How To Make A 700r4 Work Without A Computer

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HOT ROD Rescue: Lockup a 700-R4 Torque Converter Without a Computer

Pam Jacoby'southward 700-R4 Trans Won't Lockup the Torque Converter. We're Gonna Fix Information technology.

The Combo

Guys don't believe a girl tin can own a automobile like this." — Pam Jacoby

"Ever since I was 16, I've been into cars and hot rods. I'grand definitely an oddball in what's still mainly a man's world," relates Pam Jacoby. "Guys are surprised that a girl owns and drives quondam American iron. When I'thousand with my boyfriend, they tend to ignore me and start talking to him almost my cars!"

Pam's latest find: a beautiful 1932 Ford Model A Roadster she discovered online at Autotrader Classics (Classics.Autotrader.com). Its Chevrolet 350 Ram Jet crate motor is shifted past a 700-R4 trans with a ii,500-rpm stall-speed converter.

A Chevy Ram Jet 350 transfers torque through a 700-R4 automatic overdrive to a 3.55:1-geared open 9-inch Ford rearend.

The Problem

The 700-R4's ii,500-rpm-stall converter wouldn't lock up, resulting in excessively high rpm and reduced mileage at freeway speeds.

Although the rod was spirited around town, highway driving was a pain. "On the freeway, it tach'd also high because the torque converter wouldn't lock up," Jacoby complained. In fact, many retrofit hot rod 700-R4s are delivered without a functional torque converter clutch (TCC) lockup circuit, ostensibly to forbid a modded engine and trans from "hunting" (jumping in and out of lockup) during everyday stop-and-become driving. As locking up the converter effectually boondocks tin can brand a car feel lazy, non-lockup proponents maintain you'll run across better initial response at throttle tip-in. The non-lockup's downside is prolonged steady-country cruising with higher-than-stock converter stall speeds generates excessive heat, shortening the transmission's life expectancy. And since Fourth gear sustained cruise rpm is higher with a non-lockup converter, gas mileage decreases, partially negating the benefits of overdrive.

The 700-R4 shifts Jacoby's Chevrolet Performance Ram Jet 350 crate engine. Rated at 351 hp and 403 lb-ft, it resembles old Rochester mechanical fuel injection, but has modernistic GM MEFI 4 ECU-controlled port EFI. A MEFI 4 tin't control 700-R4 TCC lock-upwards.

The Diagnosis

The Rollings Automotive coiffure (clockwise, from top left): Son Ron, nephew Mark, and Dad/owner Norm got a "lock" on the trouble.

The Roadster went over to a slap-up all-purpose repair shop, Rollings Automotive. It repairs just about any car, early or tardily, old-school or high-tech. Rollings' full range of services includes complete auto-trans rebuilding. Inspection revealed all parts needed for lockup were present inside the trans—they just weren't connected to annihilation.

Several switches, connectors, and a TCC solenoid are all that's needed to get a 700-R4 TCC to lock up without a computer.

The Fix

For an onetime motorcar similar Jacoby's, 12-volt power for the TCC circuit is supplied through the ignition switch'due south accompaniment terminal. With the motorcar running, the commonly open (NO), dash-mounted manual switch toggled to the "On" position, and the trans in Fourth (overdrive) gear, the NO valvebody pressure switch sees hydraulic force per unit area and closes (self-grounds), completing the circuit through ISO relay terminals 86 and 85. This energizes the relay, assuasive loftier-side current to flow through terminals 30 and 87 to the TCC clutch solenoid valve, and finally to an external Ground at an extension housing commodities. The TCC solenoid engages, locking up the converter. When the trans downshifts to Third gear, the pressure switch opens, interrupting flow through the relay to unlock the TCC solenoid. Alternatively, the driver tin unlock the converter at whatsoever fourth dimension past toggling the nuance switch to the "Off" position. The lettered callouts stand for to the side by side legend box.

The lettered callouts reference the callouts in the diagram and the two photos immediately following this diagram. The callout numbers reference the numbered photos at the end of this story.

A] Ignition switch (numbered photos 0103)

B] Manual nuance switch (numbered photos 0406)

C] Trans case connectors (numbered photos 0709)

D] Valvebody harness

Due east] Pressure switch (numbered photos 1012)

F] TCC clutch solenoid valve (numbered photo 13)

G] ISO relay (numbered photograph 14]

H] TCC solenoid Basis wire on instance

Accessible by dropping the trans pan and removing the filter, these are the major internal parts and wiring harness needed for TCC lockup. Depending on who congenital your "not-lockup hot rod" 700-R4, any or all of these may or may not be nowadays. The callouts reference the Legend in the "How It Works" diagram.

This is how Rollings wires the 700-R4 TCC circuit on the driver side of the case for manual lockup. Major connections include the external Weatherpack connector, the ISO relay, and TCC solenoid Footing. Although the relay here mounts conveniently to an existing threaded case hole, if at that place's a clearance issue, it could be relocated anywhere. The callouts reference the Legend in the "How It Works" diagram above.

Rollings commonly prefers manual TCC lockup command via a dash-mounted switch; the converter locks up in Fourth gear merely when the driver desires lockup. In Rollings' stance, manual lockup offers the all-time of both worlds: not-lockup performance for in-town driving; lockup in Fourth (overdrive) gear for sustained, steady-land cruising. Any 30-amp-rated pushbutton, paddle, or toggle switch can be used. Supply 12 volts to the switch's input side from either a fuse box accompaniment-tap or (as wired on Jacoby's rod) from the ignition switch accompaniment terminal.

On the output side, Rollings wires the switch through a standard ISO relay. The low-current, ordinarily open (NO) side of the relay supplies current to the Fourth gear pressure level switch on the valvebody inside the instance, which closes in 4th gear and allows the high-electric current side of the relay to engage the TCC solenoid. The relay is there to protect the pressure switch. Rollings explains, "I had some occasional Fourth-gear switch failures when all electric current was routed directly from the dash switch through the pressure level switch to the TCC solenoid. In a stock car running the computer, the pressure level switch sees very depression voltage and electric current, and then we don't want to run the higher electric current needed to direct engage the TCC solenoid through the pressure switch on a long-term basis."

You'll have to drop the trans oil pan and filter to check for the necessary internal parts. If the TCC solenoid, 4th-gear pressure switch, valvebody-side harness, case laissez passer-through adaptor, and internal connectors are already present inside the trans, you'll simply demand the dash switch, almost 10 feet of good automotive-grade stranded hookup wire (non solid household wire), the relay, the relay connector plug, the TCC external Weatherpack connector, and miscellaneous butt splices, band terminals, and spade terminals. If whatsoever of the other parts are missing on your trans, they're available through aftermarket sources.

The Results

Jacoby's Roadster now has amend in-town response with improved mileage and trans longevity on the highway. She'south thoroughly satisfied: "The car feels more lively. It drives a lot better than it did before!"

If you get lucky, you might spot Pam Jacoby and her 1932 Ford Model A roadster cruising the streets of sunny Upland, California.

Lessons Learned

It's like shooting fish in a barrel to have advantage of the 19821990 700-R4's lockup feature in a retrofit, noncomputer application. Wiring the circuit upwards is a simple task for the average hot rodder. A similar scheme works for a TH350C, TH200-4R, and 19911993 4L60 (not-"Eastward").

01] Jacoby's Roadster has a basic four-last ignition switch.

02] Rollings used the switch'due south accessory terminal to supply power for TCC lock-up (arrow).

03] Cars with modernistic fuse boxes can alternatively usually tap into a spare "accessory" cavity (arrow). The primal is drawing power from a source that's "hot" when the engine is running.

04] Any 30-amp single-pole unmarried-throw (SPST), ordinarily open (NO), manual switch works—have your pick!

05] Online-LED-Store sells rocker switch for just $3.99 at Amazon.com. Wiring its tertiary final (pointer) to Ground illuminates the switch's built-in LED calorie-free when the switch is in the "On" position.

06] The switch blends well into the existing dash.

07] An external iv-crenel square 4-terminal Weatherpack connector comprises one element of three-part TCC harness trans TCC example connector system. Pico Wiring sells the Weatherpack with pigtails, eliminating the demand for special Weatherpack crimpers.

08] Next, there's a "pass-through" with Weatherpack terminals on the external side and PacCon terminals at the internal valvebody side (PacCon end shown). Tri Component is i source for the pass-through.

09] Finally, there'due south a mating PacCon connector on the instance's interior side.Mark Rollings

10] A pressure switch closes when the Fourth-gear hydraulic excursion sees pressure. This switch normally screws into the valvebody's 4th-gear hydraulic-circuit passage. Installing a new switch may require dropping the valvebody.

eleven] Alternatively, the servo cover on the trans' passenger side also sees loftier-gear pressure and can be modified to accept the switch. If you're conscientious, its snap-ring retainer and comprehend can exist removed with a prybar and screwdriver.

12] To mount the pressure switch in the servo cover, drill a -inch hole and tap for NPT. It'south possible to force the cover and snap ring dorsum into the case by paw.

13] TCC clutch solenoids are widely available. Usually they consist of the solenoid with ii curt pigtails for splicing into an existing valvebody harness. As far as we know, the only way to become a new PacCon internal main instance connector is via Transmission Parts USA's universal TCC solenoid kit that includes the solenoid, plus the harness, PacCon, and Z-shaped plastic retainer.

fourteen] Universal ISO relays (SPDT NO/NC) are widely available at friendly prices. Rollings uses them to protect the relatively sensitive force per unit area switch from seeing loftier current flow when the TCC solenoid engages. In this app, NC terminal 87a isn't used.

fifteen] Checking for and/or installing the internal connectors, the wires, and the correct within wire clocking and routing requires dropping the trans pan and removing the filter. Now's a good time to replace the Dexron Iii ATF fluid and trans filter.

Contacts

ACDelco; Detroit, MI; 800.ACDelco; ACDelco.com

Amazon.com Inc.; Seattle, WA; 866.216.1072; Amazon.com

Online-LED-Shop (OLS); Ontario, CA; 855.LED.ONLINE or 909.212.0993; Online-LED-Store.com

O'Reilly Auto Parts; Springfield, MO; 888.327.7153 (net orders), 800.755.6759 (store customer service), or 417.829.5727; OReillyAuto.com

O'Reilly Auto Parts Store #2682; Riverside, CA; 951.685.0822; OReillyAuto.com

Pacific Industrial Components Inc. (PICO Wiring); Eugene, OR; 541.688.9646; PICOwiring.com

Summit Racing Equipment; Akron, OH; 800.230.3030 (orders) or 330.630.0240 (tech); SummitRacing.com

Tri Component Products Corp.; Bronx, NY; 800-366-3874 or 718.402.2400; TriComponent.com

Source: https://www.motortrend.com/how-to/hot-rod-rescue-lockup-700-r4-torque-converter-without-computer/

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