4L60 Re-Rebuild for my C20

[LTZ C20]

Some may know, some may not, but I put a 89' 4L60 in my C20 about a year and half maybe 2 years ago to go behind my 350. It's tied into the ECM for my TBI so I have working lock-up. When I got this trans, it was used obviously, but it was a GM SeRTA transmission. Well not knowing it's history, before I ever used it, I had it rebuilt and beefed up. So we put in a corvette servo, hardened steel drum drum I think it's called, couple small things to make it shift firmer along with the servo, racing clutches front to back and upgraded from the stock 4 pinion to the 5 pinion rear planetary gear set from a 4L60E.

Well about 2 weeks ago, one morning on my way to work, I took off from a stop light and the truck never got past second gear, 3rd and 4th never happened, like they were just not even invited to the party. So I drove it with or trans Tech, he confirmed it needed to be pulled and disassembled for inspection.

So diagnosis reported that the 3-4 accumulator piston got a chunk of its seal torn off, if I remember correctly what he said, this sent debris thru the pump. Well that took the anodized coating off the pump slide and dropped the pump pressure. So then fluid to the 3-4 clutches wasn't enough and they burned up progressively from front to rear of the pack. The front going from lightly burned to the back being completely burnt up and a loss of 3rd and 4th gear. He also found the input drum/shaft has some excessive tolerance where bearings go and they could be better. The 3 small aluminum accumulator pistons center holes are slightly worn and not perfectly round anymore. The larger and small spring drums had some springs removed also for firmer shifts. The first builder used lead bb's flattened to plug 3 fluid holes on the valve body separator plate so it would shift harder and put some hole reducer plugs in a few spots on valve body (case side) also for a firmer shift. The 1-2 shift on this thing was always FIRM, (by firm i mean it just about slammed in to 2nd) but I never had any issues with it, it drove great, very responsive, got 16K miles on it with no problems until 2 weeks ago when it literally flipped the light switch off and 3rd and 4th gear went bye bye.

So this new trans tech we have is going to re-rebuild it. It's getting a stock larger servo, new separator plate with no holes plugged, new accumulator pistons, new spring drums with all the springs installed, new input drum/shaft, stock clutches which are thicker than the racing clutches for the 3-4 clutch pack. He said the racing ones can stay in the other 2 clutch packs but the stock ones will be better for the 3-4 pack and of course it's also getting all new bearings, seals, gaskets and such required for a full rebuild. Also a new 5 pinion gear set as the current was damaged, found upon disassembly. I told him to replace anything questionable as I don't want to have to pull this thing out again for a very long time. It will still shift firmer than stock but be much tamer than before, should be a happy medium between stock and slamming.

I will also be doing some upgrades that it never got the first time around. This includes a deep sump aluminum pan from Summit, reusable rubber pan gasket with steel core from Lube Locker. I will be drilling the pan and adding a trans temp sensor from Dakota Digital in preparation for Dakota VHX gauges in the future. I already have an external B&M Super Cooler in front of the A/C condenser.

Another possible upgrade is a better torque converter. The converter I was using was the one it came with when I got it, I'm assuming it's the stock one. Now that it's been thru 2 rebuilds, I just don't feel like taking any chances on it, even tho the 1st tech said it was fine to use the first time and the 2nd tech is saying it's still good to use again. So I'm looking at converters that are best suited for towing needs. I have found some prospects on Summit, TCI Auto and Monster Transmissions. I do need to know a few things tho:

A: What is the factory stall speed for a 1989 4L60.
B: Triple confirmation that 85-up 700R-4's and 4L60's used 30 spline input shafts.
C: What are your guys experienced recommendations on a stall speed and converter for my truck as I have built this to be a strong tow/haul rig. My camshaft did not have any recommendations for increased stall speeds over stock. The truck has a 14 bolt full floater with 4:10 gears which I am very happy with and do not intend to change. I want to be able to make use of as much available torque as possible.

Note: When the transmission was working, I could cruise at 55-60mph, in 4th gear, in lock-up and the engine ran 1500 rpm.

[Irish_Alley]

time for a nv4500

[LTZ C20]

time for a nv4500

Not gonna happen. For this truck, I have zero interest in a manual transmission.

[LTZ C20]

Torn 3-4 accumulator piston seal.


Burnt 3-4 clutch pack.


Damaged 5 pinion gear set.


Good & burnt clutch packs.


Hardened steel drum and large & small spring drums missing springs.


Corvette servo.


Plugged separator plate holes.


Damaged rear gear set.

[LTZ C20]

New deep pan.


Reusable gasket.


Dakota sensor.


Cleaned and ready for assembly.

[1967KaiserM715]

I would have upgraded to a 4l80e, I know quite a few people who have towed with the 60 and they don't last, course you made a few sensible upgrades, so you may be alright.

Good luck, hope it works out well(and keep the pics coming-I like them)


Sent from my iPhone using Tapatalk

[LTZ C20]

I would have upgraded to a 4l80e, I know quite a few people who have towed with the 60 and they don't last, course you made a few sensible upgrades, so you may be alright.

Good luck, hope it works out well(and keep the pics coming-I like them)


Sent from my iPhone using Tapatalk

That's what I wanted to do but couldn't afford it and would have required another stand alone computer. With this I have 1 ECM for engine and trans so it was cheaper. We upgraded everything that normally breaks on the 4L60's. What I really really really want is the 6 speed Allison from a Duramax, even better yet the Duramax and the Allison together but that is a completely different topic.

I'm only concerned with making this one the best it can be. A few guys at the shop have had good words to say about this new transmission tech and his abilities with the older units. So I know it will get fixed properly and he knows my intended use for it and said it will be better this time around. I'll do my best with the pictures.

[Irish_Alley]

all this over one little piece of rubber. good luck with the new one

[LTZ C20]

all this over one little piece of rubber. good luck with the new one

Yep. It's no bueno when stuff decides to fail. I was going to do the deep sump pan and sensor on my next transmission service. But this happened first so I might as well do it now.

[86square]

Good luck!
By the way u said u are from Modesto if u Dnt mind me asking who's building it for u?

[LTZ C20]

Good luck!
By the way u said u are from Modesto if u Dnt mind me asking who's building it for u?

Our new to us transmission tech, his name is Don.

[LTZ C20]

So here are the 4 converters I'm looking at currently.

Hughes Performance
model GM22LXTM
stall 1800rpm
with lock up
30 spline
700R4, 4L60, 4L60E
$409

Hughes Performance
model GM22LTOW
stall 1800rpm
with lock up
30 spline
700R4, 4L60, 4L60E
$384

TCI Transmissions
model 242820
stall ?? doesn't say
with lock up
30 spline
700R4, 4L60, 4L60E
$398

Monster Transmissions
model B29DLLF
stall 1650rpm "low stall"
with lock up
30 spline
700R4, 4L60, 4L60E
$175, currently on sale.

I've read some reviews on Summit's site about the Hughes converters, only 1 out of 7 has been bad, the rest seam pretty good. Summit shows no info on the stall speed of the TCI one, same as TCI's website. The monster one looks pretty nice, I'm not sure whether the "low stall" will be better or not than the higher 1800 stalls.

I still don't know what the factory stall is for the converter I was using.

[Irish_Alley]

monster has a bad rap and a web page just about their "good" tans, stay away. if you want better mpgs you want the low stall if you go with the higher stall then you can get into your power band of the engine faster. low stall is something like 1400-1600 which is stock for sbc bbc and diesel the 1600-1800 is for v6s from what i understand

[Irish_Alley]

http://monster-transmission.pissedconsumer.com/

[LTZ C20]

I've heard mixed reviews about Monster and it seems a bit weird that their version is about 1/3 the price of others that should do the same thing. I've found info that it basically saying stock stall could be anywhere from 12 or 1400 to 2 or 2200rpm depending on application. Doesn't really help me there.