There was alot of talk about this a while back. People saying they had to install a valve to make it happen.. A budy of mine who is very knowledgeable told me that my 88 Iroc L-98 should already have this feature and wanted me to try it. Well with the 2.77 gears needless to say I would need alot of room and risk a huge ticket
Well I am here to say that it does upshift into 4th gear at wide open throttle
I have a bone stock L-98 Iroc with about 60,000 miles now. I was installing some bolt ons and finished it up last night. I installed a cat back and a set of hooker headers with Y-pipe. I finished up about midnight and thought I would take it out for a spin to see how it sounded,,,since I live way out in the country and it was 12 AM the streets were empty and we have alot of straight roads out here. After driving around for a few minutes I remembered what my buddy said so I thought now is the perfect time. I ran the car out,,,,the stock shift points on my car are 5,000 rpms,,,,I was finally up in third and climbing,,,just as the needle touched 5,000 rpms it popped up into 4th (at 120 mph) at 125 I let off,,,took it home and parked it.
So whats the deal,,,,my trans has never been opened up,,,my buddy was right,,,so why are so many on here complaining about not having that feature,,,,just has me curious now. Is this a L-98 only feature? Larry.

TBI motors and other non performance cars had that feature I believe..... came with a gutless motor...

Are you saying the non performance cars also had this feature? I seem to remember so many people on here complaining about not having the feature,,,on which particular cars I am not sure,,but there was alot of complaining about it a few months back,,,with people buying a valve from B&M to install only to find out it wasn't doing what they wanted. Maybe my memory is fuzzy (old age) Maybe someone will chime in here that was part of that discussion a few months back. I just thought I would share my findings to let everyone know that a stock Iroc shifts into 4th at WOT, atleast mine does. "shrug" Larry.

My 1985 Trans Am with a TPI 350 will not shift to 4th at WOT. but my 1989 formula 350 will shift to 4th at WOT. the only difference between the two is the 89 also has the transmission cooler.

Well im here to say not all cars got the option, regarless of the package. I have a 1988 WS6 formula 350 with alminum DS, BW 3.27 rear and a upshift valve to 4th was not included on my car...does anyone know the parts needed to make this happen?

My Van would shift into OD @ WOT from GM. My GMC Jimmy would not.

I think the MAIN thing to remember is that some 700r4s will shift into OD @ WOT and some won't. If it won't the fix is relatively cheap and simple.

A Corvette/9C1/Van TV Sleeve and plunger installed in the valve body should give you WOT 3-4 shifts.

My Typhoon would upshift to 4th at WOT as well,,,but that had a very specific 700r4 from the factory with a unique valve body. That little blazer was not very stable at high speed either. Way too boxy and the wind would play tricks with you. I was just surprised to find that my Iroc would shift to 4th at WOT as well.
I had the part numbers at one time that added this feature to a 700 if it did not already. They are available through GM and also B&M makes the valve too. It's easy enough to find in their catalog or online. Larry.

i have an 88 iroc but it was rebuilt with a tci rebuild kit and it have a tci valvebody enhancement kit so now instead of 5000 rpm shift is a 6000-6400 shift last night i read what u guys were talkin about and wen i was comming home from the races there was a pritty big straight away now i anloy brought it up to about 6 and it didnt **** into o/d with how hight the shift kit is makein spool the engine do u think it will work if i manuly shift into o/d at wot???

20 bucks on ebay.

im just wondering if it was because i wasnt at the rpm that my shift kit permits the trans to shift????

Ive had my car to thetranny shop twice to get it to shift 4th but still a no go....i need a new tranny guy