Lost first gear in 700R4 - LONG POST

[Beltway]

My truck is used to transport construction tools and materials from Washington, DC to the Catskills in NY every few weeks. It never tows and is rarely loaded with more than, say 800 lbs. The tranny was rebuilt 17,000 miles ago. I installed a manual torque converter lockup switch 4,000 miles ago. The tranny has never been able to downshift from OD without manually doing so. Has always shifted fine.

Truck ran great all the way back from NY last night until I got off the highway close to home. I immediately noticed that it labored hard to get going from a dead stop. After the second time I realized that it wasn't going into first. I found that I could manually drop it into first with the selector, but it wouldn't do it in Drive. Shifts fine when I control it manually.

As a final bit of background, I blew the transmission cooler line off twice in the past month. It didn't run for more than around 10 seconds after it blew off and spewed the ATF all over creation. Always ran/shifted fine after those events.

Anyone have any idea whats wrong and how to fix it?

Thanks!

[john8662]

Hopefully others will chime in with more transmission knowledge than I have. But, the fact remains the transmission wasn't operating properly prior to the failure. The symptom of not shifting down once in OD is a symptom of the TV cable not being properly adjusted or problems with the TV system in the valve body in the transmission.

So were you not getting downshifts in other gears either?

As usual, check your fluid, is it full, is is burnt smeling or dark?

The transmission cooler line situation also sounds suspect, like the lines have been cut during transmission removal, and spliced back together with rubber lines. These lines should be replaced if this is the case, or double hose connections are needed.

[G. Gearloose]

Perhaps something is amiss with the governer

[Lightyear]

Also check the torque converter clutch circuits. Similar thing happened to my '88 'Burb. Had the 700R4 'rebuilt' after the case cracked. About a month later, the TCC started acting funny, cycling in and out of lockup. Finally got to the poiont it locks up in first gear, and will only release if brakes are applied. I disconnected the plug, with the intent of installing a manual switch. Check your wiring set-up to confirm it's only locking up when you set your switch to 'on'. If it feels like a manual tranny that's trying to get started in too high a gear, it might be the TCC.

Buzz

[Beltway]

Thanks all for the input.

Tranny cooler lines are indeed rubber spliced into metal. I had no idea that wasn't stock, to be honest. Have to see what I can do about that.

Agreed re: not operating properly for awhile. Might be worth my while to take this one to a shop. I installed the manual TC lockup switch but thats about all I can do with a tranny. A fella on another forum mentioned that I may have lost one of the pumps due to the blown line. Have to see what the pressure is, once I figure out how to do that.

Far as I can tell, my TC will only lock up in 4th gear due to a switch inside. Don't think thats the problem, as everything feels fine when I manually drop it into 1st. It also performs fine on the highway, going in and out of TC lockup with no problem and never locking up in third.

Again, thanks all for the input. The more the merrier, so please keep it coming. I'll post more info when I've got it.