I would look into a Ramcharger fuel tank that mounts behind the rear axle to replace your factory tank. Another option is to build a platform 5 or 6 inches high in the bed and run the exhaust under the platform from the passenger side so you can have dual stacks. You could then mount the bench seat onto the platform.
Nuts, I’m Confused
Q I have a ’91 3⁄4-ton Chevy truck that I’d like to build for mud bogging. I want something that works in the slop but that can also be driven on the street. I have a small car as well, so fuel economy isn’t that important from the truck. I want big tires, a big engine, and something I can hammer on off-road, especially in the mud. I recently found a deal on an 8.1L big-block from a late-model Suburban. I’ve also purchased a Ford front Dana 60 since I know the IFS has to go. Will the 8.1L work in place of my tired old TBI 454? What other upgrades do you recommend for a mud machine?
A Trucks need big power to spin big tires in the deep mud, and the 8.1L is an unsung hero in my view. A lot of people overlook them in favor of the lighter GM LS engines. It should bolt right up to your current transmission without too much drama. You probably have an 4L80 transmission behind the 454, and most of the 8.1Ls also came in front of that transmission. There were different styles of 4L80 automatics, so it depends on whether you are running the engine computer that will run the transmission or not. If so, you may need a similar-era transmission. I would go with a manual valvebody in the automatic so you can shift and choose gears accordingly; this gives you some great control. An outfit in New York, CK Performance (www.ckperformance.com), offers full manual valvebodies for these transmissions. Also, contact Pacific Fabrication (www.pacificfab.net), which has done a few custom wiring harnesses and 8.1L swaps.
For tires and suspension I would run rear leaf springs and a coil-link front suspension or leaf spring up front for your solid-axle suspension. To get big tires—say, 44-inch Boggers (Boggers are hard to beat in the mud)—I would recommend pushing the front axle slightly forward when you swap it in. This will help keep the tires out of the fenders near the front doors. You’ll want some serious lift, but I’d also trim those fenders so the tires clear at full suspension compression. If your truck came with the full-floating eight-lug Corporate 14-bolt, then you should be fine for tires up to 44. I’d look into low gears. Yukon Gear & Axle (www.yukongear.com) offers 5.38 gears for the 14-bolt, and many gear companies have that ratio for the high-pinion 60.
Building a mud truck that can still be street driven isn’t easy, but I think you’re on a good track. Every state in the nation has mud, so I feel your question is pertinent to all the readers. I’d like to give your letter this month’s Nuts, I’m Confused award. BDS Suspension (www.bds-suspension.com) will supply a traction bar kit for your truck. When you go to big power, low gearing, and huge tires, you’re very likely to see some axlewrap in your rearend, especially with a spring-over suspension. These traction bars are 1⁄8-inch-wall with large polyurethane bushings and designed to fight axlewrap. In the worst case scenario, pinion wrap can change pinion angle and cause the driveshaft joints to bind and break. Although BDS doesn’t offer a bar specifically for your 3⁄4-ton, the company’s half-ton bars should work on the frame end and may need slight modification to work on the 14-bolt. BDS offers suspension lifts for a large variety of 4x4s, from Jeeps to fullsize trucks.
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