Adjusting Shift Points?

TheBigO · 06-29-2009, 10:10 PM

My question is-Can you adjust the shift points on a TH-400 trans. If so....how? Your answers is highly appreciated

My transmission is a BOP TH-400 automatic with a 2,200 rpm stall, no shift kit.

jd79ta · 06-29-2009, 11:39 PM

A cheap and simple way to make the car rev more before it shifts, if that's what your after. What I did on my gmc, that had TH400, I bought a new "modulator" I think that's what it's called someone can correct me, that was adjustable, some are adjustable stock. Just pull the little vacum line off the trans and turn the tiny screw in for higher rev's out for earlier shifts. You just need a small slotted screw driver. I believe you can replace the spring behind the mod. to adjust the shifts as well, but I didn't bother with that even with the shift kit I installed, it came with springs, and I left them out which is how it already was anyay.

mkube396 · 06-30-2009, 05:03 AM

get a adjustable modulator

P.S your runing a turbo so i dont know how you would get vac to the trans?

matt69cutlass · 06-30-2009, 06:42 AM

You can make small changes with a adjustable modulator (2-4 mph) if you need to move the shift points more than that you'll have to change the govenor.

jd79ta · 06-30-2009, 07:14 AM

Quote:

Originally Posted by matt69cutlass

You can make small changes with a adjustable modulator (2-4 mph) if you need to move the shift points more than that you'll have to change the govenor.

Not sure how much difference in mph it makes but as for the rpm, it's quite a difference, I probably added esily 500rpm more to the shift points at light acceleration could of went more but I settled it at around 2000rpm.

I actually did the same thing with my T/A, I set it to shift around 1800, it already had an adjustable one in it, I just had to turn the screw.

mkube396 · 06-30-2009, 08:10 AM

govenor only controls the Trans shifting at WOT not part.

TheBigO · 06-30-2009, 11:17 AM

Quote:

Originally Posted by jd79ta

A cheap and simple way to make the car rev more before it shifts, if that's what your after. What I did on my gmc, that had TH400, I bought a new "modulator" I think that's what it's called someone can correct me, that was adjustable, some are adjustable stock. Just pull the little vacum line off the trans and turn the tiny screw in for higher rev's out for earlier shifts. You just need a small slotted screw driver. I believe you can replace the spring behind the mod. to adjust the shifts as well, but I didn't bother with that even with the shift kit I installed, it came with springs, and I left them out which is how it already was anyay.

You just read my mind! Yes! I want my engine to rev more before it shifts.......and I didn't know there was a adjustable modulator for it....where can I buy one for a BOP TH-400.

TheBigO · 06-30-2009, 11:38 AM

Quote:

Originally Posted by jd79ta

A cheap and simple way to make the car rev more before it shifts, if that's what your after. What I did on my gmc, that had TH400, I bought a new "modulator" I think that's what it's called someone can correct me, that was adjustable, some are adjustable stock. Just pull the little vacum line off the trans and turn the tiny screw in for higher rev's out for earlier shifts. You just need a small slotted screw driver. I believe you can replace the spring behind the mod. to adjust the shifts as well, but I didn't bother with that even with the shift kit I installed, it came with springs, and I left them out which is how it already was anyay.

Simply adjust the screw inside the vacuum nipple for more or less diaphragm preload??? counter clockwise or clockwise to rev more before shifting......I am not sure if mine is adjustable if its a stock one...my trans is a remenfactured TH-400 I bought from advance autoparts 3 years ago....the only mod was the deep derale trans pan and filter magnet

425 Racer · 06-30-2009, 04:40 PM

They make a kit for the govenor to shift at higher rpms (B&M I think) with springs and weights.

jd79ta · 06-30-2009, 07:13 PM

Quote:

Originally Posted by TheBigO

Simply adjust the screw inside the vacuum nipple for more or less diaphragm preload??? counter clockwise or clockwise to rev more before shifting......I am not sure if mine is adjustable if its a stock one...my trans is a remenfactured TH-400 I bought from advance autoparts 3 years ago....the only mod was the deep derale trans pan and filter magnet

You turn CW "in", to get more rev, CCW "out", to shift sooner, doesn't matter if its BOP or chevy, they'll work, my TH400 didn't have one stock, it cost me like $20 about 5 years ago, if IIRC. My TH350 in the T/A was an adjustable already.

TheBigO · 06-30-2009, 10:13 PM

Quote:

Originally Posted by 425 Racer

They make a kit for the govenor to shift at higher rpms (B&M I think) with springs and weights.

How hard is it too remove the stock valve modulator and replace it with a adjustable one?

jd79ta · 06-30-2009, 11:57 PM

The modulator and the govener, are two different things, the mod, very easy, it's set up like a distributer, just shoved in and there's a hold down tab, very easy to remove/replace. The gov. is different, not 100% sure about the TH400, but on the 350, it's a cover with a clip over it, but the cover is usually pretty well stuck on there, and it's a pain to get on, unless you have the tranny out of the car then you can just tap it in, I tried to do mine on the car, and had a hard time getting the cover back on, I even put it in the freezer too hopefully shrik it a bit, but still had to tap it on. Aside from the cover, the govener is really easy itself to take out and put it, and the springs can be replaced without taking it apart completely.

RocketV8 · 07-01-2009, 02:02 AM

TheBigO - what are your current shift points? At part throttle and WOT.

425 Racer · 07-01-2009, 05:32 AM

Sorry but the modulator will be a better deal for what you want to do.

RocketV8 · 07-01-2009, 05:47 AM

Quote:

Originally Posted by mkube396

govenor only controls the Trans shifting at WOT not part.

The governor directs fluid flow to the shift valve(s) based on output shaft speed (road speed). The modulator directs fluid flow to the shift valve(s) based on manifold vacuum (engine load) but to the opposite side of it, thus delaying the gear shift. The governor definitely plays a role in shift points both at WOT and part throttle.

TheBigO · 07-01-2009, 10:42 PM

Quote:

Originally Posted by RocketV8

TheBigO - what are your current shift points? At part throttle and WOT.

I just found out that my modulator is adjustable....I removed the vaccum hose...... inserted a thin flat head screw driver.....and turn clockwise.....it felt like I was turning a small screw driver....I only turn it only 1/4 for now....I will take for a spin in the morning too see how the shifting feels...As to answer your question....my shifting feels weak....I mean...I don't feel a cripy shift....I would like too have more cripy shift....though of pouring in F-type fluid in my next transmission filter change....for a more crisper shift.

The whole reason for this.....I would like to have my engine rev a little more before it shifts....I notice my turbocharger spools alot faster.....at 2,500rpms instead at 3,100 rpms.....I am not sure why?? But it does for some reason.

jd79ta · 07-01-2009, 11:05 PM

Quote:

Originally Posted by TheBigO

I just found out that my modulator is adjustable....I removed the vaccum hose...... inserted a thin flat head screw driver.....and turn clockwise.....it felt like I was turning a small screw driver....I only turn it only 1/4 for now....I will take for a spin in the morning too see how the shifting feels....

You gotta turn a quite a bit to get a real difference, you might need to go 3-4 turns (complete turns), depending on how much change you want. I know I went a couple turns.

matt69cutlass · 07-02-2009, 05:37 AM

I didnt notice the engine was turbocharged, that changes things. You cant adjust the modulator with a turbo, the reason being the modulator reads VACUUM. Under boost the trans thinks your at WOT. Your going to need a mechanical modulator, I know B&M use to make one. If you cant find one your other option is a manual valve body. I can provide a kit to convert your valve body if your interested in going that route.

TheBigO · 07-02-2009, 08:29 AM

Quote:

Originally Posted by matt69cutlass

I didnt notice the engine was turbocharged, that changes things. You cant adjust the modulator with a turbo, the reason being the modulator reads VACUUM. Under boost the trans thinks your at WOT. Your going to need a mechanical modulator, I know B&M use to make one. If you cant find one your other option is a manual valve body. I can provide a kit to convert your valve body if your interested in going that route.

So you are saying that my TH-400 will go into 3rd gear fast? That intersting how come STS turbocharger, HP turbocharger, Procharger Supercharger, Vortech supercharger, and Paxton Supercharger companys don't meantion this too to there custmers when they are selling there basic 5-6 psi kits on there older engines with automatics? Any who....here a link of a vid for my olds

http://videos.streetfire.net/video/T...psi_649505.htm

matt69cutlass · 07-02-2009, 09:02 AM

Do you have access to a hand held vaccum pump? If so try this. Appy 10 inches of vaccum to the modulator, see how it shifts. Apply 5 inches, test drive,try 15 test drive and so on. Hopefully you can see a pattern develope,more vaccum=early shifts, lower vacuum=later shifts. Im not sure why the turbo manufacuters dont mention trans modifications, maybe if you talk to them they will have another solution. Anyway Im pretty sure a TH 400 trans modulator wont work correctly with a turbocharge engine. As soon as the engine starts to build boost the trans will think your at WOT. Hope that helps.