montvaleplace

We have an 87 Grand National at the shop with a strange tranny problem. It came in with no second gear but running and driving ok otherwise, it would go from 1st to 3rd with no other symptoms. So we took the unit out and sent it to a very reputable shop nearby that we have used numerous times in the past with no problems. While it was out the owner decided he wanted a shift kit and 2500 stall converter. It felt good after us driving around town and it was really shifting hard leaving rubber in second easily. The owner livs about 15 miles from the shop and called me saying it was shuddering on the highway and then he heard something snap and had no gears either forward or reverse. We sent it back to the tranny shop, he found the shaft in the forward ckutch had snapped the front segment off. Probably about an inch broke off and the tranny guy said "thats from doing wholeshots". So he replaced it and found no other damage to the unit and gave it back. This time it drove fine for three days of us using it for errands around town and even drove on the highway for 20 miles or so. The day I'm bringing it to the owner a few towns over it started downshifting hard after I came off the highway and started what felt like ignition crossfiring at the higher end of 1st and at dip in during cruise in 2nd. Well needless to say I couldn't return the car and headed back to the shop but the same thing happened as the first time-it shifted from 1st to 2nd but when it went for 3rd I heard a snap and lost all gears including reverse. The tranny guy is due from vacation on monday and isn't going to like that it's back but the thing worked before the original overhaul it just had worn out 2nd gear. I know these trannys are sensitive to tv adjustment and this is how I dit it. Press the release tab and push it toward the firewall and release the tab, then press the throttle all the way open and it will click out as required.

Any experiences with this or fixes? I did hear of harder shafts and actually softening the shifts because they are sort of brutal but could hard shifts snap a shaft? and what is that shuddering and it feels like crossfiring?

Rickman48

So, how many 'holeshots' did you do??
Is your trans guy experenced with the 'hi-po' 200 from the GN?
EVERYTHING is different - bigger, more HD, and especially in the valve body!
Actually sounds like 2nd is still engaged when it downshifts to 1st - but I'm no expert!

Redog

I agree on the still in 2nd idea

Had a 93 cavy wagon like that. It's no GN, but it did the same thing, until I unplugged the solenoid

montvaleplace

I didn't do any wholeshots. The failure happened at about 3/4 throttle never having broken traction.

matt69olds

Quit messing around with the stock forward clutch housing and get a good aftermarket piece from CK Performance or another 2004R trans specialist. The stock housing is a well know weak point in the 2004R trans. Put a aftermarket housing in and you wont have that problem again

The GN 2004R trans is identical to the trans in Grandma Cadillac Brougham with the exception of the governor, valve body and 2nd gear servo. All the internal parts are the same from about 82 and up.

As for the TV cable adjustment, make sure the throttle body opens all the way. Push the adjustment button down and slide the cable back into the sleeve. Move the throttle to WOT from under the hood (don't use the gas pedal, flex in the throttle cable, throttle brackets,etc can effect adjustment) and the cable should ratchet out to the correct spot. Test drive, you can make MINOR adjustments in or out to adjust shift points. Find the minimum road speed that will allow a upshift into 4th gear, then mash the gas pedal to the floor. The trans should downshift back to first gear.

montvaleplace

I got the ck performance forward clutch drum with the billet shaft today and it will be going in asap. I'll post the results but from what I have been reading and others posting, it seems like we have the fix here.