meadmarc

So I bought a 3.42 rear off a v6 Firebird, replaced all the bearings and seals, and apparently did not set it up quite right because it whined right away.

Flat bedded the car to a local transmission shop. The guy, who has a reputation for being very honest and fair, told me the gears were messed up, he could adjust properly but it would be noisy. No money for new gears right now, go for it.

But as I was leaving, he commented about how my shifting would be off with the new gears. I was confused- I thought the only issue as far as the transmission was concerned was the spedometer would be off.

But the car is shifting horribly; RPMs go almost to redline before shifting, and OD appears to be completely gone.

I did loose some fluid when I removed the driveshaft to install new Ujoints, but I made absolutely sure all lost fluid was replaced.

I also yanked on the TV cable to see if it had froze up or something, but it was fine.

What happened?

ninetyone

iTrader: (2)

trans shifting has zero to do with gears. Sounds like your tv cable needs adjusting. Set it to stock.

meadmarc

Good, that's what I was thinking as well about the gear ration, thought I was loosing it.

So I know where the TV cable shows up at the TBI, but where does it end and how do I set it to stock?

Thanks in advance!

Zach/90\irocZ

iTrader: (6)

i agree .. freeway rpm will change depending on gearing .. hence stock car had 2.73 for better mpg

TV Adjustment is critical and can ruin a trans in a heart beat maybe not that quick but over time yes.. and damage might already have been done depending on how long you been driving like that .. and its isnt out the norm when performing upgrades that other gremlins will come up not relted to upgrade .has happen to me
TV Adjustment
The cable must be adjusted so it is pulled fully out at wide-open throttle. To make sure disconnect the cable, hold the throttle wide open with your left hand, pull the cable fully out with your right hand and see if the cable end lines up with the button on the throttle lever. The cable should also be pulled out 3/8 to 1/2 of an inch at idle.

but gearing and shift points dont go hand and hand the issue is the transmission and it is about to go out

overdrive issue try this
A stuck valve, trash in the fluid or an air pocket, usually causes this. Raise the rear wheels off the ground, place the transmission in overdrive position. Run the speedometer as high as 100 miles per hour, pop the throttle on and off and see if you can force a 3-4 shift. Once it makes the first 3-4 shift, work the shift lever back and forth between drive and overdrive until the 3-4 shift works correctly.

high rpm shifting try
If your transmission doesn’t shift out of first gear or shifts hard at too high a R.P.M. this doesn’t always mean you have a problem. This could be a stuck throttle valve caused by a small piece of trash. This sometimes happens after a rebuild. Sometimes the throttle valve can be unstuck without removing the valve body. Get up to about 20 to 30 M.P.H. and hit the gas pedal on and off hard with your foot. This might do the job. If that doesn’t work remove the throttle valve cable end from the throttle, with the motor at idle in park, pull the cable in and out very fast, this might work, if not the valve body must be removed by a transmission shop to be unstuck

trying changing fluid and filter also theres a possiblity of needing rebuild to keep in mind

shift points are change by putting in light or heaver springs in
TV Cable Contrls pressure

as to what exactly happend who knows its hard to tell until you open up the trans just the nature of the beast you can loose alot of fuild from trans tail depending on angle of car and that could of loosen some debri in the trans and you putting new fluid thats my best thought

big gear head

Changing gears also changes the RPMs of the transmission governor and will change the shift points if you don't recalibrate the governor. There are spring and weight kits for the governor that you can use to get it back to where it needs to be. This is related to speed and not engine RPMs.

meadmarc

Not sure how I missed all that, I thought you could just bolt in the new rear end and change the speedometer gear and you were good...

Zach/90\irocZ

iTrader: (6)

i agree with you
my math could be off but you get the idea
speed difference between 2.73 and 3.42 assuming stock rear tire height
3.42 - 65 mph = around 2050 rpm
2.73 - 65 mph = around 1631 rpm

A 419 Rpm increase
and i believe there about a 10 to 14 mph difference from 2.73 to 3.42 that i dont remember i could be wrong
i also cant remember where my WOT Shifts where at
heres a refrence there not exact as every setup is different but gives you a idea

WOT Shifts with tock pieces and not playing around with the springs and weights etc etc

• Corvette Governer 5900 to 6500 rpm
• v6 Governer 5600 to 5900 rpm
• v8 Governer 4100 to 4700 rpm

project89

iTrader: (1)

going from 2:73 to 3:42's will be a 690 rpm increase
2:73 to 3:73 is a 1,000 rpm difference
2:73 to 4:10 is a 1,370 rpm difference

tires make no difference unless tire size is changed at the time of the gear change

Zach/90\irocZ

iTrader: (6)

What equation did you use ? seems kinda high looks like your confusing 3.73 with the 3.42 as there would be around 690 rpm difference going 2.73 too 3.73
1000 rpm difference from 2.73 to 3.73 just seems out there
but i could be wrong as i dont know everything and learn new things everyday

what tire height and overdrive ratio ?
i used 25.5" for tire height and overdrive at .70

and tire height does make a difference if its taller or shorter than stock and i assumed stock as he didnt stated what rear tires and wheels that he is running

project89

iTrader: (1)

what gear the transmission is in makes no difference if u want to know the rpm increase for any gear change just subtract the smaller number from the larger i.e say u have 2:73s and want to switch to a 3:73 u subtract the 2:73 from 3.73
u get 1.0

say u go from 2:73 to 3:42's and want to know the difference in rpm subtract 2:73 from 3.42
this = .69
so u add a 0 to the end at its 690 rpm

anything before the decimal is 1k rpms and anything after the decimal u add a 0 to get how many hundred rpm

say u go from 2:73 to 3:73 and u cruise at 55 mph in 3rd gear @ 2,300 rpms
with the 3:73 gear u would cruise 3,300 rpm @ 55 in third gear

the gear ratio number is basically how many turns of the driveshaft it takes to get one full rotation of the tires

2:73 takes 2 full + 3/4 rotation to rotate the tires one full turn
3:23 takes 3 full turns + almost 1/4 rotation to turn the tires one full rotation
etc etc

Zach/90\irocZ

iTrader: (6)

hmm intresting you are correct but

(Axle Ratio x Vehicle Speed x Transmission Ratio x 336.13) / Tire Diameter

thats the equation i used

but i get that i just think thats a inaccurate way of calculating rpm when driving on the road as you want your rpm at you desired range my reason is that there is drivetrain slippage which equates to engine and driveshaft rpm differences

meadmarc

Seriously great discussion- but, wondering how I can solve my sifting problem.

If I put the 2.73 back on, that will obviously solve the whining problem, but how likely is that to correct the irregular transmission behavior?

project89

iTrader: (1)

u need to buy a governer calibration kit

Zach/90\irocZ

iTrader: (6)

i agree

but if you having a whining issue thats totally different issue

meadmarc

Started car. While running, pulled the TB cable about 100 times. Drove around the block. It shifted normally 1,2,3 but not OD. Came home, parked in driveway. Left car running while I cleaned the garage for an hour. Jumped back in car, drove around the block. I now have all gears, things work just fine.

Quit my job, opening a transmission shop tomorrow.

ninetyone

iTrader: (2)

changing gear ratio will not change anything in the transmission,but may throw off the speedometer. Your mechanic may have messed with your tv cable or by coincidence ,you may have had some trash or debris in your transmission causing your tv cable to get stuck. One thing for sure is I would not try and manually shift that tranmission. Just leave it in drive at all times.