Big_Time_SS

iTrader: (1)

So here is the deal.
My brother just bought a 94 LT1 with a few mods.
Which are headers no cats, bbk tb, CAI, Flowmaster, and maybe a tune.
Transmission has a B&M ShiftPlus switch and maybe a shift kit. As far as I can tell it's the stock trans.
And 18" wheels with 275/40/18 tires.

It shifts into 1st and 2nd just fine, the only problem is at WOT the trans will not shift into 3rd, it hits the rev limiter until you ease of, then it will go in 3rd. If I try shifting it manualy, Same problem no 3rd.
At P.T. it shifts just fine no problems. What could be causing this problem?

Any help is appreciated.

performabuilt

iTrader: (25)

Well there are several possibilites not knowing the conditio or milage on the trans its a crap shoot to answer but possibilites are
1-worn 3-4 clucth pack , excessive clearance taking to much time to apply from comand to actual shift.
2-tuning assuming trans 3-4 clutch is good shift point set to close to rev limter or after rev limiter.

But basically the first thing is to determine if the shift is being comanded , I would get it on a scanner and watch the data stream for that first. However if the milage is high I would be on a failing 3-4 clutch set and that its time for a transmission.

LS1 SPEED

iTrader: (22)

I will add to the above statement by performabuilt... The B&M unit we have seen take a toll on a trans as with hand held programmers too. They increase line pressure electronically and from what I understand it will kill a trans.

correct me if I am wrong trans guru's

Big_Time_SS

iTrader: (1)

Thank you for the info.
The car has 128k mi. on it. So it is possible that its giving up. But it shows no problems before you get to the redline. It only becomes a problem when you go WOT. We will get it scanned and looked at by a pro. I just thought it maybe the shiftplus switch or the shift points. Thanks for your help.

performabuilt

iTrader: (25)

With 128000 on a performance car I will bet you are gonna need a trans, let us know if we can be of any help.

performabuilt

iTrader: (25)

Presure in excess can do damage to the trans I dont think changing it from tuning alone or with the B&M would not likley do damage at least in the short run. But now with a built trans with boost valves and the presure allready up its very possible the combo could.Thats why we have all our customers leave the line presure settings at stock levels,

Gilbert@Ace Racing

Indeed excessively high line pressure is detrimental to the unit. In addition, we have seen many transmissions fail due to improper tuning. I am convinced that the no 2/3 upshift at WOT is detrimental to the 3/4 clutches. I believe it is due to a partial apply at high RPM's. I could be wrong, but I have seen too many units fail a short time after experiencing that condition many times.

Now, that being said... The 1st place to start is to determine if indeed the shift is being commanded. If it is, then I would suggest that most likely there is excessive clearance in the 3/4 clutches.

You could try to make some adjustments to the shift parameters, but don't make coarse adjustments.

g

DRIVER456

Not to highjack this thread,But,What's the best way to tighten up the clearance on the 3-4 clutches.................Paul

performabuilt

iTrader: (25)

You can do it any of several ways. Using different thickness plates between the frictions is one way , If it alotta clearance you can even stack two steels ussually at the bottom of set, There are serveral different thickess plates available, Alternatley the top plates also come in several different thicknesses.

DRIVER456

Thanks Frank.................Paul