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| 904 issues https://slantsix.org/forum/viewtopic.php?t=45755 |
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| Author: | Volare4life [ Thu Jul 28, 2011 5:21 pm ] |
| Post subject: | 904 issues |
well the trans ran great prior to and for awhile this modding, heres the run down i modified my valve body in the '76 904 per transgo's TF-2 kits instructions, including tightening the clutch bands. now heres my problem, the shifts are amazing, but now when you step on it from low rpm's you can feel a thunk, and i can't tell if its the torque converter or bands...... also under low rpm's driving the car surges ever so slightly, like the clutchs are slipping, but under higher rpm 2200+ its fine no slip but does feel like its lost power. the instructions stat to tighten the front band till its snug, then backing off 2 turns and tighten jam nut. and the rear band (single wrap) tighten snug then back off 2 1/2 turns. what do you guys think ?? is it possible to re tighten the bands to fix the slipping ?? -Mike |
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| Author: | bigslant6fan [ Fri Jul 29, 2011 8:43 am ] |
| Post subject: | . |
What gears does it slip in? Is your shift and kick-down linkage adjusted properly? (VERY important!) The TF-2 should chirp the tires in all gears at WOT. If you reduce the kick-down linkage adjustment to lessen the shift,it will slip at light throttle. That 2 1/2 turns on the rear band sounds too tight,but I'll have to check my service manuals,and ask you a few more questions first. |
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| Author: | Volare4life [ Fri Jul 29, 2011 10:07 am ] |
| Post subject: | |
slips in 2nd and 3rd, shift linkage is run from the hurst v-matic 2, i'll double check but at WOT the kick down is full rear, but when it shifts for some reason the engine bogs down then picks right back up. -Mike |
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| Author: | bigslant6fan [ Fri Jul 29, 2011 11:21 am ] |
| Post subject: | . |
Just a guess,but maybe the valve body is loosening,causing a leak,2nd and 3rd gear passages are next to each other.Have you used this shifter on this trans before installing the shift kit? Most trans guys (including me) H-A-T-E aftermarket shifters. One shifter doesn't work perfectly with every make and model of trans under the sun. They often work OK with GM trans ,but don't have the shift point locations correct for a mopar trans.This can cause it to be partaily in two gears at once.One warning sign would be trouble shifting into either park or manual LOW. |
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| Author: | Volare4life [ Fri Jul 29, 2011 12:34 pm ] |
| Post subject: | |
i'll have to check the valve body, but yes i used the shifter before the TF-2 kit no issues, maybe i messed up somewhere in the VB itself, i realllllllly don't want to drop the pan, my motto is " if the pan comes off, fresh fluid goes in" and at $4.17/qt for atf+4 it gets expensive quick, that and i just lost all the foward gears in my 2000 auto neon fml, thats 4.5qts right there lol -Mike |
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| Author: | slantzilla [ Sat Jul 30, 2011 2:26 am ] |
| Post subject: | |
If it's bogging the motor on the shifts it really sounds like you have shift overlap. (trans is in 2 gears at once) Slipping in 3rd gear will not be a band adjustment, no bands are applied then. Slipping at low RPM sounds like a pressure issue, like maybe a leak in the VB. 
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| Author: | wjajr [ Sat Jul 30, 2011 4:53 am ] |
| Post subject: | |
Valve body bolts may not be torqued properly. If VB isn’t fully seated, and at torque specks, it will leak internally. If it is torqued too tightly it can deform causing problems as well. |
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| Author: | Volare4life [ Sun Jul 31, 2011 5:30 pm ] |
| Post subject: | |
well the slant aspen in the boneyard didn't have a tranny, I can pull the VB out of newer 904 cars with SB's right ?? -Mike |
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| Author: | bigslant6fan [ Mon Aug 01, 2011 11:45 am ] |
| Post subject: | . |
Assuming your trans is still a '76 S/6 trans,you can't use a VB for a '78-up lock-up trans. Also 70-up V-8 904s and 75-76ish S/6 904s had an additional Hyd. circuit in the VB that I don't believe will work with earlier main cases. I'd obtain a 200 and 400 PSI test gauges and do pressure tests as explianed in the service manual. Since you've installed the shift kit, expect line and reverse pressure to be about 50 PSI higher than stock specs. I don't recomend atf+4 in older high mileage transmissions. At the very least,obtain an inch-pound torque wrench and check the VB bolts |
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| Author: | icepaddles [ Tue Aug 02, 2011 2:51 pm ] |
| Post subject: | |
You mentioned a clunk, The overrunning clutch could be slipping just slightly before the roller bearings engage and stop the stator from rotating, if you are on a floating pull/coast situation (cruising) the same could be true. If you've ever rotated the inner race of a one way clutch (overrunning clutch) it will squeak slightly and I think if you had the right coefficient of friction the lockup may be delayed, are you running some friction modifier or moly additive in it? I think the O/R clutch in the torque converter would be more suseptable to that. |
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| Author: | icepaddles [ Tue Aug 02, 2011 5:30 pm ] |
| Post subject: | |
If the stator were rotating, you lose that gear reduction hence it would bog the engine. Loosening of a rear axle pinion nut might get you there too, a surge at cruising, a clunk, power robbing. |
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| Author: | icepaddles [ Tue Aug 02, 2011 6:04 pm ] |
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you could road test by; 1.place gear selector in 1st, rev out so you know itll shift. 2. simultaniously release gas peddle and place selector in 2nd, then mash the throttle. 3. repeat for 2-3 shift. Youll know if its shifting and youll know if its slipping afterwards. |
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| Author: | Volare4life [ Thu Aug 04, 2011 4:38 pm ] |
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no friction modifier, don't really understand your testing method, -Mike |
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| Author: | icepaddles [ Thu Aug 04, 2011 6:58 pm ] |
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Test would raise pressures enough to cause a hard shift (get enough speed so it wont down shift again, or dont push throttle far enough), if you let off at the same time it should shift quickly which would seperate the shift point from the equation. If it bogs after the quick shift, some thing is misaligned or a sprag clutch is slipping. I just went through a 518 in our work truck that had the rear bearing come out in 20pcs without a clue exept for a whine that decreased with leaving it out of overdrive, no fluid junk or grinding, I took it out cause the inner rear clutch seal shrunk which is common with those, no forward. |
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| Author: | icepaddles [ Fri Aug 05, 2011 8:36 am ] |
| Post subject: | |
Think finess, the idea is to seperate each element in the test proceedure. |
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