Will be taking the GS 470 build to the chassis dyno in the new year. I have a JW stall converter on my turbo 400, approximately 3400 stall. I want the tranni to stay in high gear from 3000 rpm to the top end of the dyno pulls without shifting down to 2nd. If i take a governor, weld the inner weights to the outers in the full outward position, will this cause the tranni to shift gears very quickly and prevent tranni from kicking down etc when we do the pulls on the chassis dyno. This query may belong in the tranni section, please move if need be. another thought, weld up weights, remove gear so there is no resistance on valve - will it upshift quickly and just stay in 3rd gear? Thanks
I didn’t know you had to keep it in third gear for the pulls On my GN, I didn’t do anything except 5 gals of race gas, run what yah brung I say
The 3rd gear is the 1 to 1 ratio for the dyno parameters. If your in second gear, it will effect the dyno torque numbers etc. Just want to shift into 3rd and roll into throttle from about 3,000 to 6,000 without any gear changes. I’m no turbo 400 expert, but I think you want the kickdown connected for line pressure etc. With possibility of 575 plus pounds of torque, over 500 hp, want the turbo 400 to use whatever features it has to not allow slippage etc. I believe if a governor is set up to shift low enough, it will just stay in 3rd gear for the pulls, even if the kickdown solenoid is activated.
There are thousands upon thousands of th400s never seen an operational downshift plug. I dynoed my car with the downshift operating...wasn't an issue just run it up over 50mph wheel speed it won't down shift unless the rear gear is super high
Are you going on the chassis dyno for tuning or a hp number? If all your after is a # then yes it needs to stay in 3rd gear.Now depending on the convertor build it may or may not couple completely on the rollers affecting your #.I see it every day on our dyno.I take the number with a grain of salt.we look at the beginning #s and the end number while tuning.The track will tell the truth. Imo leave the trans alone and just tune it and see how it comes out.Be ready for atleast 20% lower #s than you expect depending on the manufacturer of the dyno.As a rule dynojets read higher than a mustang dyno.
I get 2 full days on the dyno. Will be setting up light throttle cruise, of course wot pulls. I have a modified q jet, Holley 850, Holley hp1000 including spacers….so lots to do or try. We’re going to weld up the weights on the governor in the extended position to hopefully cause tranni to upshift quickly, stay in 3rd. We know that on the wot pulls, stall converter will dictate when we start data on the pulls. I’m not expecting any particular hp, agree the track will reflect power. Hoping this combo will get me into the high 11s. Just starting to take accessories off the current stock 455 in the car. Thanks for the input
What fan are you running? If it is a clutch type and if it has the thermostatic coil type remove it and install a standard RPM/centrifugal type only. They are fairly cheap. If you keep the temperature sensitive type on you could start soaking up HP as the engine gets hotter that type will keep getting tighter and tighter. On the chassis dyno I always installed the clutch only type to keep it consistent. Tried removing it at the dyno and ran no fan. Was only using about 9-10 HP. As mentioned just removing the DS wire off the side of the trans should do the trick to mostly keep it from downshifting when they go to WOT in 3rd. I don't think the DS solenoid affects line pressure for the clutches.
Mike, I’m probably running the 20 inch 5 blade I have. It has 2.5 inch pitch, I have a HD clutch for it. Initially not concerned about hp usage as flat tappet cam break in is first priority. As far as the turbo 400, I’ve modified a governor so the valve is in the shift position - welded inner weights to outers, outer weights in the full expanded shift position. We will just shift the tranni manually 1 to 2, then 2 to 3 and in theory will stay in 3rd no matter wot or part throttle cruise.
HP usage isn't the problem as much as HP inconsistency will be. Unless you keep the engine at exactly the same temp the clutch will use different HP levels depending on how hot the engine gets. The clutch you have will be fine for cam break-in but not so good for making changes on the dyno. If the clutch goes from loose to tight it could change HP 5-25 numbers. The clutch I talked about is always the same level of HP usage. That is why lots of bracket racers only use that type of clutch. You don't have to wonder if the clutch will change your ET as the temp changes.
Mike - thanks for the info/experience. I will likely try the non thermo unit on the dyno. Makes sense
