I have a 1938 Oldsmobile business coupe it weighs around 3050 lbs with me in it it has a stock lq4 out of a 06 Chevy express with a 4l60e with up grades and I was told by the tourk converter shop with my motor and weight of the coupe the stall would be around 2200 to 2900 but I’m not sure it’s a gm310-Vj tourk converter the stall is 1800-2000 with the v6.
it also has the stock 04 truck harness dbw and psi conversions did my computer deleting vats and extra stuff not needed
and I asked and they turned off the neutral safety switch.

i also have a b&m quick silver shifter in it .

i noticed today if I leave it in drive it will burn off the tires tell it shifts to second and if I put in 1st it won’t stay n first the rpms get to a certain rpm and it shifts into second with out me shifting and doesn’t burn out it seems dogish.


Any ideas why ?

thank you kelly

 

It does this because it's supposed to. It's a safety shift function.
The stock tuning will force a shift into 2nd gear even if you are in D1 on the shifter.
The best way to correct this is to use a valve from the transgo HD2 kit. The 1-2 shift valve.
You can also try a tune to correct the issue.

 

Ok thank you I figured it was I’m used to the older ones where you can manually shift it if you want.

 

Then you're not used to stock older transmissions.

TH400 and th350 both had the same safety shift function in stock form. Neither would let you downshift to 1st if you were moving to fast...and both would upshift out of first if the wheelspeed/rpm was too great.

 

What stock automatic transmission were you referring to? I am curious...

Like Maroony said older stock GM automatic transmission usually required valve-body modification... For example the THM400 usually will not hold first gear, it will do the same as you are experiencing and shift up into second gear on its own.
Also like MaroonMonsterLS1 said... This is a safety feature... Think of it as away to try and keep from over revving an engine that does not possess a rev limiter.

"Shift Kits", "Shift Reprograming Kits", and any other "TRADE MARKED" name products that have been around for more than half a century to modify auto-trans. valve-bodies make it possible to hold any gear range to any RPM (Without a Rev Limiter).

The TransGo 1-2 shift valve modifications as already posted is my recommendation.
Otherwise Talk to Dana (PBA on our forum) at ProBuiltAutomatics to set up completely anything you could need for the 4L60E units.

 

My turbo 350 held first it must of had a shift kit then it would not shift if I had it In first tell I shifted into second if it was in drive then yes it would shift through all the gears normally