Plugging the 1-2 accu feed hole.

[DorianL]

I have been reading some back threads of mine (was surprised what I found there) as well as others' experiences...

I am a bit frustrated with my 1-2 shift. It is firms up till about mild half throttle (I am lucky if it chirps) and then seems to become less noticeable as I really get on the gas.

I drive a 3750# beast with 500HP at 5500 and 600TQ at 3000. The 200-4R innards are: wide band, big billet servo, everything properly clearanced, shift Kit, D5 converter.

This seems to be an ideal candidate for plugging the feed hole. I want (like everyone else?) tire-shredding 1-2 shifts at WOT, chirppy shifts at power and crisp shifts at loafing.

What say you? Any negative expoeriences doing this? Any positive from people with similar metrics?

The way to go?

D

 

[KL Mallender]

If you take a line pressure test you may find that the pressure peaks at the middle of travel with little or no increase from 3/4-full extension, which would indicate a weak "Line Bias" spring or operation, you should look for a linear increase of pressure from base idle(approx 80-100 psi) to WOT(approx 170-210) or better for extreme usage. You describe a "stock" trans pressure with blocked or stiffened accumulators as it is, when looking for "Headbanger" WOT shifts, I say becareful of what you wish.

Burnt clutches are the result of inadequate pressures applied to pistons/servos.

Proper(high) line pressures requred for clutch holding will never need to block/stiffen accumulation, in fact once you get the control pressures right you will most likely want to soften the accumulators to prevent "shocking" the transmission into pieces. Your Money, do as you wish, good luck.

Kevin.

 

[DorianL]

If you take a line pressure test you may find that the pressure peaks at the middle of travel with little or no increase from 3/4-full extension, which would indicate a weak "Line Bias" spring or operation, you should look for a linear increase of pressure from base idle(approx 80-100 psi) to WOT(approx 170-210)

This seems to exactly describe my problem... I need to track down that "line bias" spring.

My tire shredding 1 - 2 experience is what I used to have with my TH-350. Nonetheless, advice taken!


EDIT:
Spring 319?


D

 

[KL Mallender]

My AllData diagrams show it as #31, but there is pictures of the valve body floating around here someplace. It's the only one called "Line Bias", GM added its use in transmissions to bleed off control pressures after peak torque so as to not spill the coffee when shifts take place under WOT.

And anybody that has driven a th350 with it's accumulator blocked knows all about a "HeadBanger" shift and is living a charmed life if never blown the intermediate sprag afterwards at least once.

Kevin.

 

[SSedan64]

Some spring Info.>
Valve Body
Spring specs for BR2

 

[KL Mallender]

Thanks SSedan64, line bias is #319 in the first link.

Kevin.

 

[DorianL]

Back to plugging that hole...

Again - I have read with high TQ heavy cars with D5s it can work out quite well...

Anyone care to share any other thoughts?

 

[silvertoy]

I have done it many times,and it will help.what shift kit are u useing,i use CK now and do not need to plug the hole.with some shift kit you will get a clunking on the 2-1 down shift.

 

[DorianL]

PTS shift kit in there + billet servo and wide band properly clearanced.

Bruce is building me a pump. If my pressure is still not up, then I will go through the VB.

If that don't work, I am plugging that hole.

 

[bison]

Back to plugging that hole...

Again - I have read with high TQ heavy cars with D5s it can work out quite well...

Anyone care to share any other thoughts?

I never plugged the hole with a 12" converter. I do occasionally if the car has a looser converter. There should be no need to plug it with a D5. If the pressure rise is good then you shouldnt need to plug anything.

 

[matt69olds]

I drove a 87 442 on the power tour about 8 yrs ago. It had a mild 403 Olds and my first 200r4 that I personally rebiult. It had the stock converter, and I had blocked the feed holes to the accumulators. It was fun driving around town getting rubber on every 1/2 throttle upshift, but got VERY ANNOYING after about 2800 miles! First thing I did when I got home is ordered a different shift kit. The engine didnt have any power to brag about, I dont think the trans would have lasted long if it did! Good luck!

 

[DorianL]

Thanks people. At this point I think we can all agree that the reason my 1-2 is not "chirpy" is becaus the pressure is on the low side.

I'll start be replacing that pump with a high qulaity one. The we know we should be getting at least 250 to 300 PSI.

IF I don't see that kind of pressure, I am told that it is unlikely to be the case... so then I'll drop the VB and go through that.

Last resort will be plugging ore restricting that feed hole is I can't figure it out.

 

[quickt]

Line pressure is important. I would not block the accumulator let it do its job. good firm shift is all thats needed. 275psi + D5 + block 1-2 acc. = something is going to break and it could be you neck. ask any of us guys back in the late 80s early 90s who installed the Art Carr shift kit in our daily drivers.

 

[87GN_70GS]

Hopefully your intrmd shaft where it intersects the fwd drum has beefed up. Otherwise, all hard shifts will do beside make a neat sound is break that part right there.

 

[mikestertwo]

ask any of us guys back in the late 80s early 90s who installed the Art Carr shift kit in our daily drivers.

+1