Spotter’s Guide: 4L60E Transmission

What is knocking on a small block Chevy? Could be lean fuel mixture or excessive timing causing pinging or pre-ignition. Could be bad bearings on the crankshaft. Could be worn cam or rockers. Could be broken rocker stud. Could be exhaust manifold leak.. If it goes away within a couple minutes of starting, it’s possibly something called “p…iston slap”.


This switch has a wire going down to the transmission to a detent solenoid inside the transmission that caused the transmission to drop down a gear below 70 mph. We took off the QJet carb almost immediately after we bought the car, replacing it with a Holley carb. You can skip down to wiring part of this article.

Adjustable Vacuum Modulators The vacuum modulator is a vital component of automatic transmissions. It tells the transmission what kind of load is being put on it, allowing the transmission to react with the proper line pressures and shift points.

However I won’t be able to offer custom tunes for modified engines. Please read to the bottom, there is a lot of important info I need to know to properly program your PCM. Bottom of this page has shipping address and a “Buy Now” button for payment. I have gotten a lot of questions if I was still doing programming, answer is YES, I have not stopped doing programming, nor do I plan to at all.

This is my full time job. COM was created in Please let me know if PCM does not match the engine exactly. GM used different injector sizes, fuel rail types etc across engine’s and years. It’s important for best performance to know exactly what the engine is. Also, if you plan to swap intakes from another engine LS1 intake on a 5.

Illustrations Index

Nearly 22 years ago now. Today, it has 95, miles. A large percentage of that 58, mile difference has been off-road in the Pacific Northwest. The rest has been getting to and from the trail-head to leave the pavement. I traced this rig’s history and spoke to it’s original owner not long after buying it. He had purchased it as a dealer “demo” with 4, miles on the odometer.

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Originally Posted by rich weyand The vacuum modulator, together with the governor, controls the shift points on the TH transmission. All stock TH s were manufactured the same; their differences in shift characteristics for specific engines and vehicles were set with the governor and modulator. The governor lives behind a cap secured by a bail on the drivers side of the transmission in front of the tail cone.

It is a little widget that spins with the output shaft. There are flyweights and springs on this spinning widget, and when the flyweights overcome the springs and hydraulic pressure, the flyweights push open a rod valve that lives in the center of the governor shaft. Adjusting the governor weights and springs can be done to adjust the wide-open throttle shift points of the transmission.

The vacuum modulator adjusts the hydraulic pressure to the governor dependent on the engine vacuum. At wide-open throttle low vacuum , the full hydraulic pressure is provided to the governor and the wide-open throttle shift points are selected. When there is engine vacuum on the modulator, the hydraulic pressure to the governor is reduced, and the governor finds it easier to overcome the hydraulic pressure to open the shift valve, so earlier shifts are selected.

Adjustment or replacement of the vacuum modulator can be used to adjust the part-throttle shift points. The kick-down cable on the TH bypasses the modulator and provide full pressure to the governor, enabling the wide-open throttle shift points. The result is that, when the pedal is depressed past the kick-down point, the modulator is bypassed, and the full hydraulic pressure provided to the governor, which will cause the transmission to downshift if it is below the RPM for the wide-open throttle shift point.


The automotive world is increasingly regulated by digital electronics, and hot rodders might as well take advantage of these amenities. This story will look at the evolution of the 4L60E, which is essentially a digitally controlled R4. The original R4 was built in as a Corvette four-speed automatic with overdrive. This gearbox is different because it applies an overdrive to First gear to create Second.

Feb 24,  · Technically speaking, you could just plug all the vacuum lines on it for testing to see if it idles, but you’d have to hookup a vacuum line to the Distributor for .

Would you like to merge this question into it? MERGE already exists as an alternate of this question. Would you like to make it the primary and merge this question into it? MERGE exists and is an alternate of. Merge this question into Split and merge into it SAVE In Carburetors When you get ready to run the vacuum line from the turbo trans modulator to an Edlebrock Performer CFM carb, attach the vacuum line for the transmission vacuum modulator to the bottom constant vacuum source or the plug that is below the throttle plate.

After that, install the vacuum advance to the port that is signaled or right above the throttle plate.

Vacuum ports on a Quadrajet

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Oct 29,  · Most likely you have a TH turbo trans and on the side front is a vacuum actuated can that operates the shift of the tranny. Any vacuum line connected to .

If you stick with 87′ and newer the tranny will have a 30 spline input shaft and a 27 spline output shaft. This allowed me to re-use my drive shaft yoke from the Turbo The bolts going into the R4 are M10x1. Metric torque converter bolts are also required to bolt the converter to the flexplate, GM PN The R4 uses a lockup converter. I love my lockup. The lockup converter allows me to have a high stall and cruise on the highway.

If I didn’t have a lockup converter I would be constantly slipping with my converter on the highway. I don’t use the lockup in any other gear than overdrive and I disengage the lockup under full throttle. It’s great you can have your cake and eat it too, high stall for good launch, lock up the converter on the highway and cruise home.

Automatic Transmission Vacuum Lines

The tech page will grow to be several articles about specific units and the specific mods and the reasons to do those mods. Visit often for updates. This question is hard to accurately answer.

– HARDTOP transmission types: TH, Muncie, Powerglide, T, Super-T, Saginaw, – Intake TCS Solenoid Vacuum Switch Assembly for Big Block Engines This solenoid mounts at the carburetor and has 2 flat electric thermal style prongs and 3 port vacuum outlets. Bracket mounts to the carburetor stud on your intake.

August 10, I think you need to dive in I had a 74 El Camino a while back and needed a trans. I bought a TH on ebay from a company named Jackson Racing. Great service and great shifting trans. There are different flexplates that Chevy engines use, external and internal balance and different diameters. You may have to pull your car apart to determine which you need. Also, the driveshaft length can only be checked once the trans is in along with proper placement of the crossmember.

I believe there are long and short tailshaft TH ‘s. The vacuum hook up for the modulator is easy, right to the intake manifold.


Ported vs manifold vacuum advance March 21st, , This was written by a former GM engineer as a response to a similar question on a Corvette board: As many of you are aware, timing and vacuum advance is one of my favorite subjects, as I was involved in the development of some of those systems in my GM days and I understand it. Many people don’t, as there has been very little written about it anywhere that makes sense, and as a result, a lot of folks are under the misunderstanding that vacuum advance somehow compromises performance.

Feb 21,  · Hey guys. I was wondering if any of you have dealt with this trans before, its a Jegs Performance TH without a kickdown hookup. It says in the description that if you remove the block off plug that is installed in place,warranty will be void.

Although carburetors haven’t been used on new cars since the mid-’80s hot rodders haven’t moved as quickly. There’s no denying that a well-tuned fuel injection will perform better than a carb, but there’s still a stigma left by some of the early aftermarket kits that left a whole lot to be desired. One of the best ways to retrofit fuel injection is to still take advantage of the research General Motors put into it and find a used factory system.

We’ll be following this article with an actual installation, hopefully, next month. Why should I swap to fuel injection? Swapping to fuel injection has many advantages. Your engine will last longer and have better low- and mid-range torque. Can I get a Tuned Port Injection unit out of salvage? Yes, the only part to wear out is the shaft in the throttle body which can be replaced with a larger aftermarket throttle body or a new factory unit.

Install: B&M Vacuum Modulator for GM TH350 & TH400 Automatic Transmissions – Part # 20234

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