If you don't have a manual valve body, that is.

I went racing Friday night, car performed beautifully, I had trouble getting a green in TT's, but got it together for eliminations. Won 4 rounds before bulbing to the eventual winner.

Drove home, parked the car, got ready for racing again today and headed for the track about 9:30 a.m. As I pulled out of the neighborhood, the tranny wouldn't shift out of 1st. I stopped and checked the vacuum line, it was fine. For some reason I thought it might be a little low on fluid so I'd let it warm up on the way to the track and check it there. As I pulled up to the gate, I finally got the message that the modulator wasn't.

1st TT, it shifted okay since I shift manually, but the ET and MPH were down. Duh, the leaking modulator will lean out #8, since the vacuum is tapped off that runner. Plugged it, 2nd TT was horrible because 60' was off but MPH and splits were back where they should be - I had backed it farther into the water that time, while the 1st one was almost a dry burnout. We had a long wait before elims, was lounging and talking about it with a bud who had watched my 2nd TT, he thought my burnout was pretty short & weak - I thought it was actually longer, finally realized that it hadn't shifted to 2nd during the burnout - duh #2.

So, by modifying my burnout for elims I managed to go some rounds. The return road was interesting, had to get it up to 40 mph to get it to shift to 2nd, the speed limit on the return road is 20...

The real kicker is I had another modulator sitting on the bench in the garage.

 

Hehe, yeah sorta found that out too when mine wasn't plugged into a good vacuum source. Shift points where all screwed up till plugging it into where I had it before. btw, looks like I'll be going to the track possibly on the 12th Going to be the first time out with the new motor. Speed limit on their return is 5 mph

 

With the TH400 lets not forget the importance of the govenor which also produces similair results. The nice thing about 400's if your just footing braking and bracket racing you can dail it to shift itself by grinding on the govenor itself. I know plenty of guys running this brute that leave the shifer in first gear all the way down the track but have the govenor tuned to shift anywhere from 5-6500 by itself and it is very very consistent.

We found out one thing after 2 valve body swaps on my freinds TH400 that was doing a great 1-2 shift but sluggish 2-3, actually more like a factory slow/slipping 2-3 shift. Found out the case behind the govenor was worn and leaking pressure. Took a 2hr road trip to do bench top pressure testing, a very experienced tranny guy and on the phone conversations to BTE to track down that little booger.

But like you said 5kid, the modulator can do some very funny things too. Great tranny for racing, but it also has it's flaws unless you set it up for pure racing.

 

Several people said, "Just shift it manually." Well, that's what I do running the 1/4, but unless the engine speed is above the govenor speed, it won't shift.

I know a few people who adjust the govenor to shift so they leave it in drive at the track. I don't like that idea, because if something is causing the engine to sputter below shift speed, you're dead. At least if the govenor shifts the tranny earlier than you want normally, you can shift it at a lower RPM in special circumstances.

 

Jacked the car up this evening to replace the modulator. Should be a quick job, you know - metal line connected to the mod by a short piece of rubber hose, one bolt, one o-ring.

First thing I see when I crawl under there is the hose is bent at a 45 degree angle, and there's a nice little split at the outside of the bend.

The hard line is now curved so it points straight into the modulator, and the rubber hose that connects is not at all bent.

Checked to see if the modulator holds a vacuum - no problem.

How embarrassing...

 

At least it was an easy repair

 

Which means I could have turned around and fixed it before going to the track, or fixed it at the track if I had just jacked it up and looked at it then.

Oh, well, all's well that ends well, they say. :lala: