So im putting the Th400 back togeather and my teacher showed me a few tricks in make the trans apply rather hard. Ive streched out the pressure regulator spring about a 1" to make it tigher he said that will add some jerk to the shift, also he said i can flip over the acumulator piston and take the spring out to take away that soft apply, also thinking of removing 1/3 of the springs. I am just curious with the spring streched the acumulator fliped and 1/3 piston springs out how hard with this thing shift i was looking to get a 2nd gear chirp, but i dont want it to pound into gear super crazy. I have a buddy with a 69 chevelle and his trans gives you a nice jerk into your seat at 2nd gear. exactly how crazy of a jerk are we talking about here? Sorry in advance for the clutter this is the best way I can describe it basicly looking for reccommendations and kind of a idea what it will feel like thanks guys. :3gears: GO BULLS
I'm afraid it's going to be a roll of the dice, but it'll definitely hit harder. I can't say anything good about stretching the relief spring...you added a whole inch to it's length???? Shims are sometimes added, but those are measured in thousandths of an inch! How can you quantify the change unless you measure line pressure before & after? There are failure modes associated with excessively high line pressure. Devon
Um i may have the names mixed up but it was the spring on the pump assembly and my teach said it adds a decent amount of pressure. im just trying to gauge if ill need a neck harness while driving
Around here, we call those "safety-shifts". Basically it revs out to motor-exploding RPM, and then shifts . . . good way to break something ou:
Just pull the vaccuum line to the modulator. When my modulator blew the shift from first to second almost ripped my shoulder out of the socket.
At zero vacuum and/or the kickdown switch activated, doesn't the trans then rely on the governor to determine when to shift? Even my Centurion, with the governor forcing the shift at 5200rpm is violent enough that with the 2.93 gears at almost 50mph it will chirp the tire on dry pavement.
Correct. With the modulator seeing zero vacuum, you'll lose part throttle upshifts until you reach a high rpm. Devon
Yup. No shift until max rpm and then the car tries to rip your arms off. Of course if you enjoy your arms you could always let go of the wheel just as it's about to shift :laugh: I ended up with an adjustable modulator. It seems to work well on fine tuning the shift firmness. Right now I have it set to Electra shifting and I have a hard time knowing what gear I'm in because the shifts are so soft and smooth. I'm thinking of bumping it up to the GS shifts just so that I know what the car's doing. Isn't it true that quick hard shifts are easier on the trans than the slow soft shifts? Something about less sliping and less heat o No: By the way the one I'm using is part # MV105 at Autozone
In the Ron Sessions books on the 350 and 400 transmissions, he makes a point of telling the reader that the adjustment on those modulators can be abused by adjusting for very soft shifts. It is possible to lower modulator pressure below factory settings, and that can result in accelerated wear of friction materials because of clutch and band slippage. I'd turn it back.
Back to what? It's in an Electra :laugh: I'm just throwing out the idea of using a modulator to make the adjustments instead of screwing with internal components in the trans.
I'd turn it back so you can feel the shifts:laugh: Yes, the modulator can give you limited adjustment on minimum and part throttle shift point and feel. For full throttle shift points, ya gotta mess with the governor.
I'm not sure on this if he wants only wide open firm shifts or if he wants a generaly firm shift o No:
The accumulator change reduces the cushioning of fluid during the 1-2 shift. This makes for a nice crisp 1-2 shift, as the pressure is not reduced as much during that time. This is what B&M kits offer in the instructions, or at least used to. I haven't put in one of their kits in a while. But I could even get 2nd gear scratch in a Chevy Vega with a B&M kit. Of course, it was a panel truck (no side rear windows, no rear seat, just a storage compartment, 3.36 performance axle and the GT engine). That thing was right quick for a little 4-banger! I don't know about or recommend stretching springs. Stretching a spring exceeds its elastic limit. All bets are off on that tactic, as far as I'm concerned. YMMV
Im aiming for firm shifts but when i really get into it puts you back into your seat. so id guess id go for nice solid firm shifts.
