Turbo350 w/shift kit slamming 2nd gear

[Matt69olds]

The ONLY time I will spend money on a shift kit for a 350 trans is if it’s still in the vehicle and in good working condition. As nick pointed out, it’s very easy to install a homemade shift kit during an overhaul with the things most gearheads have in their shop. The only advantage to a shift kit install with the transmission still in the vehicle is the ability to dual feed the direct clutches.

TransGo is very conservative on recommendations for drilling the spacer plate. Since they have no idea what the intended use will be, or other modifications, it’s far easier to drill a hole bigger than to make it smaller. If I remember correctly, TransGo recommends drilling the feed holes to .125 (1/8 inch) while B&M says to go .185 (3/16). B&M also instructs you to eliminate a few check balls. If you further compare the TransGo to the premium TransPak, you will find the instructions are identical other than check ball/hole sizes.

Many years ago I had a friend who bought a 79 Camaro with a stout 400 engine. That car had a ridiculously violent transmission. It would chirp tires regardless of throttle position, the only thing that changed was how much rubber it would leave on gear changes.

He broke a few intermediate roller clutches. After the 3rd direct drum swap I decided to figure out how to tame the shift. Turns out whoever manufactured the shift kit designed the spacer plate with no feed to the 1-2 accumulator, combined with 3/16 feed holes and the bare minimum check balls.

That transmission might have been ok with a really loose converter, or a race only application but was way to aggressive on the street.

 

[NickTransmissions]

The ONLY time I will spend money on a shift kit for a 350 trans is if it’s still in the vehicle and in good working condition. As nick pointed out, it’s very easy to install a homemade shift kit during an overhaul with the things most gearheads have in their shop. The only advantage to a shift kit install with the transmission still in the vehicle is the ability to dual feed the direct clutches.

TransGo is very conservative on recommendations for drilling the spacer plate. Since they have no idea what the intended use will be, or other modifications, it’s far easier to drill a hole bigger than to make it smaller. If I remember correctly, TransGo recommends drilling the feed holes to .125 (1/8 inch) while B&M says to go .185 (3/16). B&M also instructs you to eliminate a few check balls. If you further compare the TransGo to the premium TransPak, you will find the instructions are identical other than check ball/hole sizes.

Many years ago I had a friend who bought a 79 Camaro with a stout 400 engine. That car had a ridiculously violent transmission. It would chirp tires regardless of throttle position, the only thing that changed was how much rubber it would leave on gear changes.

He broke a few intermediate roller clutches. After the 3rd direct drum swap I decided to figure out how to tame the shift. Turns out whoever manufactured the shift kit designed the spacer plate with no feed to the 1-2 accumulator, combined with 3/16 feed holes and the bare minimum check balls.

That transmission might have been ok with a really loose converter, or a race only application but was way to aggressive on the street.

Yep, Transgo starts out a good bit smaller in diameter for the 1-2 and 2-3 orifices compared to B&M so folks can 'work up' gradually...I like to direct people new to the process to Transgo's info as it let's them get to their final hole sizing while reducing the likelihood they'll go too far and need to either peen or replace the plate. Most won't have a drawer full of extra, untouched ones they can just grab from like we do.

For very high stall street/strip or full race that keep the auto-forward shift pattern, I omit all check balls but the modulator check ball and block the 2-3 feed and 1-2 acc but it's rare I get one requiring that and have never done it for a daily driver.

 

[Hunter79764]

I've got nothing to add here, except that THIS is what good forums do. Solved a problem for the OP, and the rest of us get to learn the why behind some of the industry knowledge etc. I've heard "B&M is too harsh", "Just get a Transgo", and "eh, it ain't needed if your transmission guy knows what he's doing" but never why that is. Thanks for the education!

 

[Ricko1966]

Yes, I didn't mean to question you about the detent cable or suggest that it may be part of the OP's problem, just simply point out that it can have a minor effect on road speed at which the trans shifts. And only at full throttle.

So is it safe to leave out the 1-2 accumulator spring on an an otherwise stock th350? I only ask because my Chevelle has a very powerful sounding exhaust (although the car is far from powerful, lol) that sounds out of place when the trans simply glides into 2nd gear. A more positive shift would match the sound better.

Sorry about getting a little off topic.

Leaving the spring out will make very harsh upshifts,you can get different springs,so it's an all or none situation.

 

[NickTransmissions]

Leaving the spring out will make very harsh upshifts,you can get different springs,so it's an all or none situation.

Rick, I'm assuming you meant to type "can't get"with respect to different tension 1-2 acc springs? If so, that is correct to the best of my knowledge

 

[Ricko1966]

Rick, I'm assuming you meant to type "can't get"with respect to different tension 1-2 acc springs? If so, that is correct to the best of my knowledge

Yep I should learn to proof read. Thanks.

 

[MikeB]

THIS is what good forums do. Solved a problem for the OP, and the rest of us get to learn the why behind some of the industry knowledge etc. Thanks for the education!

I'll second that! Always wanted to rebuild one myself, but never got past the valve body, modulator, and playing with the governor.

My truck's original TH350 is working well and doesn't leak, so I have no excuses to play with it!

BTW, the trans fluid and filter were changed more than 10 years ago, probably around 10K miles. The fluid is still pink, so is there any need to change it? It's a function of miles, not years, right?

 

[AuroraGirl]

Does your converter have a stock-level stall speed?

If so, im not surprised that the 1-2 shift is super harsh as it was set up for that much higher 3500 stall. Check the 1-2 accumulator to see if the spring was omitted. If so, install a new spring and that should tame it. If the spring is installed, you're dropping the valve body and looking at check balls and spacer plate hole sizes...dont keep driving it like it is now, you may crack the outer race on the intermediate one-way clutch and lose 2nd gear all together.

how about modulator concerns?

 

[AuroraGirl]

I'll second that! Always wanted to rebuild one myself, but never got past the valve body, modulator, and playing with the governor.

My truck's original TH350 is working well and doesn't leak, so I have no excuses to play with it!

BTW, the trans fluid and filter were changed more than 10 years ago, probably around 10K miles. The fluid is still pink, so is there any need to change it? It's a function of miles, not years, right?

what kind of fluid is in it and how old is the modulator?

 

[NickTransmissions]

how about modulator concerns?

Read post 10 and all my replies afterward. Modulator is irrelevant in this particular case.

what kind of fluid is in it and how old is the modulator?

Doesnt matter in this case

 

[AuroraGirl]

Doesnt matter in this case

i wasnt asking you that lol. I was asking mike b
based on hiss answers i was not going to recommend a shift kit to him, I was going to recommend a fluid change depending on his answer.

if it was old mineral oil atf like that would have came with it , sure a change isnt a bad idea to keep those best properties in the fluid while its still clean

But if it was a synthetic which was very available in 2014, then I would say leave it

 

[NickTransmissions]

i wasnt asking you that lol. I was asking mike b
based on hiss answers i was not going to recommend a shift kit to him, I was going to recommend a fluid change depending on his answer.

if it was old mineral oil atf like that would have came with it , sure a change isnt a bad idea to keep those best properties in the fluid while its still clean

But if it was a synthetic which was very available in 2014, then I would say leave it

Dex/Merc is perfectly fine in the older GM transmissions; Dex6 wouldn't hurt but it's usually not worth it unless racing/super heavy duty towing hauling. Since the fluid is 10 years old, I'd probably change it but Dex6 isn't critical in this case.

You also quoted my posts and asked me about modulator concerns, which is the same thing another member recommended to look at. However vacuum modulator problems present with different sets of drivability symptoms than what the OP was describing, which was a super hard, late 1-2 upshift but no other issues.

 

[AuroraGirl]

Dex/Merc is perfectly fine in the older GM transmissions; Dex6 wouldn't hurt but it's usually not worth it unless racing/super heavy duty towing hauling. Since the fluid is 10 years old, I'd probably change it but Dex6 isn't critical in this case.

You also quoted my posts and asked me about modulator concerns, which is the same thing another member recommended to look at. However vacuum modulator problems present with different sets of drivability symptoms than what the OP was describing, which was a super hard, late 1-2 upshift but no other issues.

no i was saying if he had used dex 6 in 2014 ish i would say go ahead and leave it in , 10k and 10 years is nothing on it. But if its old style then go aheadm so the fluid keeps its best cleaning and lubricating properties and doesnt have that icky varnish that a lot of old un-rebuilt trans will have

And yes I appreciated your reply I was just curious about how that interacts and I see

Do you do much with fwd transaxle

 

[AuroraGirl]

Dex/Merc is perfectly fine in the older GM transmissions; Dex6 wouldn't hurt but it's usually not worth it unless racing/super heavy duty towing hauling. Since the fluid is 10 years old, I'd probably change it but Dex6 isn't critical in this case.

You also quoted my posts and asked me about modulator concerns, which is the same thing another member recommended to look at. However vacuum modulator problems present with different sets of drivability symptoms than what the OP was describing, which was a super hard, late 1-2 upshift but no other issues.

and I think my 2005 4l80e issue is resolved. I dont have harsh shifts when driving now. But i did mistake the shift count because of the TCC lockup so it was the 2-3 not the 3-4
only thing I did was reset the TAPs and drive it some (the truck had recently been serviced new fluid and filter)

I have a MAF code so i am going to investigate but im surrprised its shifting smoothly with that. Live data doesnt seem logical (seems skewed way too high)

do 4l80e have a 2nd gear start feature? if ou shift to "2"

 

[bucket]

Do you do much with fwd transaxle

I'm glad you were brave enough to ask. I've been too afraid to ask about 440t4 rebuilds, lol.