ez2cdave

I have a question for the 4L80E experts out there . . .

Can the 4L80E be programmed ( and survive ) to allow high-RPM, high-HP operation in 4th Gear ( Top End MPH ) ? ( No manual valve body )

I want to know if the transmission can function as a true "4-Speed" and not just as a "3-Speed, with OD, for economy" ?

If so, how much Torque / HP can 4th Gear handle ? What, if any, are the upgrade options to increase this ?

Thanks !

ez2cdave

Not a single response . . . Really ?

ez2cdave

MORE than THREE YEARS and NOT A SINGLE RESPONSE . . . Really ?

Aaron R.

Yep, really.
Be offended. Some of us find it humorous.
Maybe nobody likes you.

ez2cdave

Maybe . . . But, I am not offended . . . Diasppointed, but not offended.

I don't post on Forums to be "loved" . . .

QwkTrip

iTrader: (22)

This thread has been diagnosed with a chronic case of spoon feeding.

vorteciroc

Unfortunately Not...
4th-Gear was never designed to really support Power.
The Overdrive Roller-Clutch can't handle it.

Kingtal0n

Overdrive roller clutch over-runs in 4th gear does not carry any load in fact I think all the sprags over-run in 4th

should be fine to shift to fourth the trick is getting the shifter from 3rd to 4th which pulls off the over-run clutches at the same time the 4th gear clutches come on. Any delay in 4th gear piston apply could transfer load to the roller clutch. So it needs a proper shift modifications and pressure control, 0.125" 4th gear hole maybe even remove the check ball if there is one I forgot, remove accumulation too probably. And keep that force motor current down.

Another option is the kit from sonnax which enables the over-run clutches for every gear selector position even 4th that way when you go from 3 to 4 the only thing that happens is the 4th piston applies and the roller clutch over-runs

vorteciroc

Correct the overrun roller Clutch is Overrunning in 4th-Gear...

It does not have to be Holding to fail... the Input-Shaft and over-drive Planet still have to spin through it.

And when you put too much power through them the the Roller-Clutch will break, seize, or explode.


Ask me how I know.

Fast355

iTrader: (2)

I absolutely believe you. That being said that weakness did not stop GM calibration engineers from upshifting them into 4th gear at WOT a few MPH before the MPH limiter on all of the stock truck and van calibrations I have looked at including the 8.1L. Using the 2002 0411 stock shift tables and stock 110 mph speed limiter, my Tahoe running an 8.1L van tune would go into overdrive at 99 mph and limit out at 110 mph. My L31 powered Express did the same from GM. I looked at a L31 calibration for a 2003 NPR and it was set the same way, ditto for the 6.0L powered vans and trucks. If you could get a NPR to 95 mph it goes into OD and limits at 99 mph. UPS box van or RV with an 8.1L was set the same way as were the TBI and Vortec 454 motorhomes. C5500+ 8.1Ls were governed at 80 mph from GM. The 350 Mexican GMT800 trucks and SUVs go into OD at WOT with either a 4L60E or 4L80E and do not have a speed limiter on them. The 2001 400SS I owned with the L31/4L60E had no problem running 120 mph WOT in overdrive on the stock GM tuning. I was passing a 5.3L powered truck in that unit and he hit his speed limiter at 99, mine grabbed overdrive and ran out the speedo to the peg. Those mexican GMT800 trucks and SUVs are fun trucks. L31 350, 4L60E or a 5spd, 3.73 G80s. Had a 2003 Sonora as well, L31 350, 5spd, 4x4 with 3.73s and factory cat eye front end on a Tahoe.

vorteciroc

I should be more specific when referring to High Power/ High RPM...

I talking more in the realm of 1,000HP and 9,000 - 10,000 RPM.

A stock truck is no issue.
Heavier Vehicles with more Power tend to crack the Over-Drive Planet where it splines on to the Input-Shaft...
A Billet section can be welded on to the Planet to avoid this.

Kingtal0n

I don't see any difference between being in 1st 2nd 3rd gears at 1000rwhp with the trans in D3 where the roller clutch is holding
vs having it shift to fourth to over-run the clutch where it no longer has to hold

There is less stress in 4th than in 3rd on that sprag

If we use this kit for example
https://www.sonnax.com/parts/4496-sm...utch-valve-kit

Then the transmission stays in D4 the entire time. Its not going to get weaker just from over-running a sprag going into 4th, that just takes off stress.

vorteciroc

There is less stress on the Rollers/ Elements as they are not holding the Outer-race...

But there is more stress on the assembly in 4th-Gear, it is at a mechanical disadvantage turning slower than Output-Shaft 0.70:1

Kingtal0n

yeah but the clutch isnt hold anymore. There is no torque applied to the clutch, no stress, it is relieved. The issue is the clutch could blow apart from stress but if it over-runs the stress is gone it just free wheels.

Kingtal0n

Look see no power goes through the roller clutch in 4th it just freespins

Kingtal0n

In third gear the overdrive roller holds you can see the power flows through it

vorteciroc

Yes, I know.
We keep repeating the same things.

In 4th-Gear it Overrruns.
In 3rd-Gear (and every other forward Gear) it Holds.

None the less...
In 4th-Gear with lots of Umph, she go boom!

vorteciroc

Think of it as a Roller-Bearing at this point (It is essentially acting as one)....
I am not talking about the Roller-Clutch Failing to Hold (obviously it is not meant to hold in 4th-Gear)
It Fails like any Bearing that can't carry it's load.
It is simply too small of a Bearing to support the forces placed upon it.

People have experimented with a Larger Sprag (Dog-Bone Style) and had good results.

skinny z

Since we have a couple of knowledgeable people in attendance here, I'll ask a question as it pertains to my own situation. My thanks to the OP for having a thread in the first place.
The transmission is a late edition of the 4L60 before it got it's "E" designation.
I've poured a lot a good parts into this unit only to have something messed up in the process and the transmission ate itself up. Early diagnosis is that one of the clutch packs is fused together. I've one gear in any gear selector position. Except reverse, where it behaves as if using a transbrake.
That said, my question follows the same line as this thread's first post.
The B4C option is supposed to allow OD at WOT. That is if I have my facts straight. Whether the lockup converter is engaged at this point is another matter.
But, regarding the B4C option, are additional mods required to keep the trans alive in OD/WOT?
FTR, this trans self destructed not from my venture in that regard. Development of the car as a whole was curtailed due to a host of issues. None of which are relevant to the question at hand.
Thanks in advance and I look forward to any insights that could be provided. Let's say 500/500 TQ/HP and 6500 RPM.

vorteciroc

Are you saying it will not shift out of 1st-Gear?

Or it is stuck in a different Gear?

With Modifications and aftermarket Parts...
The THM700-R4 can support 1,000+ HP.

The 4L80E can do a good 1,800+ HP.

skinny z

The transmission is always driving the car forward.

Rebuilt about 5000 miles back and during that time, with no WOT action as the engine was hurt, it was the best shifting transmission I'd ever sat behind. 1/2 and 2/3 shifts were like right now! I was stoked.
That was 2017 and I put the project on hold pending a new engine. Fast forward to last fall and I installed the fresh engine. As part of maintenance I dropped the trans pan and found it was 1/8" deep in black sludge. Fine film of metal on the magnet too. This was the original fluid from the rebuild. I was into now so did I a cooler line flush, cleaned things up, added fresh fluid and started the engine break-in process. At first all systems were go although RPMs were kept in check and full throttle shifts were out of the question due to other circumstances. All seemed OK going from 1st to 2nd and 2nd to 3rd while accelerating and coasting getting some load on the rings. It's when I chose to select O.D. and engaged lockup that it was obvious that something was seriously sideways.. While it may have been evident before, it was now obvious that while driving it was trying to engage two gears. At least that was the feeling.

Testing up on stands:
In park, it's trying the draw the engine revs down but my loose converter prevents a stall. No tire movement.
1st, 2nd, 3rd, all forward all the time with no notion of a shift. Had RPMs to 3000 or so trying to put some heat in the engine break-in oil before another change. (And a winter's nap).
Neutral still has a gear engaged. Rear wheels turning and some gear fully engaged.
Reverse is like a transbrake with total lockup.

I've got a new transmission guy on speed-dial and his first thoughts are that the forward clutch is seized (If I recall his thinking correctly). That said, the transmission still hasn't come apart. It's in his shop and the new year will be the jumping off point.
I've a long list of decent parts put into this thing and I'm hoping most can be salvaged with a new core and starting more or less from ground zero.

That's the story.

vorteciroc

Based solely on taking apart other Failed THM700-R4 Transmissions...
(Since I can not look at yours).

Statistically, I would say...
The 3-4 Clutch Pack Burnt up so hot (The Paper Friction Plates go down to Metal) that the Frictions and Steels "Welded" themselves together.
(Essentially the Clutch Pack now can never release).

skinny z

I believe your assessment jives with my builders assessment. He hasn't looked into the innards yet either.
The original builder was a fellow I wasn't acquainted with although a racing friend (who's a notorious cheapskate millionaire) recommended him.
If the transmission hadn't been such a dream at the outset, I would have (and did) overlook the fact that he assembled all my good parts into a Corvette case. Hence no rear transmission mount where it was supposed to be. That's the compromise I was referring to earlier as I DIY'd a rear mount so as to get the car on the road. That was 2017 as I mentioned. Since then the engine failed in a bad way and I've spent the intervening years getting my parts list together and then sourcing a competent machinist. I succeeded in the those two endeavours but the transmission eventually rose up and bit me on the ***.
As my racing friend says, "It's always something!"
Anyway vorteciroc, thanks for looking. And thanks to the original poster for the loan of the thread.

thatsupnow

What are you trying to do?? Why the need of high RPM/HP in 4th gear?? How fast do you need to go??

In my car I've got a boosted 370 with a Jake's lvl 3 rebuild and recalibration kit with a few more goodies in there and I've hit 150 MPH no problem in 3rd around 6800 rpm

skinny z

The original post aside, in my case the Silver State Challenge or Sandhills Open Road Challenge are on my hit list.
With the car set up as it is, I'd say my top speed in 3rd gear (1:1) would be about 118 MPH. I'd need to see 6000 RPM. That's with a 3.73 gear, 26" tire and guessing about 5% converter slip. That's a decent 1/4 mile speed but not terribly fast on 50-90 miles of open highway.
The engine is fully capable of making power north of 6k with peak HP at 6200 and a cam that'll make power past peak. Call it 6500 but despite how well this engine is built I'd not be inclined to keep it there for 10 minutes. But 6500 would see a top speed of 128 MPH in 3rd.
O.D. would net another 30% (physics notwithstanding) and top speed would be 168. Unlikely but considerably quicker.
Lock up the converter and that's another 5%.
So practically speaking approaching 150 MPH, the physics do get in the way and it's probably not possible to get to 6000 in O.D. Further to that, the Yank converter has a single disc clutch so engaging that at maximum TQ isn't the wisest of moves.
That said, I'd need overdrive at .7:1 and about 5300 RPM to see 150. That's doable but a 4th gear is needed.
Probably better suited to a standing mile event although even with O.D. it might be difficult to get to the potential top speed that an open road race would allow. The car was originally built around a cruiser concept with a mix of drag racing and cross country trekking both likely hence the rear gear and O.D. with lockup.

skinny z

@vorteciroc
4L80E notwithstanding, in the days of the 4L60 equipped police cruisers with the B4C option, how was this managed?
Was it the low engine output that kept things in check?
FTR: I've had several 700R4/4L60's and all were modified with the B4C. That said, I can't say, except maybe once on a long lonely stretch of Saskatchewan highway, that I ever had it pinned in O.D.
IIRC, RPMs in overdrive were approaching 6k but I couldn't tell you if the TCC was engaged. Regardless, that transmission went on for many more years of service.
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thatsupnow

Not only can 4th go boom but your driveshaft can turn into a limp noodle if critical speed isn't taken into account when it was built causing more issues than a guy would care to think about

skinny z

Oh yeah. I'm well aware of what an errant driveshaft can do. Or u-joints. The Monte Carlo of one of my racing friends decided to have a u-joint leave the car at speed. The floorpan wasn't happy and thankfully it was the rear joint that let go as that car didn't have a driveshaft loop.

Any performance platform that I've built (largely 3rd gen F- bodies) all get an upgraded 3-1/2" steel shaft and 1350 joints.
The 502 TKO equipped TA got a 4" driveshaft.

thatsupnow

Nice! Mine is a 3" full chromoly built by PST out of Florida

vorteciroc

Yes it was the Low Power Output that allowed things to be.

The RPO: "B4C" Police Package, High-Speed Interceptor, Full-Throttle 4th-Gear Option came down to a single Part Change in the THM700-R4.
The Throttle-Valve Plunger Sleeve Assembly.

In the 1980s, the Transmission Component that allowed for essentially "Full Throttle Up-Shift into 4th-Gear" (Throttle-Valve Plunger Sleeve Assembly) could be purchased over the Dealership Parts Counter...
It came with a warning that stated:
"Not for use with over 250 HP".

If not Observed, usually the 2-4 Band and 3-4 Clutches would Burn-Up...
or the Input-Sprag would FAIL in one way or the other, loosing 3rd and 4th Gear-Selector Positions.