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  • TDC - Technical Questions & Answers - April 2004

TDC - Technical Questions & Answers - April 2004

Questions regarding Chevy trucks and maintenance

Bruce Caldwell
Apr 1, 2004
The Goodbye Gear
I removed the gutless 305 in my '84 Chevy El Camino and replaced it with a blueprinted 383 stroker motor. The engine is supposed to put out at least 425 honest horsepower. I believe that because I've already destroyed the original automatic transmission. It cost about $2,000 to rectify that problem, but now the transmission is up to handling the engine. My concern is the rearend: The 7.5-inch 10-bolt rearend lasted longer than the transmission, but now that I won't be losing power in the transmission, I worry that the rearend will be the next horsepower victim. I'd like to take the truck to the track to see how fast it really is, but I don't want to embarrass myself by scattering the rearend all over the starting line.
Can I do anything to improve my existing rearend, or do I need to install a 12-bolt or a Ford 9-inch rearend? Since I've already spent so much, is there any Chevy rearend that I can just bolt in to my truck? Could I just install bigger gears, such as 3.73:1 or 4.10:1, and an Eaton posi-traction unit?
Fred Calavaro Jr., Zanesville, Ohio
A: You're right about your chances of saying goodbye to your present rearend at the dragstrip. The stock 7.5-inch ring gear and 26-spline axles aren't up to the task of handling 425 hp; that's almost three times what the original 305 produced. A good step up would be a 7-5/8-inch ring gear, 28-spline axles, and the Eaton posi unit. This setup is definitely stronger than what you have, but it might not have a long life, either, depending on how hard you drop the hammer on that 383. Either a 12-bolt GM rearend or a 9-inch Ford setup for your truck would work well. There are lots of aftermarket companies, such as Currie Enterprises (, that can fix you up with a rearend strong enough to handle any situation.
Both rearends can handle dragstrip abuse, but if you plan on doing a lot of racing, we'd give the nod to the 9-inch. A big plus for the 9-inch is the way the axles are retained. Four bolts per axle flange secure the axles, and the axles can slide out if necessary. The bearings are pressed on with retainer plates that bolt to the axlehousing flanges. This means that if you break an axle, the axle retainer will prevent the axle from leaving the rearend.
Since 12-bolt rearends use a C-clip axle retention system, if something breaks, there goes the axle, wheel, and tire. This can cause body damage or a sudden drop to the pavement. There are C-clip elimination kits for 12-bolt rearends, but we'd still go with the 9-inch for racing.
A downside to a new 9-inch or 12-bolt setup is cost. A new 'housing fitted with all new parts, including a Detroit Locker, a 3.73 (12-bolt) or 3.70 (9-inch), and 30-spline (12-bolt) or 33-spline (9-inch) axles will cost somewhere in the $2,000 to $2,500 neighborhood. A lot of peace of mind comes with one of these purpose-built rearends, but it sounds like you'd prefer to spend less. There is a high-performance bolt-in rearend that you may be able to find. The late-model GM 8.5-inch rearend that came in Buick Grand Nationals and Hurst Oldsmobiles of the '83 to '88 vintage are a natural for El Caminos. All of these vehicles are so-called "G" bodies, so the rearend widths and mounting points are identical. You can get aftermarket performance gearsets and posi units for them.
Supply and demand is a potential problem, however. Buick Grand Nationals and Hurst Oldsmobiles weren't high-production vehicles, and their value as performance cars isn't a secret. It might be worth some Internet shopping or consulting a local wrecking yard that's tied into a national parts locating service to see if you could find one of these rearends at a reasonable price.
Trans Plans
I have an '82 Chevy Suburban two-wheel drive that I love to death - and have almost used to death. The truck has more than 300,000 miles on it and is still going strong. Over the years I've owned it, I've made several improvements. Now I have the chance to upgrade the original automatic transmission. I have a couple questions regarding the transmission plans. I can get either a 4L60-E from a low-mileage '94 GMC 1/2-ton pickup or a 4L60 from a '90 Chevy 1/2-ton with about twice the mileage; the cost is the same for both units. Can I run the 4L60-E without a computer? Is mileage a factor in how much transmission use I have left without doing any work to it? Both trannys are at a truck wrecking yard and have a minimal guarantee. Are there things I can check before I buy to see if they're OK? Thanks for your help in keeping my old Suburban on the road.
Eric Hansen, via e-mail
A: Given that the price is the same, we'd opt for the newer, lower-mileage 4L60-E transmission. The 4L60 is the non-electronic version of the transmission, which is probably why it appeals to you. These manual units were available up until 1993. You need the computer that came with the truck, or a valid substitute, in order to use the electronic version in your older Suburban.
Aftermarket companies quickly recognized the popularity of the electronic overdrive automatics. They saw the great potential for retrofitting these units in street rods, classic cars, and older trucks. One company that makes swap kits for these transmissions is Jet Performance Products ( The company offers a wiring harness and controller for carbureted trucks (PN 750222).
Wrecking-yard guarantees or warranties tend to be very basic. Ask for details (in writing if possible) before you put too much faith in such a guarantee. Often, these guarantees are of the free-replacement variety. If you get the transmission home, install it, and find out it's junk, you can take it out of your truck, haul it back to the wrecking yard, and the company will gladly give you another one. Then you get to go home and go through the drill again.
We once installed three engines under one of these guarantees. The wrecking yard people were great about taking back the first two duds, but we got pretty tired of yanking engines in and out of our truck. A guarantee backed by paperwork showing that the engine or transmission was run on a test stand would be much more reassuring. Modern wrecking yards don't want to waste your time, or theirs, so it's a pretty safe bet that they've made some type of general inspection before offering it for sale. At minimum, we would pull out the dipstick and look at and smell the transmission fluid. You don't want to see really dark or burned fluid, nor do you want to smell anything acrid or burned. If the yard is willing to drop the pan and let you look, that would be even better. You don't want to find a lot of debris or sludge in the pan; that can be a sign of worn friction plates. You definitely don't want to see metallic particles, either. Little pieces of metal usually come from grinding up big pieces of metal.
Change Is Good
I'm trying to be more conscientious about upkeep and maintenance on my '99 Tahoe, but I'm concerned that my local independent repair shop is trying to sell me services I don't really need. Repairs can be very expensive on late-model trucks, but the shop's not giving away the maintenance services, either. I recently had new brakes installed all around at about 60,000 miles on the odometer. The shop tried to sell me on cleaning the fuel injectors, changing the brake fluid (I've never even heard of this), changing the coolant, repacking the wheel bearings, changing the differential gear oil, and flushing the engine and switching to synthetic oil. The shop said these things will pay off in the long run, but it just seemed like a big bill in the short run. I did go for packing the wheel bearings, since the crew was already working on that part of the truck. Is all this stuff necessary, or is the shop just trying to increase business?
Nick Buhl, Charleston, South Carolina
A: The shop sounds a little aggressive, but at least it didn't suggest changing the air in your tires. The shop isn't totally out of line with the services it tried to sell you. Everything it recommended is important, but it's a question of when and how often.
A thorough, professional injector cleaning as opposed to a "cleaner-in-a-can" isn't a bad idea at 60,000 miles, but how well your truck is running should figure into when you have the injectors cleaned. It makes reasonable sense to repack the wheel bearings while the crew has the wheels off for the brake job. Just make sure the shop didn't charge you the amount of shop time it would take if things weren't already apart for the brake service.
Changing the brake fluid sounds like busy work, but it actually isn't a bad idea every three or four years. Brake fluid can absorb moisture over time and you live in a pretty humid climate. The biggest reason to flush out the old brake fluid on modern vehicles is the antilock braking system. ABS problems are far more expensive than anything brake-related on non-ABS vehicles.
Coolant companies have always recommended flushing and changing coolant on a regular basis, but few people follow that advice. The problem with modern vehicles is the increased use of aluminum components in the cooling system. The concern is corrosion and electrolysis, which is more likely when the anti-corrosion properties of the coolant wear out. Regular coolant changes can help maintain those anti-corrosion properties.
You should keep tabs on the differential oil level, but unless you see signs of leakage, it shouldn't be a big problem. Synthetic oil is a fine product; most people who use it, swear by it. Those people tend to be owners of high-performance vehicles. But, there's nothing wrong with top-quality regular oil as long as it's changed on a consistent basis. The question is whether it's worth the added trouble and expense to flush out the old oil and replace it with synthetic oil. That's a decision only you can make.
Photo 2/3   |   tdc the Goodbye Gear
Photo 3/3   |   tdc change Is Good
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