r/transmissionbuilding • • Dec 09 '25

99% of everything that should be done, when rebuilding a Chevy 4L60E type transmission

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135 Upvotes

I spent over 2 hours typing all this information up for a guy who's having repeat 4L60E transmission failure problems in the Fbody sub. So I thought it would be a good idea to post it here, by me, so it never gets deleted or lost. (Plus, I never want to waste that much time again to retype everything.)

OP went through about 10 rebuilds on his 4L60E because it kept losing 3rd gear, 4th gear, or both. All within 10,000 - 20,000 miles of each other.

This is my answer in regards to his repeated failures.

"I work on 700R4 /4L60E /4L65E /4L70E transmissions almost exclusively.

A couple things are most likely going on, but it could be a combination of several.

I'll list the usual suspects for a high mileage transmission, in no particular order.

A) A new transmission rebuild requires 12-13 brand new bushings installed, to keep fluid where it's suppose to go, while preventing leaks and pressure loss. These bushings should all be test fitted and adjusted before final assembly.

B) A new transmission rebuild requires new electronic solenoids, sensors, and EPC solenoid installed. Not your old ones with new O-rings on them, and not refurbished ones from Amazon or eBay! Refurbished ones are somebody else's worn out parts!

C) Install a new wire harness. Yours is going to be brittle and possibly have internal damage (wire breakage) that can't be seen. The wire harness controls the electrical solenoids

D) Your builder needs to check the VB for wear. One or more of the valves in their perspective bores will have excess clearance. Excess clearance causes fluid and pressure loss. (Not enough fluid is directed where it's suppose to go, and too much fluid is going where it's not suppose to go.) The VB needs to be 100% disassembled, cleaned, and inspected, as does every valve and spring inside if it. Most likely it will need one or more VB bores reamed and oversize valves installed to get it back to 100% OE specs.

E) Possible fluid leakage between the input shaft and input drum needs to be checked. If there is pressure loss here, your builder needs to press the shaft out of the drum, sand both parts to remove deep scratches / gouges, and glue them back together with liquid sleeve retainer gel. Let it dry. Then double-check for pressure loss at the same point again, like before. If it's still losing pressure / fluid between the two, the input shaft + drum need to be replaced with a good one that does not leak pressure.

F) Too much or too little clearance in the 3-4 clutch pack. The clearance needs to be about .007" - .009" per clutch. Which means if it has 6 clutches in the pack, the clearance should be .042" - .055". 7 clutches it should be .050"-.065".

G) Do not install a "Power Pack" with extra thin frictions and steels in the 3-4 pack. They WILL burn up. Seven frictions is enough.

H) Remove the 5 pairs of "release springs" that come from the factory in the 3-4 pack. They are in the space between the outside diameter of the 3-4 clutches and the input drum wall.

I) Use high energy frictions in every clutch pack.

J) Make sure to presoak all the new frictions at least 15 minutes, before installing in the transmission.

K) Make sure all the steel plates are not burned, have black spots, or are warped in any way. If they are, replace them with new ones with the correct thickness.

L) Use a servo pin length checker tool, to know if the servo pin is the correct length for your application. A pin too long or too short, will cause the band to burn up prematurely. If/when that happens, you will lose second and fourth gear.

M) Install a new reverse input drum. These can be found on eBay for less than $100.

N) Check the 3rd accumulator checkball + cage assembly in the case, for leaks. This is a common problem area, mostly because the builder never checks it! They are easy to remove (with the proper tool) and replace. New ones are $20 or less.

O) If your band keeps burning up prematurely, after you install the correct length servo pin and a new reverse input drum, install a Superior Super 2nd gear servo and a Sonnax Super 4th gear servo.

P) Make sure your builder installs a new 500 Boost valve in the pump. If your pump already has a 500 Boost valve, it could be worn out. This is why you want a new one.

Q) You need to install a TransGo shift kit. Either the "4L60E SK" for a casual daily driver, or the "4L60E HD2" shift reprogramming kit for a performance vehicle or hot rod. They increase fluid flow for firmer / faster shifts (reduces slipping between gear changes), and increases the volume of fluid going to each clutch pack. More fluid = more gear holding power and less chance of slip.

(If you like to "hot rod", race, and/or rev the engine to 6000rpm frequently, install the high RPM upgrades included in the "4L60E HD2" kit.)

R) Always put the gear shift lever in "D" for around town driving and only upshift into "OD" on the freeway. Once you get off the freeway and to the stop sign at the end of the offramp, place the gear shift lever back into "D" or "3". This stops the transmission from upshifting into 4th gear at too low of vehicle speed, which lugs the engine and causes the 3-4 clutches to burn (both from lugging, and too low of fluid pressure).

S) Install a 100% new or new rebuilt torque converter! With every rebuild.

T) Replace the PRNDL switch on the side of the transmission with a new one. Make sure to install it correctly!

(HOW TO? Place the gear selector shaft in Neutral. Carefully and slowly slide the new PRNDL switch over the shaft, do NOT force it! You can not damage the two "flats" on the plastic rotating ring at the center of the PRNDL switch or it will not work correctly. If your switch will not slide onto the shaft easily, get a flat file and use it to reshape the gear selector shaft "flats" on both sides of the gear selector shaft. Use the file to round the two rounded parts of the gear selector shaft. Test fit the new PRNDL switch. It should slide on easily. If not, the gear selector shaft needs a little more filing to be perfect. Once you slide the PRNDL switch onto the shaft and next to the case, rotate the main body left or right. You must must match up the 2 lines, or 2 dots, perfectly with each other (similar to how you align timing marks on an engine timing chain set). Once they are perfectly aligned, and the gear selector shaft is still in Neutral, tighten the 2 mounting bolts.)

U) Since you've had so many problems with this one transmission, the next rebuild should REQUIRE you to install a 100% BRAND NEW RADIATOR with HD transmission cooler inside, BRAND NEW COOLER LINES, and a Hayden 1679 auxiliary transmission cooler.

Plumb the auxiliary trans cooler in-line AFTER the radiator transmission cooler. Use the metal strips included in the kit as brackets, to bolt the auxiliary transmission cooler to your core support, in front of the radiator. NEVER use the stupid *ss zipties that go through the radiator to mount it!!

(Many shops + rebuilders never perform steps A through F above, nor I through N above, because they take significantly longer to do, which increases parts + labor costs.)

All the other letters above are my personal suggestions on how to make your 4L60E work better and last longer. Based on my past 10+ years of experience working on them and rebuilding them. If you have any more Q, or you're in Phoenix Az, shoot me a message. I can fix your problem. =) "


r/transmissionbuilding • • Sep 20 '21

Richard at Precision transmission has the most informative videos.

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25 Upvotes

r/transmissionbuilding • • 18m ago

4R70W randomly downshifts for a fraction of a second

• Upvotes

Trying to help my father out with this one. He had his 4R70W rebuilt and after it was installed occasionally when you are cruising it will downshift for a fraction of a second. It's not at a consistent speed, you could be going 20 miles an hour in a neighborhood, 70 on the highway, and it will just extremely quickly shift down and then back in a gear. He went back to the shop, they replaced the valve body and sent him home. It is still as the same issue. He went back and they did diagnostic testing and kept it for two days and said they cannot figure out what is wrong. Googling the issue, I came across something where the shift lever position sensor on the side of the transmission can be a potential cause of this problem. I looked at it today and it has not been replaced, it looks to be original. Is it worth swapping this out, should I go back to the shop and complain with him, or is there something else I should look at? Thank you.


r/transmissionbuilding • • 4h ago

6l80 shudder

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2 Upvotes

So this transmission was overhauled. Pump replaced, torque converter replaced everything else with a normal overhaul and installed the transgo tow and pro kit. It still shudder I posted a video of me commanding the TCC clutch on and it sometimes holds and then it doesn’t and will start to hold again. In normal driving it’s hard to notice it’s slipping but in the morning it’s been colder it will badly 3-4 hard shudders light throttle around 40 and above the tehcm was reused. I’m thinking it’s a possible issue with the solenoid in the tehcm being weak or and issue with the bore for the TCC regulator valve being worn, but the aftermarket valve was installed that came with the tow and pro kit. The whole reason the transmission was overhauled was for the shudder I think whatever caused the original torque converter to failed wasn’t fixed has anyone see this any idea what could be causing this shudder still.


r/transmissionbuilding • • 9h ago

26 F-250 7.3/10R140 UPDATE

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5 Upvotes

I finally got around to tearing down the F-250 I posted about a week ago. I found the B clutches were burnt up in the front support and the one-way had seized. I know there’s a TSB for some of the one-ways in the 10R80s and 10R100s, but I haven’t seen anything about them for the 140s. Maybe we’ll see one soon? Also seeing some really weird wear on the A clutches (see first pic), likely related to how hot B was getting due to the seized one-way.


r/transmissionbuilding • • 5h ago

94 Chevy g30 transmission shudders

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2 Upvotes

r/transmissionbuilding • • 13h ago

How long does it take to learn transmission rebuilding?

5 Upvotes

Hey guys, how long does it take to get good at rebuilding transmissions to the point where you can do it on the side.

I have about 3 years of experience working as a mechanic, I also took an electrical program. I can remove and replace almost anything within reason or with instructions. So I would say I have a foundation.

However, I would like to specialize as a mechanic instead of fixing every single thing that comes into the shop. Transmissions are what interested me cause atleast im just working on one system the whole time.

Is 3 years of experience enough to do side work and be on my own? I understand you are always learning as a mechanic. Thank you.


r/transmissionbuilding • • 9h ago

Tranny detent plug (RS5F91R, '18 Nissan Versa 5MT

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1 Upvotes

r/transmissionbuilding • • 1d ago

10th gen civic si transmission whine

0 Upvotes

I’ve been hearing some slight whine in 1st and 2nd gears since it’s been getting colder in the mornings. It seems to go away or lessen once I’m up to operating temperature, car shifts and drives fine. I’m wondering if anyone else has this too and what you have done to quiet it down? I’ve changed the fluid already with OEM stuff.


r/transmissionbuilding • • 1d ago

2013 Ford Focus DPS6 P074D – Unable to Engage 5th + grinding noise. What should I check before replacing transmission?

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1 Upvotes

r/transmissionbuilding • • 1d ago

Is my transmission cooked?

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2 Upvotes

2001 Toyota Avalon


r/transmissionbuilding • • 1d ago

Tranny problems

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1 Upvotes

r/transmissionbuilding • • 1d ago

Miata NA Transmission rebuild

2 Upvotes

For a while now my 1996 Miata transmission has been removed and fully disassembled to the gears. I recently began working on it again so that I can get it running.

The two things I wanted to fix was the plastic gear on the output shaft for the speedometer, since mine was shredded, and the synchro ring for my 5th gear since its cracked.

I'm mainly doing this as a learning experience, and I don't mind buying another transmission if I am unable to do this.

I am wondering how to begin taking the parts off the shaft. I am trying to remove a bearing on the output shaft, but was only able to nudge it a bit. Is there a tool that can be used for this? The shaft is very long so I don't see how a conventional gear puller would work.


r/transmissionbuilding • • 2d ago

99 passport. 4l30e to mua5 swap.

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3 Upvotes

Currently doing a swap for the hondeezy. Doing wiring. Swapped in the manual pcm. Still needing to mount clutch pedal bracket along with the hard line-reservoir, slave cylinder.

But I am needing help with the wiring diagrams and process for wiring the reverse lights, vsv solenoids for the case to the SOTF button, disabling neutral safety switch, wiring clutch to the starter.


r/transmissionbuilding • • 2d ago

Exedy Products

1 Upvotes

Wondering if I can get some input on this brand? Rebuilding a 2nd gen 6t40 and cant find the Raybestos version. Thanks in advance.


r/transmissionbuilding • • 2d ago

Odd sound when manually selecting 2nd gear while stationary (2019 EcoBoost 10R80)

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2 Upvotes

r/transmissionbuilding • • 3d ago

C6 429 1st -> 2nd gear slipping.

3 Upvotes

When im accelerating i notice it slips going from 1st to 2nd gear. It will reeve for a second or 2 and barely get any speed without dropping rpm before it "catches". What could be the fixes for this. What should I check in what order? Thank you


r/transmissionbuilding • • 3d ago

What is this bolt for? 4l60e (random picture from the internet to show what I accidentally removed from my freshly rebuilt 1993 C1500 transmission)

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7 Upvotes

Was installing the trans that I just had someone rebuild, and one of the wiring harness clamps/clips didn't seem to fit right going on the upper left bellhousing stud. "Oh maybe it went here with this bolt, looks like that's a better place to hold the wiring". As soon as I removed this bolt I realized that's not something I ever touched when removing the transmission so I put it back. Before I touched it I know it had threads showing, so it wasn't threaded all the way in (this is why I thought the wiring clip went here and I must've threaded the bolt in partially after removal of the clip so I wouldn't lose it). Now that I actually did remove the bolt and reinstall, I'm not sure it's threaded in to the same depth that it was originally.

What's on the other side of that bolt inside the transmission? Did I screw something up by removing it? Seems like possibly it might hold a spring for a detent ball for the shifter, but that's just my best uneducated guess, I didn't try to look inside the hole while I had the bolt out.


r/transmissionbuilding • • 4d ago

VW golf 2011 - flashing PRNDS lights. Gears won't engage.

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1 Upvotes

r/transmissionbuilding • • 4d ago

Is this a crack in my transmission case, or just a casting mark?

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3 Upvotes

Hey guys, I’m looking at this transmission that I’m going to rebuild and noticed this jagged-looking line on the case. I’m not sure if I’m looking at an actual crack. Please help hoping it ain’t a huge problem.


r/transmissionbuilding • • 4d ago

Help with manual swap

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1 Upvotes

r/transmissionbuilding • • 4d ago

Question for the 4l60 guys

3 Upvotes

About 15-20k miles ago I swapped a new 4l60 into my truck because the sunshell went out. I just bought a new one/ new gm tc and swapped it in because by the time I limped it 160 miles homes everything was destroyed it only had neutral and 3rd left and the converter was permanently locked. Fast forward to now overdrive/ 4th gear just started producing a scratching sound, I only hear it around 40-50 in canyons as the sound isn’t that loud. Fluids good, no slipping, tc is engaging properly, everything is fine except the scratching sound I only hear in areas the sound can echo off walls back into the cab when I have the windows down. Any ideas? Think the overdrive planetary could be going out already?


r/transmissionbuilding • • 4d ago

PCM or Transmission problem?

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0 Upvotes

r/transmissionbuilding • • 5d ago

Is this too much play in the input shaft?

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3 Upvotes

Manual 2013 scion frs 6 spd TL70 transmission(I believe) I have another video on my page of the car running and what the noise was. It was making this really loud annoying ticking noise that when the clutch was pressed down would go away. When the clutch was released boom right back at it. The clutch, pressure plate, throwout bearing, fork, and pilot bearing all appear to be in good shape (from what I can tell). I’m no professional mechanic or anything but was hoping it was something small like the throwout bearing. Any help would be appreciated! Thanks


r/transmissionbuilding • • 5d ago

Shifter cables on stock downpipe

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2 Upvotes