700R4 Information Thread

[NickTransmissions]

Thought Type F was for Ford? It might be Dex6, I'd need to dig out the jugs.

I don't have the tools to do a pressure test. I don't see how a fluid change can stress the clutch pack when it was fine not 6 hours before and I don't smell burned fluid before or now.

Type F is a Ford formulation. Has slightly different friction modifiers compared to the Dextron stuff.

 

[Ricko1966]

Is Mercon V the equivalent to the old type F fluid?

The guy that ran the trusty trans shop I used to go to, told me about 25 years ago that I could use it to slightly firm up the shifts. Similar to running the B&M Trick Shift fluid.

B&M told me to run type F in my th350. I can't remember exactly what the situation was, but I called them had them on the phone,their tech guy told me run type F so I have forever since.

 

[grummy]

vacuum switch on the firewall

No, that switch is the Tip-In for the ESC ignition control. The Vacuum switch for the lockup is just above and to the left of the Brake Booster. That switch in my truck cuts out the lockup the second vacuum goes high, like when you let off the gas. I think when I measured when mine switched, it was like anything above a few inches (4-5 maybe, I forget). My truck practically feels like it freewheels when I let off the gas, though I have a 2.73:1 rear.

 

[grummy]

You are saying the TCC should lock up in 4th and 3rd automatically or just 4th?

I've found a lot of differing info about this.... My 1983, with a 1989 G20 700r4 will lock in 2nd, 3rd and 4th. I have a push button switch on my shifter, connected to a latching relay to disengage it unless I want it.

 

[NickTransmissions]

I've found a lot of differing info about this.... My 1983, with a 1989 G20 700r4 will lock in 2nd, 3rd and 4th. I have a push button switch on my shifter, connected to a latching relay to disengage it unless I want it.

1982-E84, many 700R4s had a TCC apply strategy that included 2nd gear. You can tell, broadly speaking, how the trans was set up by counting the number of pressure switches on the valve body. While there were some variances over the course of the 700R4's production lifecycle, generally speaking, the TCC was set up to apply in 2nd-4th in 82-E84; 3rd and 4th L84-93.

Again, there were some exceptions to this generalization.

 

[1979 K10]

No, that switch is the Tip-In for the ESC ignition control. The Vacuum switch for the lockup is just above and to the left of the Brake Booster. That switch in my truck cuts out the lockup the second vacuum goes high, like when you let off the gas. I think when I measured when mine switched, it was like anything above a few inches (4-5 maybe, I forget). My truck practically feels like it freewheels when I let off the gas, though I have a 2.73:1 rear.

I’ll have to double check but that vacuum switch next to the brake booster has had no vacuum to it for a long time. Vacuum line from manifold to that switch has long rotted away. So with that switch getting no vacuum my torque converter lockup was always engaged?

 

[grummy]

I’ll have to double check but that vacuum switch next to the brake booster has had no vacuum to it for a long time. Vacuum line from manifold to that switch has long rotted away. So with that switch getting no vacuum my torque converter lockup was always engaged?

U'mmm, well, if it was not disengaging,, or, always engaged, you would know it ! It'd be like pulling up to a stop sign and never throwing the clutch in on a stick. So, even without that vac switch working, you still have something else not allowing it to engage.

I forget already all the things involved with mine when I was digging thru it.. Mine also had something called an EGR Bleed included in the circuit for the lockup. Not positive sitting here, but I think I found that my lockup would engage if I applied 12v to the yellow wire at my EGR bleed. I think it is the same yellow running down to the trans plug, but was easier to connect my disconnect relay using the wires there.

 

[grummy]

1982-E84, many 700R4s had a TCC apply strategy that included 2nd gear.

Thanks for the information !

I can tell you that I find it annoying to engage in second, and I'd have no clue how to stop it from doing so. This baby gets into second and pretty much immediately goes to lock up right after. This is why I put a relay in so I can have it applying the clutch or not. I generally don't lock it driving around town.

Years back, I had a boss that always bought a new truck every year during that 1981-1988 time period. I never noticed, or do I recall any of those trucks doing a lockup in second, and, I owned numerous 80-86 G20 vans that didn't do it either. But hey, It's a $300 used trans I put in to get it on the road and it does do that !

 

[Ricko1966]

Thanks for the information !

I can tell you that I find it annoying to engage in second, and I'd have no clue how to stop it from doing so. This baby gets into second and pretty much immediately goes to lock up right after. This is why I put a relay in so I can have it applying the clutch or not. I generally don't lock it driving around town.

Years back, I had a boss that always bought a new truck every year during that 1981-1988 time period. I never noticed, or do I recall any of those trucks doing a lockup in second, and, I owned numerous 80-86 G20 vans that didn't do it either. But hey, It's a $300 used trans I put in to get it on the road
and it does do that !
.

Make sure you have a working vacuum switch to interrupt torque converter solenoid,if it's working change it to one with a different pressure. You want the switch to break the circuit to the torque converter solenoid at vacuum levels less than cruise

 

[NickTransmissions]

Thanks for the information !

I can tell you that I find it annoying to engage in second, and I'd have no clue how to stop it from doing so. This baby gets into second and pretty much immediately goes to lock up right after. This is why I put a relay in so I can have it applying the clutch or not. I generally don't lock it driving around town.

Years back, I had a boss that always bought a new truck every year during that 1981-1988 time period. I never noticed, or do I recall any of those trucks doing a lockup in second, and, I owned numerous 80-86 G20 vans that didn't do it either. But hey, It's a $300 used trans I put in to get it on the road and it does do that !

Agree, I'm not a fan of TCC apply strategies that include lock up in earlier gears...I'd prefer it to lock in fourth only but GM engineers where trying to squeeze every last ounce of fuel economy out of those cars/trucks back then...They repeated the same strategy with the six speeds...The 6L transmissions (6L45,50,80,90) all have the TCC active between 2nd and 6th gears; most 6L transmission tunes defeat the lock up in all gears except 5th and 6th.