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4L80e hard shift

martin3500

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Split the tranny in my 93 GMC 3500 Crew cab dually 454, 4x4 like a ripe watermelon. Replaced it with a 94 4L80e with a shift kit.
Feels like someone hit me from the rear when it shifts. Despite what everyone told me before I put it in, I read that the 94 has
an upgraded pressure control solenoid that can cause hard shifting in earlier trannys. If the new PCS is an upgrade, I would like
to leave it in there. How can I make it work with my electronics? Should/can I just put a 93 PCS in?

I also have another 4L80e that has a tag indicating the year 2000 on the side of the case, just ahead of the normal location. It is
obviously not that late a transmission as indicated by the shifter, cooling line locations and main connector. It is labeled as a GM
replacement reman. I there any way to tell exactly what this is?
 
You can only run a 91-93 4x4 trans in your 93. You have to change valve bodies and crack the trans open to add the output reluctor into a 94+ to work in a 93.

In 94 GM stopped putting in the 40 tooth output reluctor for the output speed sensor in 4x4's. They changed the transfer case to add in a 4 low signal and used just the speed signal from the transfer case speed sensor, when you shifted to 4 low, the tcase switch triggered the PCM that it was in 4 low, and it corrected the speed signal accordingly.

And 91-93 was the only 4l80e's that had a line pressure accumulator and used the early epc that required a cleaning cycle every 10 seconds. It stroked the plunger in the epc full stroke every 10 seconds, you don't notice it because of the line pressure accumulator dampens/slows the line pressure change. In 94 GM changed to the EPC used in the 4l60e that did not require the cleaning cycle. It also used a spring loaded plunger, so they had to do away with the balance circuit for the epc plunger, and they eliminated the line pressure accumulator. The change wasn't an upgrade so much as it was a cost saving measure by using the same solenoid in multiple units.

91-93 4l80e's should really be viewed as a completely different trans from 94+ 4l80e's. I wouldn't be surprised if you haven't done damage to the 94 trans running it in the non compatible 93 truck.
 
Thanks, THEFERMANATOR, that was a more clear and complete reply than any I got from the "experts" I talked to
before blowing $2500 and a month on this process. I did stop driving it after picking it up from the transmission shop
(which has been in business since the 1960s and have rebuild a number of 700R4 and 4l60es for me)
because I was afraid it would damage it as you say. I am very disappointed in them and have yet to go discuss it with them.
Turns out they appear to have put it in with a TC from a turbo diesel. I can't justify spending any more money on this truck
even though I love it and it does most of what I need if it will fit. I will need to learn as much as I can and do it myself
I guess.

In the meantime I have purchased a 92 GMC 2500 4x4 PU with 454, 5 spd manual and supposedly 3500 axles. They tell
I will need to order brake parts etc. for the 3500, we'll see. It is a sweet pickup. Seems tiny but goes smooth and strong.

I kept the valve body with epc from the original truck which won't help much under the circumstances.
I will need to try to identify the spare tranny I have as well as the TC it came with. This is the only question you
did not address in your reply. Any suggestions?

After driving the 92 manual I might just get rid of all the 4l80e stuff and go looking for an NV4500. It is so nice to make
the decisions and then have the truck do what you tell it.

Thanks to MrMarty51 as well.
I have many trucks, vans, busses etc. I think I may get some good info on many of them from this site and perhaps share
some from time to time. I will find time to list them soon.
 
Can you post pictures of the other trans? Look for any tags on it, labels, stickers, does it have the mounting bolt tab at the 12 o clock position to bolt to the engine, get a picture of the shift shaft and the area around it.

As to your converter, 454's and 6.5 turbo's both got the same low stall single stator converter, so that is correct. If you paid a shop to do the work and they said the 94 trans would work in your 93, then they are liable to repair it correctly. Sonnax makes a replacement 40 tooth reluctor ring that can be installed, but it requires COMPLETE disassembly to get to where it must go. Without it it will read the parking pawls which is only 21 teeth. Unfortunately there is no easy way out of this as the 91-93 PCM cannot operate like the 94-95, so it must have that output speed reluctor in the trans to shift correctly. And you will also need the 93 valve body to get line pressure back down where it should be.
 
The signature line is a good place to list vehicles and any mods thats been done to them.
That the area below the message/reply area, like where Thefermanator has in red about cant have it all and then below that.
It really helps us to identify the wehicle in question, when You are having a problem.
 
Thanks again THEFERMANATOR. The shop took the truck in to replace the 93 case and rebuild the 93 innards.
They said it was not possible to rebuild it but couldn't seem to say why. I cracked the case and drove about a mile
before I realized what the noise had been and saw the trail of fluid. It never ran dry and never slipped. I couldn't figure
out where they benefited by not doing the job, sold no case and no rebuild. Then I came up with a 95 which I was told,
by the seller, would work if the shifter were changed. After the shop installed knowing it was a 95, it had no reverse. The
95 was removed and the seller promised a replacement. When the replacement was not forthcoming I sourced a 94
which turned out to be from a turbo-diesel. The shop installed it without any question as if a properly functioning
transmission of any year would work. They delivered what I have previously described. I found a web site listing specs
for Torque Converters that said the 454 used a medium stall in 93 while the diesel and 350 used the low stall. That is all
I know about that so I hope you are correct about the TC although I'm not sure it means much at this point. The
unidentified transmission is the promised replacement for the 95. I picked up the 93 parts including the reluctor ring. I
haven't gone through them yet but at a glance they look very clean and serviceable with some light brown discoloration
on friction surfaces. At this point however, if I can identify the extra tranny and it is compatible, I may just stick it in, if not
maybe I can go back to the seller and get him to find me a 93 since that is what I asked him for in the first place. I am
enjoying the manual meanwhile in my "new" 92.

I will try to get photos of the mystery tranny on Sunday and post them.

MrMarty51, sounds like a good practice. I don't see a signature line in the reply area so I will just put it here and hopefully serve
the purpose until I figure it out or somebody sets me straight. My truck is one they built while they were trying to figure out how
to build yours.

93 GMC K3500, Crew cab dually, auto, 8' utility boxes, Rynel bumper with 12k Warn winch
 
Not to derail the topic.
At the top of each page is Your screen name, click on that, it will pop down a menu, most all the way down it says signature, start there. LOL
Okay, back on the tracks again. LOL
 
Many catalogs incorrectly list the early 4l80e converters. Up to early 97 6.5's and 454's used the gm-81 converter, 350's used the gm-82 dual stator medium stall converter, and 4.3 vans used a high stall single stator converter(nearly impossible to find except from GM).
 
Where you at? In Phoenix, AZ I get my trans rebuilt for $1,100.00 or so in and out. 4L80E 4x4. Complete cores are $50 or so in case you cracked the case. Prices may have gone up a little, but, this is a lower priced outfit here.

You already paid for a trans so they should finish the work with a proper trans and write it off as warranty and their education.
 
Is the transom water logged from the egg'd out holes? The best solution is to fill those holes with resin and milled glass, then re-drill the holes. Can't do that if the transom wood has water in it. The next best solution would be to apply 5200 sealant around your McGyver solution.
Where you at? In Phoenix, AZ I get my trans rebuilt for $1,100.00 or so in and out. 4L80E 4x4. Complete cores are $50 or so in case you cracked the case. Prices may have gone up a little, but, this is a lower priced outfit here.

You already paid for a trans so they should finish the work with a proper trans and write it off as warranty and their education.
That in and out price, is that removal and installation, or, in and out the door ?
If that includes installation, probably be worth the trip to bring over a vehicle that needs the transmission rebuilt and just have them doooit.
 
Yeah drop truck off with smoking trans and pick it up repaired. Hard parts like gears extra. Or welding up a spun bearing or new electronics... The OD gears are a known wear area on 4L80E's. They do lube improvement mods as I recall. It's been a few years since I had several transmissions done there so prices may have changed.

Family outfit as the son bought the place from his dad.

 
Thanks everybody. THEFERMANATOR, that explains the contradiction on the stall spec for the various engines. I am attaching pics of the spare tranny. I removed the sensor and see that it does have the 40 tooth reluctor ring in there. As I understand what you have told me, this would then have to be a 91-93. That leaves me not knowing what TC is on it but now knowing the diesel and 454 used the same I should be able to use the 94 TC with the 91-93 tranny and get going. I searched guite a bit for this kind of info without much luck. I would think there would be good info on these trannys compiled somewhere. Obviously lots on this site but just luck that I hit it. I am under tge gun right now but will get back soon to list vehicles and info. Even though I don't know much about automatics I have repaired vehicles and equipment from most everywhere but Asia over the last 60 years and might be able to answere a question or two for someone. I am in Northern California by the way so Phoenix is a little too far. Sounds like a good place though.



 

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I find the TC clutch is a weak area on transmissions. It is standard practice to rebuild them along with the transmission: new bearings and new friction. They can also be full of debris from the last trans failure. Used trans with used TC is fine, but, a used TC can trash a rebuilt trans quick.
 
That trans you posted pics of is either out of a van, or is a frankenstein build from somebody. It's a 95/96 case as evidenced by the 2 bosses to mount the nsbu switch and the bosses by the trans plug to mount the shift cable to. You can tell at some point there was a nsbu mounted to it from the broken off bolts in those holes. But somebody has swapped in a short shift shaft which was used on vans to 96 and trucks to 94. I can't make out the numbers in the tag to try and break it down that way. If it does in fact have a reluctor wheel in it, I would be questioning if it was a 2 wheel drive trans that somebody cut the output shaft down on to use it as a 4x4. It is definitely not a 2000 trans, but honestly it looks like a frankenstein to me.
 
Frankentstein, I guess that would fit right in to this process. Sorry the pic was not good enough to read the #s.
The tag says Hydra-matic Cast in case rt. side
Made in USA 8472
13HDP 6 Hydra-matic
Code No. 24203370 9
Hydra-matic
Division of GMC lt. side
Serial No. 8473
00-069 269184
The original tag was removed and this one bonded to the case. I thought I might be getting somewhere when I discovered it had
the reluctor wheel. Did other models continue to use the reluctor wheel after 93? Do these #s make any sense? My understanding is that the first two #s represent the year but maybe they rebuilt it in 2000? It says it was remanufactured as a replacement for GM. I guess just getting one rebuilt is the only way to know what is in them for sure as I think you pointed out a few posts back.
Thanks again FERMANATOR
 
Wow! When posted the order and spacing of the data I tried to send was shifted all over the place.
Tag: Hydra-matic; Made in USA; Code No, 13HDP 6; Serial No. 00-069 269184
Cast in case Rt side: 8472; below that, 24203370 9; Lt. side 8473
 
Only 91-93 4x4's and 2 wheel drive 4l80e's got the reluctor. A possibility is that trans you have was a 2 wheel drive with a slip yoke. Slip yoke 4l80e's can have the output shaft cut down and a 4x4 extension housing bolted on.
 
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