: 700r4 question
Jun 9th, 07, 07:06 PM
The trans in my "new" vette has one weirdness...
It seems to work perfectly, shifts firm, never a delay going into gear, shifts at the correct rpm, even downshifts on dmeand as it should, but...
I don't seem to have any engine braking at all.
I can take my foot off the gas at 30 and pull it into first, and nothing. The motor just goes to idle. If I step on the gas, the r's come right up and it's definitely in first, take my foot off the gas... idle.
I don't recall this as normal.
Jun 9th, 07, 07:19 PM
Jim my 97 Tahoe is kinda like that... if I downshift manually approaching a stop light, it waits a long time before engaging the lower gear, wonder if thats some kind of safety feature?
Jun 9th, 07, 07:30 PM
yup gm got different strokes for different folks.at 30 mph you will never get first even in manual low.computer commanded lol.a shift kit will it or a computer reprogram.
Jun 9th, 07, 08:19 PM
This is a non computerized trans, except for converter lockup, which also works fine. I've had 2 of these before, a 91 and a 93, back wehen they were new, and I just don't remember this type of behaviour from them.
Still, I sure hope it's normal, or at least that the trans is not about to fall on the ground. I just bought this car last week, and plan to use it as my daily driver.
My truck, which is an 04 with a 4L60E, goes into first when I pull it into first... even at 45... the tach goes near redline, and she slows like she hit a wall.
Jun 10th, 07, 05:11 AM
the trans isnt supposed to do what you`re describing...the trans wont go into 1st if the speed is over the 1-2 shift point, per the governor...for instance, if your shift point is 43 mph for 1-2, than it absolutely wont go into first until you decel to 43...but if you`re doing 30, and pull the stick, you should go into first, and get motor breaking...also, if you`re going 43 with your foot off the gas, it wont pop right in, because of the tv system, but if you rap up the motor to the shiftpoint rpm, the trans will downshift, and stay in the selected gear...maybe there is a problem with the accumulator or something...jake or jag would know i`m sure...
Jun 10th, 07, 06:21 AM
For what it's worth...
I've only built a handful of trannys(and never a 700 yet) but my bro has been building them since I can't remember when. I asked him a question that is kinda the obverse of Jim's... in regard to why the Allison in my Duramax engine-brakes so hard in lower gears. He said he didn't do Allisons but it would about have to be due to the lack of using overrunning clutches.
So, if his theory is right, maybe your over-running clutches are doing what they are supposed to do and allow the back half to operate independent of the front half in a no torque situation........?
And something purely speculative because I could be a confused puppy. I have 2 700's and a few years ago did a tiny bit of researching before deciding I didn't want to bite off a 700 that I didn't have a home for yet
1. Isn't there 2 different vintages of 700?
2. Wasn't the overrunning clutch a weak point in the early?
Eager to see what a tranny guy says, cuz I think your tranny is ok Jim.
Jun 10th, 07, 07:31 AM
Hmmm. I don't know the answer...but sounds like you feel the need to "row" your automatic, so time to think about a tranny swap? ;)
Jun 10th, 07, 08:50 AM
A reply on the vette forum mentioned overrun clutches as well. Still waiting for more good info, here or there.
Biggest problem is the "crystal ball" I just bought the car a week ago... with a 30 day 50/50 warantee. If this will turn into a bigger problem, I need to bite the buttet and get it fixed. If it won't get bigger... then I'm not sure how much I care...
Jun 10th, 07, 09:04 AM
I got a dumb idea Jim, FWIW. Go test drive some more vette's with same setup/year model if you have time.
That's what I did on my Duramax. Made em let me drive about 4. All same, bought it.
Jun 10th, 07, 10:50 AM
What year transmission?
Has it had a valve body kit installed?
If it just doesn't have engine braking in low gear, there could be an issue with the low/reverse clutch pack, but if it works in reverse....
Some shift kits cause the over-run you are experiencing, but once you hit the gas and force the downshift, you should have engine braking.
Install a TransGo 700-R4 Reprogramming kit and it should fix it.
Jun 10th, 07, 08:07 PM
It doesn't have engine braking in any forward gear. It does in reverse.
Jun 10th, 07, 08:11 PM
The overrun frictions are probably the cause, a busted seal in the input drum more than likely.
It would have to come out to fix that, you should see a pressure drop when it is in 3rd gear compared to OD due to a leak if that is the case.
Jun 10th, 07, 08:28 PM
okay lets go back to first post you said new. it is new to you. what year is it?
Jun 10th, 07, 08:49 PM
It's a 93, with 70k on the clock.
Jun 10th, 07, 09:14 PM
ok thank you. than that clears it up a regular 700-r4 non comp car. if you downshift it and no engine break than it is a tranny problem. most likely than sprag lugs broke off. or forward clutch piston is cracked causing overun clutches to drag and burn.,if it a 50-50 thing ill charge you 1600 to do tranny installed. but you to far away.but listen dont take back to where you bought it. they probally got a tranny guy that will say cost 2500 and you pay half. you pay 1250 and they do it for 1600 they pay 350. they happy lool.90 percent of my work at this other shop i worked at did this i got to lie to people since they send me work.i quit there real quick i didnt want to go jail for fraud.
Jun 10th, 07, 11:13 PM
they happy lool.90 percent of my work i got to lie to people since they send me work.
And we wonder why most people think they are getting screwed when they go to the 'shop'
Jun 11th, 07, 08:07 AM
What a way to make a living. I guess I'm fortunate I can build transmissions for a living and not lie to people.
Jul 17th, 07, 10:27 PM
Bringing this one back up,
funny how that post got edited....