Dink'in with the A518 valve-body

[Ace]

Muhuhhaaa! Eureka!

Okaaaaaay. So tell us, did it take longer to find the pic or fix the prob?!

[BC847]

What did I do? Hmm . . . I don't know.

- In the trans, I left the stiffer springs and spacers (from the TFOD HD kit) in the front and rear band servos. I removed any restrictor plugs used with the SK-TFOD Diesel kit.

I obtained and reconditioned another stock/OEM valve-body.
- I enlarged those four holes in the separator plate associated with the 1-2, and 2-3 shifts.
- On the TV valve, I went back to the stock/OEM spring but did use the ground spool-valve (for delayed up-shift w/part-throttle) ~ nothing to do with drag-racing.
- I used the springs supplied with the SK-TFOD Diesel for the pressure regulator. It's of a two spring design that are set-up so as to provide staged pressure regulation. The softer spring sits a bit longer than the stiffer spring due to a spacer washer. The way I see it, it provides a bit of a cushion with light/part-throttle conditions. I still need to put a pressure gauge on it. The SK-TFOD Diesel instruction wants about four turns for a high power application. I've got it set at 5.5 turns.
- I used the TFOD-HD kit's accumulator piston and springs.
- I used a combination of springs from both kits in the OD accumulator.


As such, the mess shifts quickly with no banging and does not slip with engagement of each gear.


To muddy the outcome, last night I took a couple of loops out of the IP's 366 governor spring as well as a couple of other things. It revs a bit higher with no hint of run-away.

I'm getting a new set of tires tomorrow. Then later that night, I'm gonna make a few passes at the local 1/8 mile track and dial in the OD shift-point.

Then if I like it all, I may end-up down at Rockingham to make a few passes.


We'll see.

[sdubfid]

bc847:

In a drag race does your truck go to 3200rpm then shift and drop rpm and go to 3200rpm again?

From a standing start my truck shifts at 2500rpm and the rpms don't fluctuate until i get into od then they slowly rise to 2700rpm.

Seems to me like I am losing out on 700rpm of powerband. If I have the 3200rpm spring wouldn't it make sense to delay my transmission from shifting until it hits 3200rpm?

What adjustments change the shift point and where should it be set at?

[BC847]

As best I understand the mess, in a WOT condition, the shift points are ultimately controlled by the mechanical governor that's mounted to the output shaft in the tail-end of the OD housing. Ya gotta pull the OD section off and remove the guts to get to the governor. There's a spring in there that in its stock/OEM condition has about an 800lb preload and involves a cage like affair with a press to get it out safely. It's not a big deal but you really need the tool.
Further, with reassembling the guts, one has to align the splines of the clutch disc's/steels so that the mess will slide back into place under the truck. If you've got an old tail-shaft (not sure what that shaft is termed in this app), you can cut it down so as to fit inside the cage mentioned above for easy reassembly.

Having got to the governor one finds it has sliding weights that with increasing shaft speed, the weights shift a little valve deal thus doing its thing.

How much weight to grind? Danged if I know. Haven't been there yet. There's a fella on here that has been there and I can't remember his name.


I'm going to the track tonight and will know for sure where it's shifting though it initially appears I'm right at or a little above where you describe.
What sits in the back of my head right now is the fact that just prior to this most recent tune, the mess was shifting around 3K but was defueling big-time at that point. I cut a couple of loops out of the 366 IP spring the other night in an attempt to fix the defueling. But I also was able to advance the timing a bit since the new IP lines went on. A quick 1st to 2nd blast appears as though the boost is down.

It could be a result of the increased timing. OR I've not got the same fueling I had before messing with it. Shit.

I'll know better shortly.

[BC847]

Well crap.

The track was very busy so I was only able to make two passes.

- The trans shifts just fine with firm transitions ~ no banging. I "Think" it's shifting about 2800. Not sure, only a few seconds to take it all in, and somebody's got to drive.

- I think I incorrectly indexed the throttle or something as power is down: EGT's, boost, and all track times. I'm sure things were assembled as they were removed. See below . . .


Is there a relationship between the fuel screw and the throttle indexing? I'm thinking that my dinking with the governor spring demands I have a hard look at the two. I have all ideas that I basically need to reestablish the base settings of the two as it were.

[dragrdan]

Not so sure on the 518's, but my old 727 homebrew shift kit consisted of removing the 1-2 accumulator spring, and adjusting the line pressure up.
BTW adjusting the line pressure up also ups the shift point. When governor pressure is higher than line pressure is when it shifts. Another benefit of upping the line pressure is applying more pressure to the bands and clutches for better holding power.
Also in trannys that use dexron/mercon I drain it out, and use type F.