Nitrous transmission and tach issue

[JMo60]

well, i have this problem when i use nitrous on my 94 GP with 3400 swap, nitrous and a new GM reman transmission. When i engage my nitrous system, my tach seems to jump about 1000 rpm higher than i believe is accurate. the trans then refuses to shift at the normal shift point. the engine will bounce off the rev limiter between gears and take forever to shift, then slam into gear.
I am thinking a few things, first, the power source that i used to power my nitrous system interfears with the tach voltage, creating an inaccurate tach reading, and the computer shifts the transmission incorrectly because it believes that it is at a different rpm than it actually is.
the second possibility is that the transmission simply cant hold the extra power, and allows the clutches to slip too much, and im nuts in the head about the tach thing...

if anyone else uses nitrous on one of these cars, let me know what kind of things happen when you use your system.. .thank you much,

[PCGUY112887]

Did this just start to happen or has it been happening?

My bet is that the tranny can't hold it, especially if you are using the 4T60-E. Can you activate the nitrous system with an empty bottle and empty lines? That way you could sit at idle or something and activate it, see if your tach jumps around.

I am told if you use this modulator on the vac line for the tranny, you can adjust this modulator for more tranny pressure, hopefully holding the shifts. I have never bought it so beware the info may not be correct.

http://www.partsamerica.com/ProductDetail.aspx?mfrcode=PIO&mfrpartnumber=747017

[sharkey]

i highly doubt its a tranny issue. the 4t60e will hold a little bit of nitrous. if your tach is screwy, im guessing something is hooked up wrong or your grabbing power from seomwere you shouldnt. ive never heard of the tach jumping around or a tranny screw up when nitrous is porperly installed.

as said, turn the bottle off and drive the car with the system activated, see what it does.

[IsaacHayes]

Does sound like a trans issue. Mine has done that on a 4-1 downshift before, revving up, then bouncing off the limiter then slamming into gear.

3400_modified might know more. He knows the 4t60e pretty well and has nitrous.

[PCGUY112887]

4-1 downshift? You sure about that? :P

[sil]

lol, i do it lots, OD to first, it likes to drop to first, and of course it hits the limiter and shifts to next gear

do your guys' 4t60-e's seem to take its sweet time downshifting ?

[Darin]

Are you saying that when your injecting nitrous in to your engine the RPMs increase? Nitrous will raise your RPMs alot.

And if your hitting the rev limiter while spraying the nitrous into the engine, Your lucky the engine still runs.

To me it sounds like you need to adjust your shift points to a lower RPM. (shift sooner) Or raise your rev limiter to a higher RPM (not really a good idea on a stock engine)

[JMo60]

well, im gonnna try to move my power supply. with empty bottle and no fuel line attached it still does it.
I have had nitrous on 2 different transmissions now, both did it, the old one burned clutches ( high miles, abuse) the new one has less than 3000 miles on it.
i tried deactivating the nitrous as a i approached shift point, but when i cut the nitrous, the tach dropped nearly 1000 rpm, and i had to motor it out till shift.(loosing lots of time)
The engine is fine running over 6k rpm, i have ls1 valve springs.. any other ideas are appreciated

[blackbombshell95]

I have the transmission problem too. When i'm using a 75 shot and I let it off while I shift the trans gets stuck in gear and then shifts a second later.
Which is why i'm getting a perf trans built right now.

Also i'm using a direct 16gauge wire from the battery as my power supply for my nitrous switch/management unit. Just make sure your nitrous isn't engaged while you bounce off the rev limiter.

[IsaacHayes]

PCGUY, it sure seems like that. At ~ 35mph, in OD, flooring it, it would go right to first like instantly and just fly. Then it would sometimes get stuck in neutral and mess up. Now I drive in town in D only, and when you punch it you feel it go into 2nd, then into 1st. Never messes up when it does that. I put in the GM seal conditioner for a different problem (which it fixed) and it shifts a lot faster now, but I haven't tried the OD-first shift now.

[JMo60]

blackbombshell, just curious, do you know what kind of 1/4 mile times your car puts down on the bottle?

[blackbombshell95]

Yes. 15.004 with a 75hp shot. And a 15.4 with a 55 shot.

Mods are short ram intake, FFP mounts/pulley, plugs/wires, 2.5" crush bend exhaust w/ high flow cat. I dyno'd 134 whp with no nitrous. This is on a 95 3100 turd engine.

My car is very heavy and had no weight reduction on street tires. I was pulling 2.3 60 ft times on all my runs. My hood weights a lot. Plus i'm a 220lb guy.

My personal best N/A was a 16.2. But that day I ran a 16.4 best n/a.

[3400-95-Modified]

My car did a 13.818 on a 100 shot with a 4t60e, 3.33 gearing 2060 stall converter and EP LSD. it was also a 3400 on a OBD1.5 ECM.

I now have a Hybrid with headers, Milzy stage 1 cam, head work, all on a OBDII system, and the same trans with a rebuilt LSD.

I'm expecting quicker than that this year.

And no my 4tsleezy doesnt take its sweet old time downshifting... Its nice quick and crisp.

oh yeah it did a 14.5 on a 75 shot a LONG time ago, with the stock 2.93 trans and 1650 converter

[JMo60]

when i had a 3100 and a 75 shooter, i went 14.30, so far with the 3400 i have only managed a 14.00. if the thing would shift right, i see no problems with a 13.80... on all motor it has gone 15.60s on a good day usually in the 80s though

3400-95-modified, have you had any transmission issues while using nitrous? i know that we have a very similar setup, just curious. thank you

[3400-95-Modified]

I havent had any issues... Mine was always good. Only time I had a problem is when I went to the 2095 converter, I started to hit the limiter on the 1-2 shift. Now with DHP I can easily avoid that one.