Helping a friend with a '92 GMC 3/4 ton with 199,000 miles he will be using for landscaping. Eventually will be towing a small to medium utility trailer as his company expands. PO used truck to haul a 5th wheel trailer. Had added a aux cooler which bypassed the internal rad cooler (looks like it was never used still had plastic shipping plugs in). Grille was rubbing on the fins and it had started to leak. Replaced with a B&M 70266 and got factory replacement lines to utilize the in rad cooler so it should be all good now.

Trans looks to have been rebuilt before, has the updated case connector and replacement harness. Shifts stock/soft. I will be dropping the pan this week to see general condition, if the EPC has been updated,etc. I currently am on the fence on what mods todo. Unless the trans is totally garbage we do not want to overhaul at this time. Here were my ideas:

1. Getting Sonnax SureCure kit and doing valve body mods only and new pressure regulator (stock not the LB1). Increase shift hole sizes for increased shift feel and to increased trans life, block 4th accumulator etc.
2. Transgo HD2 kit for dual feed without removing trans. I have used this kit before. Don't do the pressure relief mod.

3. Pull trans,internal dual feed, pump mods, modify stock or transgo separator plate, increase shift holes,block 4th accumulator,etc.

Any help appreciated,thanks.


EDIT: I have built a vac tester to test the valve body and can get local trans shop to do the AFL valve fix for me if it tests low.

 

No TransGo "Sandwich" Separator-Plates (when "dual-feeding" the Direct-Clutch the proper way).

 

Removed valve body tonight. Very little debris in pan was pleased. Has had a Transgo SK-4L80E installed. Has the pressure relief valve, which I will get rid of. Stock separator plate is beatup, will be getting new 94+ separator plate and torlon check *****.

Few questions:
-Transgo has you change the accumulator valve springs. I have a stock one from a '07 express, should I swap it or keep the transgo?
- With the Sonnax LB1 boost valve, I read to use stock springs as the extra pressure isn't needed until high HP. again, I have stock springs from a Express
- Being a '92, this has the PCS valve in accumulator housing. I will be using a '94+ separator plate, can i leave this valve&spring out of the housing. should I just source the newer style housing and be done with it? EDIT: the PCS has been updated to the newer style.
- blocking 4th accumulator, is this something that should be done on ALL builds? As mentioned HD work truck with towing in the future. I assume if blocked i should go conservative on shift hole size?

 

Do not use the TransGo Pressure-Relief Valve.

When installing a new Valve-Body Separator-Plate with new Torlon Check-*****...
You must make a new Seat in the Separator-Plate with an old Steel Check-Ball for every Check-Ball location.
Otherwise the new Torlon Check-***** will not seal well.

Yes, use the Stock Pressure-Regulator Valve-Spring with the Sonnax Boost-Valve and Sleeve.
No additional Line-pressure is needed.

I am not very familiar with the TransGo SK-4L80E parts Set...
Unlike the 4L60E, the TransGo Sets are not commonly used by Transmission Builders that specialize in High-Performance Automatic Transmissions.

Obviously I know that you are looking to build a Higher-Performance Unit for a "Work-Van".
I believe that you are referring to "accumulator valve springs" as the two different Springs that TransGo provides for the Accumulator Valve-Train...
and NOT for the Accumulator Piston-Springs.

The Accumulator Valve-Train for the 4L80E is configured so that a firmer Spring makes the Shifts softer...
and a softer Spring (or NO Spring) makes the Shifts firmer.
I personally would use the Stock Accumulator Valve-Spring.

For a "Work-Van" or Truck that does towing...
I would keep the 4th-Accumulator active, unless you are going to have the Tune edited.
Without the 4th-Accumulator, using the Stock Tune...
A damagingly harsh Shift can occur from 3rd-Gear to 4th-Gear while the Torque-Converter is locked.
This can be prevented by editing the Tune; and then you can omit the 4th-Accumulator.

 

I do a lot of box van and tow truck 80e's.

my recipe is a CK purple spring, dual feed, rollerize the output to case and reaction to output, feed more oil to the planets via the sun gear lube mod. I drill the shift orifices to .075/.092/.085 respectively. perhaps most important if the owner is not the operator...or if he is forgetful...sonnax overrun clutch apply kit. Fresh planet thrust washers are a must-have!

If its a carry-out I usually leave the 3-4 accumulators. If I am doing the drivetrain complete, I delete the 3-4 housing and tune the computer to not allow shifts while the TCC is locked past about 15% throttle.

 

Thank you vortec & Doug for the information.

vortec, yes I was planning on upgrading to the 94/95 PCM. I have the hardware to tune and burn chips to change stuff in the tune. I am not sure if it stays locked up when doing a 4-3 downshift,I only drove the truck for a few hours before parking it at my shop.

doug, I will reference your recipe if/when we ever overhaul his transmission. for now we have already dumped a few grand getting the truck caught up on maintenance and I currently don't have the time to pull the trans and do any upgrades. Your shift hole sizes was exactly what i was thinking. I did HD2 kit for a friends Express van about 5 years ago and bought from Dana, 1-2 was 0.090" IIRC and was too firm for my tastes even though the owner loved it. 2-3 (0.086") was pretty tame and 3-4 was ok (0.090").I should probably double check the calibration make sure i can disable lockup on a downshift,but fairly sure i can.

 

Doug, if you are leaving the accumulators do you use stock springs?I kept the original 3rd accumulator spring from the Express which appears to be the 24200436 judging from the remaining paint on it. The current 3rd accumulator has a long spring. Looks like Sonnax makes a more durable version of the most current GM spring 24200436. The 4th spring is blue, looks similar to the current Gm 8675634 spring.

​Also, do any of you use the Sonnax shift valve springs? Any benefit to them?

It looks like I can leave out the TS compensator spring and piston when going with a 94+ separator plate, but I will be retaining the early accumulator housing, I will have to check that no separator plate holes are feeding it before I do this.
EDIT: Looks like i have to block a passage in the accumulator housing if I use the early accumulator housing.

 

yep stock springs in the ones i leave the 3-4 accumulators in.

i do not use the sonnax shift springs. I just make sure the AFL valve bore is 20"hg vacuum or I ream it for the transgo valve.

 

Regarding the line to lube mod. While I do not have the Transgo SK-4L80E (not HD2) instructions, I believe they advise to drill the hole in the pump for line to lube. is there anyway to confirm this without pulling the pump? Can it be checked with a gauge once on the road? I purchased the Sonnax PR valve but didn't realize until after that this mod may have been done internally when the shift kit was installed before (pretty confident at last rebuild).

 

are you doing a line pressure bump? I would not sweat using both a .060 line to lube hole and the sonnax PR valve...the sonnax hole is like .040

 

I will be running stock springs with the Sonnax LB1 boost valve. from what i've read it is not necessary to run more pressure until much higher power levels. Transgo only calls for a .042" to .055" for the pump lube to line mod. as long as I won't do any harm running the sonnax valve, I will install it for now. Can put stock back in when it gets rebuilt and I can verify if the pump has been modded. Thanks.

 

I agree with Doug.

The 0.040" Passage is considered small at stock Line-Pressures.

 

Great, thanks doug & vortec again!

I got my DIY vac tester together this afternoon, once I figured out how to calibrate it I used the Sonnax guide.... https://www.sonnax.com/tech_resource...uum-test-guide

3rd/Reverse checkball sleeve
inboard: 25"
outboard: 22"

3-4 shift valve: 19

2-3 shift valve
inboard: 18.5
outboard: 12

AFL filter: 0

low/reverse checkball
inboard: 25
outboard: 9.5

1-2 shift valve
inboard: 18
outboard: 16

TCC regulator valve
inboard: 24
outboard: 21

AFL valve: 23.5

Accumulator Control Valveinboard: 12.5
outboard: 15

The AFL filter has been modded per transgo, where you remove the o-ring and install the tapered plug in the bore. Last builder really hacked up the filter so I will replace along with Sonnax kit. Every thing else is repairable but I am worried about the 2-3 shift valve and to some extent the 1-2 shift valve even though it passes (I think).


EDIT: for my vac tester only had a 0.034" drill bit for my calibration "plug" not sure if this is a big deal or not...

 

Regarding the 0.034" Air-Bleed for the Vacuum-Pump... what is the highest reading attainable?

Could you Post Images of how you are performing the Vacuum-test, for the locations that were only capable of pulling a low Vacuum-Reading?

Generally the AFL and TCC Valve-Train show the worst results...
However, the other Valves can show sealing issues as well (which may be the reason for the lower Vacuum-Reading that you found).

 

How much weight will the truck be pulling and what rear gear is in the truck ? Look on the door and look for GT5. If the code appears the truck has 4.10 gears. More rear gear helps take a load off the transmission when towing.

I dont know much about the 4L80E transmissions
myself but however I do own one (1997 C2500 454 vortec) . I bought my truck as a spare vehicle and a emeregency tow rig. I plan on towing my car when needed on a open 20 foot trailer. I plan on making 3 simple mods to ensure the life of trans and hopefully helps it. Heat is a transmission killer. To combat against that I plan on doing the best deep trans pan on the market (researching now) and a 40K tru cool trans cooler. To monitor the trans temp I recommend getting a trans temp gauge. Glowshift seems to have one that won't break the bank but has a good reputation and customer feedback. Hope this helps.

 

my answers in red

 

I would run with all those numbers except the AFL valve. that'll cause issues. I use the transgo kit. the reamer stays sharp for about 4-5 "refills" 200-300 rpm, jokisch brand tapping/reaming paste.

 

Doug, replace the AFL valve even though it vac'd excellent? You're not worried about the accumulator control valve even though it tested below spec? FYI, I will not be blocking the 3rd and 4th accumulators.

 

my mistake! I glanced too quickly and mistook the ACV for the AFL numbers. I'll compare the numbers to my "archive" and get back to you.

 

ok my records show the inboard ACV ranges from low 12" to high 15" and never much higher.

the outboard averages 16.5"

when it's low I use Grady's trick of using a tubing cutter to raise a radial burr on the plug in the AFL bore. I do one burr inboard and one outboard on the edges of the plug. I am usually able to get the vac to 16" which should stroke that valve to the open position.