Strange acceleration and shift.

B

Be2lose

In title only.
Something strange is happening since I added the 3.73’s. I’ve tried to narrow it down and have come up with this.

If I go WOT (passing) around 30- 40mph ( I think I’m in 3rd at this speed ) the car hardly accelerates although the rpm’s go to redline(from 1400 to 6300). Once it shifts into OD it takes off like a bat out of you know where.
I don’t know anything about automatics is this the torque converter not locking, clutch slipping or….?
I have:
3.73
Tac-lock
Chip, from Lonnie
 
Sounds like clutch plates or electrical problem. I don't know much but that's my 2 cents.

Are there any noises?
 
Be2lose said:
If I go WOT (passing) around 30- 40mph ( I think I’m in 3rd at this speed ) the car hardly accelerates although the rpm’s go to redline(from 1400 to 6300). Once it shifts into OD it takes off like a bat out of you know where.
Click to expand...

What speed is it "shifting to OD"???

If it's 85 +/- mph, you're shifting into 3rd from 2nd(with 3.73s).

If it's 130 +/- mph, you're shifting into OD. :eek:

Sounds like it could be a torque converter issue.
 
driller said:
What speed is it "shifting to OD"???

If it's 85 +/- mph, you're shifting into 3rd from 2nd(with 3.73s).

If it's 130 +/- mph, you're shifting into OD. :eek:

Sounds like it could be a torque converter issue.
Click to expand...

OK maybe I'm never getting to OD.

I'm confused. i'll check it again in the morning.

Just to be clear-I am saying that if I put my foot to the floor at around 30-40mph after it has shifted up to the higher gear it red lines and shifts gears before any real gain in speed. Not WOT from 0mph.

Could this be the fact that it is down shifting??
 
logres said:
Not with properly tuned shifts and 3.73 gearing.
Click to expand...

'scuse me?

my first gen, which was properly tuned.. from 30MPH would most definatley go into first gear.

Your speaking from experience, or are you just repeating what you've read on a message board?

Even with the stock tune, w/373's the car WILL downshift to first gear on a WOT run from 30MPH.

with stock gears it will drop to 1st gear at 37-38MPH and below
{depending on the speedo error).

Many times I did a 40 (indicated mph) WOT run and the car definatley goes to first gear with stock gears. BUT.. 40MPH (indicated) on my car with 245-50's was really 37-39MPH.
 
At 30mph it should drop down into first with 3.73 I'm with tommy on that one.
Car should only be at about 4k rpms or so.
 
maxmk8 said:
At 30mph it should drop down into first with 3.73 I'm with tommy on that one.
Car should only be at about 4k rpms or so.
Click to expand...

Depends on the tune I guess. Lonnie tuned my stage 3 tranny to only downshift to 1st when my speed is 25-30 mph. I've got 3.07 gears.
 
that is because with stock 307 gears at 40MPH the car will be IN 4th gear.

Lonnie knows that a 4-1 forced downshift is bad news in a 4r70w... so he "fixed you up" in the tune.

He didn't want you to do any 4-1 WOT shifts, which makes perfect sense from a tuning standpoint.
 
My shifts at normal acceleration

gear RPM/Speed(approx)
1-2 2200 @ 15mph
2-3 2200 @ 25mph
3-4 2000 @ 41mph / It downshifts @ around 32mph

So at 35mph (In OD) if I go to WOT it redlines before any real acceleration and downshifts to which gear? 1st?
If so why is it better at redline than right away?

also, before I do this I'm thinking it would be better to turn off the OD.
 
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Based on your original post, it sounds like your car is only downshifting to second (not 3rd) and because its not shifting all the way to first, the engine does not reach its power band because its so low in the RPM range, then when it shifts to 3rd, your MPH is closer to the RPM powerband range you should be at. If the car did shift to 1st, it would accelerate through the power range normally.

XLRVIII said:
Lonnie knows that a 4-1 forced downshift is bad news in a 4r70w... so he "fixed you up" in the tune.
Click to expand...

+1

driller said:
Absolutely! Before any "spirited" driving, click off OD!
Click to expand...

+2
 
XLRVIII said:
that is because with stock 307 gears at 40MPH the car will be IN 4th gear.

Lonnie knows that a 4-1 forced downshift is bad news in a 4r70w... so he "fixed you up" in the tune.

He didn't want you to do any 4-1 WOT shifts, which makes perfect sense from a tuning standpoint.
Click to expand...

I've got his stage 3 tranny...shouldn't be an issue. Just about the same tranny in that 10 second Mustang he's working with.
 
logres said:
I've got his stage 3 tranny...shouldn't be an issue. Just about the same tranny in that 10 second Mustang he's working with.
Click to expand...

IF it wasn't an issue, he wouldn't have spent time to "set up" your tune to PREVENT it.

Lonnie doesnt "do things" in his tunes.. "just to do them".
he wouldn't waste his time in such a manner.

Lonnie does things for very good reasons, knowledge being the KEY REASON.

guess you missed that "area" of Jerry's transmission thesis..huh wayne?
 
XLRVIII said:
IF it wasn't an issue, he wouldn't have spent time to "set up" your tune to PREVENT it.

Lonnie doesnt "do things" in his tunes.. "just to do them".
he wouldn't waste his time in such a manner.

Lonnie does things for very good reasons, knowledge being the KEY REASON.

guess you missed that "area" of Jerry's transmission thesis..huh wayne?
Click to expand...

No need to get nasty. I don't know enough about it one way or the other. I just figured a tranny that can handle 700 hp can also handle a 4-1 shift. I could be wrong. I don't see the need to publicly hound me over it.
 
(pot kettle much?)

Well I wasn't "hounding" you, in fact if you see "who replied to who" it would appear to be the other way around...

you always seem to "chime in" when I say something,so it really appears that you are hounding/trolling my posts

you were posting misinformed information, that is all I was trying to clear up...before someone came and and followed your bad information.

P.S. thanks for telling my my first gen wasn't properly tuned, again... who's hounding WHO?
 
The 4-1 downshift is bad for any transmission, even a race built one. The amount of fluid pressure required when "requesting" a 4-1 shift blows out the internal seals and causes an eternal fluid leak, which inturn causes a loss of pressure. This causes the trans to fail or not shift.

Imagine trying to clean a piece of bread with a high power pressure washer..... lol!
 
and it's even worse in the 4r70w..

cant remember "exactly verbatim" but it has something to do with the overdrive band not releasing quick enough and not having the pressure to release the clutch and it does something called "binding" (2 gears at once) and bad BAD stuff occurs.
 
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