Diagnosing GM Transmissions

The transmission swap in my ’81 is finally completed. Well I had some bigger hurdles to overcome but the car is running again. The main obstacle was that the R4 does not just bolt in and the only way to make it work was to modify the transmission crossmember. Now the bracket did fit but the area of the speedo gear box did touch the crossmember. It was quite hard to figure out all the dimensions specially with a car on jackstands and me crawling under it. A good welding shop can do the entire job in about 1 hour I guess. Once the trans was in , I measured the lenght of the driveshaft and had it shortened accordingly. While they were at it, I also had both U-joints replaced. The startup went without problems. Steve from Bowtie Overdrives was very helpfull.

JEGS Performance Products 60300

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 transmission was first introduced by General Motors in and used up through It is sometimes also referred to as the 4L The R4 was one of General Motors first over drive automatic transmission and was used in everything from Corvettes to pickup trucks.

If your speedometer reads wrong, don’t suffer. A very easy operation. Simply lift the front of the car and find the cable going to the side of the tranny. The cable is removed easily and the gear slides into a metal housing that also is easily pried out of the tranny with a screwdriver. You need to calculate how far off your speedo is before you pull the gear.

This particular gear has 22 teeth, so buying the 20 tooth gear makes the speedo more accurate, although I think it is still around 2 mph short at 70 MPH. Anyway, the point is, if you have an inaccurate speedo, its a very easy fix and inexpensive too. However, ensure the reason that your speedo is off because a different plastic gear is used for your specific combination of differential gears, tire diameter and transmision.

Check the manufacturer info on things like recommended tire size, rear end ratio, drive gear in the transmission pain in the butt if this is wrong , and driven gear specs. If you require a reduction gear, that info is on there too. Especially if you have numerically high gear ratios like 3. All these things matched together equal fairly accurate speedo readings.

The C-clamp method of compressing the clutch packs took a couple of extra hands be sure to compress the C-clamps evenly and there were a ton of small parts to keep track of.

Swapping out a TH350 for a TH700R4

I am attributing that to my errors with the tape measure in my haste to get mine measured so I could get back into a warm house, and I am simply using the published specs. First up, let’s tackle overall length and case length. Overall length is important for the final driveshaft length and the case length is important for the fitment to the transmission tunnel.

The R4 is a good transmission for a retrofit into an older car. It has a to 1 overdrive ratio making even gears great on the street.

It is sometimes also referred to as the 4L The R4 was one of General Motors first over drive automatic transmission and was used in everything from Corvettes to pickup trucks. The first R4 had their share of issues. Here is a list of things to look for when considering buying a car with this transmission. This design was subject to failure because it really need more spline to handle the load properly.

In they introduced a 30 spline input shaft which was much stronger.

700R4 Transmission Parts

We offer several versions of this trans for applications up to horsepower. This trans has a low first gear ratio of 3. This trans was built with a Chevy only bolt pattern, but we have a package for Buick, Olds, Pontiac, and Cadillac people so you can enjoy the benefits of this excellent transmission too. We also provide a custom rebuild service for those interested in keeping the original trans but need an upgraded version to handle additional power mods.

Call for more details. The built-in display and keypad lets the user adjust and tune for their specific application and diagnose problems should they occur.

It is very important to set up the Throttle Valve (T.V.) cable linkage properly to prevent damage to your transmission. I can’t stress how important the geometric relationship of the hook up point on the carb for the T.V. cable is with this transmission (see following pages).

You need the low-vac switch so the converter will unlock in low vacuum situations, such as going up hill and heavy throttle. The brake cancel switch unlocks the TCC when the brakes are applied. Trucks that came stock with R4 trannys came with a low-vacuum switch and a brake cancel switch. The stock low-vac switch didn’t let the TCC unlock soon enough with this mod.

I checked the vacuum on the stock switch and it kicked in at 3. The vacuum switch I recommend works real well as it kicks in at 7. The brake cancel switch on R4 equipped trucks also disconnects the cruise control if equipped when the brakes are applied. Are you are doing this mod for one of the reasons I did, to get rid of some of the wiring and vacuum hoses that came on our trucks. This is one of the reasons I did this.

The factory installed a couple of different types of pressure switches depending on the application.

What You Need To Know Before You Buy A GM With A 700R4 Transmission

By Jefferson Bryant January 23, Hot rods are all about personality. The transmission rarely gets much more than a single thought: For the purpose of this story, we are going to throw out the whole stick-shift thing; this story is all about high-performance overdrive automatics. Modern automatic transmissions go far beyond the old slushbox technology inside the typical TH or C4 you find in most hot rods.

Mar 04,  · and I would always be on the look out for a new van, or have a back up truck ready to go. Now I will have a back up automatic transmission built and ready to install.

Built for the 6. It overheats and can’t survive in a diesel truck. My trusty ’84 C was still running its original R4 after , miles, and now was subject to the increased torque from my customized naturally aspirated 6. This hot new engine, pushing around non-turbo horsepower out the flexplate, only emphasized the flare slippage I was experiencing on the shift.

My planned Nitrous Oxide upgrade in the future would only make the situation worse, like scattering tranny parts all over the secret “2Fast, 2Furious” dragstrip I had stumbled across just outside of Miami. So I began researching what R4 upgrades were needed and what companies offered them before selecting a replacement transmission.

There is a wealth of R4 information available on the Internet, and the links at the end of this article are the most useful ones I found. One caveat, however; the person publishing the information on any given website is probably NOT the technician who will actually be building your transmission. Further research is necessary on the reputation of any given supplier. The Diesel Page Forums are a good place to start. If you cannot locate the information you need by forum keyword search, just post your question and watch the opinions come pouring in.

This month in Part One, I will discuss the operation of the R4 and highlight some of the upgrades that are currently available to improve both performance and durability. In the Beginning, about Historically, the new-for R4 grew out of the venerable Turbohydramatic , with the addition of a fourth overdrive gear and a lock-up Torque Converter Clutch TCC.

GM 700-R4 Overdrive Automatic Transmission – Working Under Pressure

Frist Budget Bracket Truck: Welcome to the forum, Waid! Also, while my S10 project is not a budget build, my Tahoe swap was. In fact, I will be yanking my expensive sbc bracket motor in the future for a junk yard 5. I would save that until last though, so you know what to have it tuned for. PCM for less can also supply a computer, but there is a core charge.

THR4 Lockup Converter a GM service manual for the year/model transmission you are working with to properly identify the components and wiring hook-up for your unit. Due to the large number of variations from year-to-year and model-to-model of the stock wiring hook-ups, it is STRONGLY RECOMMENDED that you obtain a GM manual and.

Your hub for horsepower Get first access to hit shows like Roadkill and Dirt Every Day Join free for 14 days now All automatic transmissions use hydraulic pressure to apply friction components; either bands or clutches shift into each gear. The R4 as well as the R and the 4L60 uses a cable called the throttle valve, or TV cable connected to the throttle linkage to establish that pressure.

In many cases, the shifts are poorly timed and may be early and soft, late and harsh, or a combination of both. Downshifts often fall into their own category of weird, and no amount of fooling with the TV cable adjustment seems to make things right. And although there are other scenarios that cause damage to a R4, what happens in many cases is basically this: The engine begins producing increased torque before the transmission is ready for it.

Here are his comments on a new and improved R4. Line pressure stays between and depending on oil temp and throttle position. At warm idle, rpm in gear, it drops to lbs. Line pressure fluctuates due to engine speed and transmission pump rotor speed, which controls oil volume and pressure. The line pressure increases as soon as you crack the throttle and the pump rotor speeds up. This allows me to back it off a little and tone down the shift.

How to Install and Adjust 700R4 TV Cable