700r4

[rich ullsmith]

Any 700r4 tranny guru's out there?

Can damage result when using a 700r4 in overdrive when the TCC is not operating? Bought an 87 unit that was, as far as I could see, quite solid.  Was went thru, new converter, shifts great. But the TCC will not engage with the car in gear, and chocked to prevent moving.

Put juice to the correct pin, but nothing. Does it also need to go thru the high gear pressure switch?

[rich ullsmith]

Also, I should have asked: how much slippage am I incurring at 60 mph, @ 1900 rpm? Is that worth 1 mpg? or excessive heat in the converter?      Thanks for the help    Rich U.

[Shark Racer]

Is the new converter a lockup converter?

The 700R4s will not get full fluid flow until lockup, so depending on the size of the vehicle there MAY be trans damage. If you're pulling a lot and the pump is never flowing full, you could easily overheat the fluid and when that happens transmission damage (clutches and whatnot) are soon to follow.

As to how the lockup mechanism works... not too familiar. There are lots of forums that will likely know the answer to that one.

[passthebuck]

I had the same problem this past August on a one year old rebuild. Ended up being the lockup solenoid and was a super easy fix. I diagnosed it by removing the part and putting compressed air to the plunger while checking for continuity at the same time. Take your bad solenoid to a trans shop & they'll sell you what you need.

I too was stressed about hurting my trans because mine failed 60mi into a 120 mile drive. My trans guru said it wont hurt it at all to drive in 4th without the converter locked but it will obviously waste more gas.

Good luck & let us know how it goes.

[rich ullsmith]

Well, it turns out I do not have a lock up converter. The tranny guy says, thru another party, that appropriate steps in the pump have been taken, so it gets fluid everywhere.  In all respects, the trans works great.
So, my final question, (I swear) is: What does the non lock up converter cost me in MPG, and is it worth converting?   I might add, next year I intend to put 15,000 miles on, half on freeways.   Thanks for the help.    Rich U.

[passthebuck]

That's a tough one to answer Rich. 4th on a 700r4 is a 30% overdrive & the lockup, for me, before I changed the rear gears to 3.73 from 3.08 & a 29" tire, dropped the rpms by about 500. It will be more now with the 3.73's but I didn't have time this fall for a test drive. This may be a guesstimate for those that know more than me, but if you're into or close to the secondaries with that extra rpm, then in my opinion, it could save you a fair but of gas, but I cannot say for sure... I'd be talking to my local transmission Jedi if I were you.

[rich ullsmith]

Thanks for the help, guys. I'm still tweaking Cliff's carb, so this tranny thing is not crucial right now. That being said, I don't think there is much more MPG to be had with the lockup. Maybe when I freshen up the motor, the lockup will be on the list
I'm a geezer, so I drive like one and am always "feathering" those primaries. My 3.25 (approx) rear is starting to growl, so maybe a 2.73 can help me lower those RPM's.       Thanks again, Rich

[429bbf]

rich.not sure the taller gears will do you anygood. ive got 2.75 in a 1972 ford ltd with a nicely built 429 with a 800 quad with cliffs parts.at 65mph i can only get about 12 mpg. because my engine is running to slow.about 2300 rpm. when i speed the car up to about 85 t0 90 on the interstate the milage jumps to about 17mpg. im also running about 3000rpm. so im considering dropping the ratio to maybe 3.23 im not sure i havent done the math to see what the rpms would be at 75.oh both runs were done on the same day 100 miles each way. i filled up at each town to get an exact test.i do not have converter lockup the trans is stock with 100000 miles . hope this helps dean

[rich ullsmith]

Thanks, 429~

Am doing the 2.73; it's pristine for being an '84. Will post my results after some testing.   Rich U.

[omaha]

Im not exactly sure how much mpg you would waste but id guess about 2/3 mpg ont the open hyway only. around town not so much. Of course Mr. Ruggles ALSO rote the book on the 700 R4 trans. Very good book also. Excellent info!
The lockup works with hydraulic pressure and a pressure plate and friction disc.