904 trans banging full throttle 1-2 upshift??

Posted By: tpabayflyer

904 trans banging full throttle 1-2 upshift?? - 10/15/08 04:27 PM

I actually have an A-999 lockup trans freshly rebuilt. It has the low first gear and new alto clutches. I have had the pan off twice in 300miles and both times noticed black sediment in the bottom of the pan??? Trans fluid looks great (synthetic) with no burning smell. Trans pan is stock.
I did have a problem with slippage and tightened up the low gear band and it hits nice and hard now. While I had the pan off I also tightened up the other band to spec.........

I did install a transgo shift kit per instructions and have no slippage but the 1-2 shift gets weird at full throttle only. At 6,000rpm it made a couple of bangs and the trans was momentarily dis-engaging?? 2-3 shift is fine and since I changed the pan gasket yesterday it seems to not be as bad but it still is not right. Fluid level shows about 1/2 quart on the high side and I am using a nice plate style trans cooler..... Anybody know what this is?? TIA TBF

Posted By: Dragula

Re: 904 trans banging full throttle 1-2 upshift?? - 10/15/08 05:20 PM

If you don't put a deep pan and sump on it, you will starve high gear.....Trust me. You must put a deep pan out of it, because it sucks up all the fluid under hard accel, and there's nothting left for the 2nd to 3rd shift...You will kill high gear without it.

Posted By: Anonymous

Re: 904 trans banging full throttle 1-2 upshift?? - 10/15/08 05:54 PM

I don,t know exactly what you mean by disengages,is it like it goes to neutral or feels like it drags. If it drags, back the front band screw out a little.

Posted By: JohnRR

Re: 904 trans banging full throttle 1-2 upshift?? - 10/15/08 06:54 PM

did you take out the accumlator spring and block the piston ?

also disengaging in 2nd ?

rpm jumping up like a downshift ? front band is slipping

or rpm jumping like its in neutral ? rear clutch is slipping/disengaging

Posted By: tpabayflyer

Re: 904 trans banging full throttle 1-2 upshift?? - 10/15/08 07:05 PM

It is not disengaging completely or dragging at all.... It seems like it disengages for a split second and when it does, it makes a huge bang under the car which may be due to shocking the driveline. I do have brand new u joints.....
This only happens on the 1-2 shift... 2-3 is fine...

FWIW I did tighten the band in the trans (high gear?) as it was set up a bit loose, I tightened it to 2 1/2 turns out from snug and it seems that maybe it helped a bit but the 1-2 shift is rough.. not a clean bang/chirp upshift but more like a split second roughness during the 1-2 upshift.... TBF

Posted By: tpabayflyer

Re: 904 trans banging full throttle 1-2 upshift?? - 10/15/08 07:06 PM

Am I running the pan dry maybe??? I am shifting at 6,200rpm.... TBF

Posted By: JohnRR

Re: 904 trans banging full throttle 1-2 upshift?? - 10/15/08 08:25 PM

what do you have for a pan on it ?

As far as the 1-2 , it might be slipping a bit before it grabs firmly , what ratio apply lever did you use ?

Posted By: Dragula

Re: 904 trans banging full throttle 1-2 upshift?? - 10/15/08 08:27 PM

Quote:

what do you have for a pan on it ?

As far as the 1-2 , it might be slipping a bit before it grabs firmly , what ratio apply lever did you use ?

http://store.summitracing.com/partdetail.asp?part=tci-127900

Posted By: tpabayflyer

Re: 904 trans banging full throttle 1-2 upshift?? - 10/16/08 12:11 AM

I am using the stock pan and a 5.0 lever..... fwiw the 2-3 shift is fine thanks TBF

Posted By: dusturbd340W5

Re: 904 trans banging full throttle 1-2 upshift?? - 10/16/08 12:50 AM

my experiance is 5.0 don't work too well in a 904 I would use a 3.8 or 4.2

Posted By: Evil Spirit

Re: 904 trans banging full throttle 1-2 upshift?? - 10/16/08 12:52 AM

1-2 shift is accomplished by the low-reverse band releasing (if applied) and the front (also called 2nd gear or kickdown band) being applied by the servo and over-running the rear roller clutch. It doesn't sound like the band is applying fast enough to cleanly clear the rear roller. I usually set my front band to 72 in.lbs., then back off 2 turns. I don't know what you had it set at before, but I think you mentioned that it got better when you reduced it to 2 1/2 turns.

Posted By: Evil Spirit

Re: 904 trans banging full throttle 1-2 upshift?? - 10/18/08 05:29 AM

Posted By: CJK440

Re: 904 trans banging full throttle 1-2 upshift?? - 10/18/08 01:12 PM

Hardly an expert but know enough to be dangerous.

If his VB has low band apply and there is black sediment is there too much overlap in 1-2??? If thats the case the 5.0 lever would apply slower and limit the apply.

Could the low-rev band been too tight??

Posted By: kenworth_goose

Re: 904 trans banging full throttle 1-2 upshift?? - 10/18/08 01:35 PM

Do you have the kickdown properly adjusted? If not it will eat the front band out of it. I had a 360, 904 in a dakota a few years ago and learned the hard way. After rebuilding it 3 times because of the front band I learned. I'd say the material you are finding and the flash you are talking about in the 1-2 shift is the front band. You will likely need a new band and front drum as well.

Posted By: John_Kunkel

Re: 904 trans banging full throttle 1-2 upshift?? - 10/18/08 07:45 PM

If the "momentarily dis-engaging" happens on a manual 1-2 upshift it's probably a case of severe overlap; on a manual upshift the rear band is slow to disengage and the trans is momentarily "in two gears" at once.

Posted By: 70Challengerse

Re: 904 trans banging full throttle 1-2 upshift?? - 10/18/08 07:53 PM

Quote:

If the "momentarily dis-engaging" happens on a manual 1-2 upshift it's probably a case of severe overlap; on a manual upshift the rear band is slow to disengage and the trans is momentarily "in two gears" at once. [/quoteExactly was I was thinking,I have in the past used a spring from a t-35 trans and install it in the rear band...works great and no over lap.

Posted By: JohnRR

Re: 904 trans banging full throttle 1-2 upshift?? - 10/19/08 02:50 PM

Quote:

Hardly an expert but know enough to be dangerous.

If his VB has low band apply and there is black sediment is there too much overlap in 1-2??? If thats the case the 5.0 lever would apply slower and limit the apply.

Could the low-rev band been too tight??

the 5.0 applys a little faster and has more leverage to hold the drum , but it releases slower .

Posted By: tpabayflyer

Re: 904 trans banging full throttle 1-2 upshift?? - 10/20/08 04:51 AM

Well, today while driving the car the trans finally let go... 1-2 shift let out a nice big bang and that was all she wrote.... no forward gears or reverse..... but PARK still works

O.K. now what... do I look for a small block 727 to build or do I try and fix this 904 (999)???????
I do like having the 2.74 low gear but maybe I should just settle for the 727 and get a higher stqall converter??? TBF

Posted By: goldmember

Re: 904 trans banging full throttle 1-2 upshift?? - 10/20/08 05:01 AM

Let me know if the tranny needs a new home,sorry I just sold a SB 727 or I'd offer it in trade.

Posted By: JohnRR

Re: 904 trans banging full throttle 1-2 upshift?? - 10/20/08 12:28 PM

Quote:

Well, today while driving the car the trans finally let go... 1-2 shift let out a nice big bang and that was all she wrote.... no forward gears or reverse..... but PARK still works

O.K. now what... do I look for a small block 727 to build or do I try and fix this 904 (999)???????
I do like having the 2.74 low gear but maybe I should just settle for the 727 and get a higher stqall converter??? TBF

No forward tells me something inside the trans broke ( obviously ) , but no reverse ? it's either a broken input shaft , the splines on the front of the output shaft or the pump , drop the pan and see whats in there ...

Posted By: JohnRR

Re: 904 trans banging full throttle 1-2 upshift?? - 10/20/08 12:30 PM

Quote:

Quote:

If the "momentarily dis-engaging" happens on a manual 1-2 upshift it's probably a case of severe overlap; on a manual upshift the rear band is slow to disengage and the trans is momentarily "in two gears" at once.

Exactly was I was thinking,I have in the past used a spring from a t-35 trans and install it in the rear band...works great and no over lap.

T-35 ???