69 stock TH400 still shifts pretty soft

I installed the B&M shift improver kit on my stock TH400 80k mi wildcat . I followed their instructions for "stage 2" Street/strip option.... It didn't seem to make any notable difference in shift firmness at wot.

I used the same kit and procedure w my stock 72 GS TH350 years ago and shifted MUCH more firm at wot.

Transmission shifts as new and internals show almost no wear. I just wanted to improve the super soft shifts to enjoy driving experience a bit more. I was just very surprised that it didn't make a huge difference like it did in the GS. Any thoughts why no noticeable improvement?

 

I thought if you drill the plate larger.
It shifts more abruptly.

Maybe, check what size your separator plate is ?

 

Try running Type F fluid, it will help a little.
Patrick

 

Thanks. Yes I drilled hole a and b to 11/64 or .172 so should be plenty big?

Haven't thought about type f

 

There used to be a really good thread on here about someone who was rebuilding their TH400. The thread included step by step pictures. What made the thread so invaluable was the tips that some of the Buick trans rebuilding experts added. Included were some directions (with pictures) on improving shift feel without going the shift kit route. Unfortunately, I can't seem to find it right now.

 

Thanks. I think i drilled for range 3.

Google agrees: As to ATF, no problem mixing Dexron and Type F, one can actually fine tune shift harshness as Type F is in fact "grippie"

Maybe half and half?

 

What torque converter is in it? That can affect the shift feel. In a heavy car, it will be less apparent than the lighter GS.

 

Remove the accumulator spring in the valve body and under the big 6 bolt cap on the case

 

Here is the thread I was thinking of......https://www.v8buick.com/index.php?threads/official-66-sp-400-buildup-thread.69003/

 

Stock converter.

 

I did valve body accumulator. I didn't take other cap off. What does removing spring do here?

 

Thanks I'll read before bed

 

I'd throw the B&M stuff in the trash and buy a Trans-Go brand shift kit. I little more money for a lot more value.

 

I don't really want it to bang gears just a little more intentional feel..... Still bewildered why it didn't change dramatically like my GS. I suppose I should be happier that it works flawlessly.

 

Same of the other...the one you removed is the 2/3 accumulatorcushion spring........
The other is the 1-2

Have you checked line pressure if pressure is low it will shift soft

Did you remove any of the check balls??? Some kits have u remove some some don't, I have list of what I've found works great at the shop

Too much clutch pack clearance can also cause soft spongey shifts

 

I saw a recommendation to use a stiffer spring for the reverse low rear accumulator held by the six bolts.

I don't know how or have tools to check line pressure.

 

If you toss a "Shift Kit" plate in the valve body and maybe dick around with the high pressure regulator spring and see no change, you need to stop and realize, unless you go through the entire transmission, setting up all four drivetrain clearances, setting clutch pack clearances, doing the math to add as many clutch (friction) plates, using the best clutch pistons, mods to accumulators, valve body, center support, lube circuit, rollerizing thrust bearings, spool mods, governor, vacuum modulator, 36 element sprag, steel drum, 4L80E forward hub and several other things, you are just going to be unhappy at best, and destroying a transmission, at worst.

It's like anything else. Learn and understand, apply as required for your application.

 

If u put stiffer spring into any accumulator in any trans it will make the shift shifter and slower. Stiffer springs take more pressure to compress......meaning it will take longer to fill equaling slower softer shifts.

You can buy a gauge.......your wanting to do diy tranny stuff but don't have the tools to do so.......not sure what to tell you there. Ppl can give you information, but to diagnose a problem so.etines requires tools.

The holes drilled that big should be providing plenty of fluid to shift well,.....that's the same size I drill mine on my race trans and it shifts very very firm and fast.

The reason I asked about reading the actual pressures is because 100%everything relays on it. You have the stuff that alot of ppl do and most have great results......yours are not......so now we need to look somewhere else farther down the line.


Low pressure could equal worn pump or internal leaking somewhere

 

How many of the 6 check balls did you reinstall?