1970 El Camino Th400 Transmission - TH350

1970 El Camino 4L60 Transmission Converter

Always double check your converter fitment before trying to bolt up the trans and converter as a unit. As we mentioned in the text, this check is really important if you're using a single-pattern flexplate. Dual-pattern flexplates should not be a problem, though you may consider using one that's SFI approved, especially if you plan a trip to the drag strip anytime soon.

Always double check your converter fitment before trying to bolt up the trans and converte

* Transmission crossmember needs to be moved forward from TH400 location (rearward from TH350 or Powerglide). This El Camino had multiple crossmember mounting holes from the factory, already there for different combinations. Even so, we did have to drill and tap two new holes.

* If using a single-pattern flexplate, be sure it matches the bolt pattern on your converter before installing the transmission. Dual-pattern flexplates should not be a problem, though you may consider using one that's SFI approved.

* Proper adjustment of the TV (throttle valve) cable is the most important part of this swap. The TV cable performs the functions of both transmission kickdown and line pressure. Follow the factory instructions to the letter, or call the Hughes Tech Line if you're in doubt. You can fry the transmission in no time at all, if this adjustment isn't done properly. The TV cable resembles those used on a TH350, but the 4L60 cable does a lot more. We can't over emphasize the importance of this step.

1970 El Camino 4L60 Transmission Clearance Check

Once our flexplate and other clearance issues were double checked, the new 4L60 was jacked into position.

Once our flexplate and other clearance issues were double checked, the new 4L60 was jacked

* Another key item is properly setting the vacuum modulator. Here again, Hughes supplies easy-to-follow instructions.

* Wiring for the lockup converter is simple: one 12-volt, "key-on" wire to the front, driver's side terminal of the factory plug.

Additional needs:
* Three, 1-1/4 X 5/16-inch Grade-8 bolts and locknuts for the torque converter* A 4L60/700R4 dipstick and tube* For aftermarket or Factory shifters, you'll need two metric pan bolts (longer than those supplied with the transmission).

More Numbers To Digest
The Drag Strip Results chart (right) chronicles three runs from late last year with the old TH400 transmission-using both street and BFG Comp T/A Drag Radial tires, and slightly different driving styles. Please note; the best 60-foot time from that outing was 2.02 seconds with a quarter-mile clocking of 13.053 at 106.89 mph. Not too shabby. With his new Hughes Performance 4L60 transmission, Manning ran a 1.89 60-foot time, with a best of 12.82 at 106.90 mph. During his track testing at the end of March, Manning made what most racers would consider "normal" adjustments-tire pressure, length of burnout, and launch rpm.

In conclusion, the net yields include a 60-foot improvement of .34 and a quarter-mile betterment of .225 seconds. Couple that with two days of general driving, which included in-town and freeway (stop and go and just plain go), as well as two demonstration, full-throttle blasts for some clients. At the end of that unofficial fuel test, the consumption came out to 17.8 mpg! Just imagine what constant freeway speeds would yield. We're guessing well over 20 mpg.

Seeing as how most performance-minded folks are of the curious nature, we estimate a swap like this would fall between the $1,500 to $3,000 range, depending on sources, converter selection, accessories, etc. However, please be aware of the fact that your intentions are always best served by dealing with a reputable "high-performance minded" company, for the maximum results and benefits.

This is where bad turns to good (in this case, at least). With a difference in the overall length of the tranny, our crossmember and transmission mount had to be relocated. Notice the series of holes in the frame (upper right). The factory gave us plenty of alternative locations in order to bolt everything together properly, though two new holes needed to be drilled and tapped. However, other GM models may require a bit more ingenuity.
This is where bad turns to good (in this case, at least). With a difference in the overall
Here's one of those common sense steps we're happy to pass along. Before any automatic transmission swap, it's a good idea to flush the cooler and its hard lines. This neat, pressurized can of flush was also supplied by Hughes.
Here's one of those common sense steps we're happy to pass along. Before any automatic tra
Your new driveshaft dimension is a critical measurement, too. To simulate ride height, we jacked up the rear suspension and held it in place with a tall axle stand. Next, we loaded up the old driveshaft and headed for Powertrain Industries in Garden Grove. These guys made us a brand-new unit in no time flat, with a minimum amount of balance weights to make it true.
Your new driveshaft dimension is a critical measurement, too. To simulate ride height, we

The "fickle finger of fate" is pointing to the TV cable bracket, better known as the most critical part of this swap. Hughes Performance provides completely detailed instructions for getting this cable adjusted correctly. If you need more assistance, Hughes tech reps are only a phone call away.
The "fickle finger of fate" is pointing to the TV cable bracket, better known as the most
Randy chose a B&M Pro Ratchet shifter to click through the gears with. Along with it came the necessary good looks, positive shifts, and proper mounting options desired.
Randy chose a B&M Pro Ratchet shifter to click through the gears with. Along with it came