Lockup Convertor Mod on 700R4

[MrMarty51]

1993 GMC 1500 4 wheel drive and TH700R4.
I havent tried it yet but I was wanting a bit of information and input before trying this.I do`nt want to burn out the transmission.
When pulling a grade/hill,kind of an intermediat hill for angel and distance to top the torque convertor unlocks then the transmission kicks down from OD to 3rd and at eighty MPH it sucks quite a bit of fuel and roars quite loud.
On some hills that are not quite as steep the convertor unlocks and holds the pickup at speed without the trans, shifting down.
I am wondering if I hooked a grounding switch to the brake switch so I could unlock the convertor earlier on the steeper hills I think just that slight downshift would hold the pickup to speed without shifting the trans, out of OD.
My main concern would be of it by not shifting out of OD to 3rd if it could possibly starve some of the transmission of fluid and cause it to burn out some bearings or possibly the OD planetaries.
I tried to talk to a transmission rebuild shop in Billings about this and all He would say is dont do it,would`nt say why to not do it even after I questioned Him about it.
Anyone have any comments or suggestions on the subject ????

 

[HotRodPC]

Sounds to me the transmission is working properly as is. The trans is unlocking the TC and downshifting to 3rd for a reason. It's protecting itself. Are you aware it's advised NOT to tow in OD? You don't have to worry about Trans fluid starving so long as your fluid level is correct in the transmission. You have no need to worry about bearings or planetaries, and the OD planets and the same ones used for 1 through 3rd gears. It's just all a matter of which ones are held, and with ones are active that decide the gear your in. What you need to be concerned about burning up is your 3-4 clutch pack.

At 80, they all suck alot of gas. If you want to unlock the converter sooner, just lightly tap the brake pedal and there you go, it's unlocked until it meets the criteria to lock again.

 

[89Suburban]

Holy ****, 80 MPH downshift into 3rd? And towing to boot?

 

[HotRodPC]

Holy ****, 80 MPH downshift into 3rd? And towing to boot?

with a 700r4 even.

 

[HotRodPC]

Oh yeah, I wanted to confirm, this is a 700r4, not a 4L60-E? 93 was first coulda been 4L60-E, actually should be, but I do know some 93 700r4's do exist.

 

[Driver4r]

Holy ****, 80 MPH downshift into 3rd? And towing to boot?

iv downshift to 2nd going 70mph to pass someone. Screemed like a ****.

 

[Jims86]

Dont bother. There is already a brake switch that interrupts the positive side of the system when you hit the brakes. If its lugging too much, just pop it into 3rd manually, and let it run in Lockup 3rd gear.

 

[89Suburban]

iv downshift to 2nd going 70mph to pass someone. Screemed like a ****.

I'm sure it did.

 

[HotRodPC]

My C20 will downshift from 3rd to 2nd and hold it in 2nd to .... not even sure, it's well past 85 mph before it hits 3rd. Speedo is buried at 85, so if I had to guess, maybe 90. BUT, that's with 3.21 gears and 31in tires. I damn sure won't be doing that with 3.73's, 4.10's or 4.56's.

 

[89Suburban]

If I tried that **** in mine I'd be walking back home, lol!!!

 

[HotRodPC]

No OD, and no lock up converter in the K1500. With 3.73's and 31 inch tires, had to speed buried, but it was sure screamin. Glad all the internals in the motors and transmissions is all good though or I might be walking home too.

 

[Driver4r]

I did that when i still had 4.11's

 

[HotRodPC]

I did it many times in my 64 GMC with 4.56's and 31in tires and that speedo was 100mph. But, that motor loved 6000-6500rpm. I'd get it up there around 5500 and buddies were putting their legs up in the seat thinking it was coming apart thru the floorboad. They really **** themselves, when I'd hold it down in 1st at 6200-6500 and go for 1/2 mile or so before I hit 2nd. I never seen such big eyes staring me down, like WTF? I just laughed my ass off. They always told me I was gonna blow that fugger up. Nope, NEVER DID !!! I built it, I knew what was in it. And it was a 2 bolt main.

 

[Paulscrawler78]

I did it many times in my 64 GMC with 4.56's and 31in tires and that speedo was 100mph. But, that motor loved 6000-6500rpm. I'd get it up there around 5500 and buddies were putting their legs up in the seat thinking it was coming apart thru the floorboad. They really **** themselves, when I'd hold it down in 1st at 6200-6500 and go for 1/2 mile or so before I hit 2nd. I never seen such big eyes staring me down, like WTF? I just laughed my ass off. They always told me I was gonna blow that fugger up. Nope, NEVER DID !!! I built it, I knew what was in it. And it was a 2 bolt main.

Sounds like my 69-72 c10 I had years and years and years ago it used to be an agricultural truck for FSU I paid 100.00 for the truck and built a 650hp 350 4 bolt main with a Muncie 4 speed dropped to the ground with 15" rear rubber Lol with a Eaton spool and 4:10s or what ever they where did burn outs through all 4 gears if I stayed in it Lol and it looked like someone rolled it over a few times and it ran like a rapped ape lol

 

[HotRodPC]

Sounds like my 69-72 c10 I had years and years and years ago it used to be an agricultural truck for FSU I paid 100.00 for the truck and built a 650hp 350 4 bolt main with a Muncie 4 speed dropped to the ground with 15" rear rubber Lol with a Eaton spool and 4:10s or what ever they where did burn outs through all 4 gears if I stayed in it Lol and it looked like someone rolled it over a few times and it ran like a rapped ape lol

I could do that too thru all gears in my Muncies, til I broke my M22 for the final time, then I went to Auto's. Autos are so cheap, you can afford to break one once a year, as in a Th350. Th400 usually lasted a few years though. 700r4s