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727 question for experts
#1239378
05/25/12 06:55 AM
05/25/12 06:55 AM
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Ck[FIN]
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Hi
I have had a small problem with my trans. I have slight 2-3 overlap and it burns 2-3 clutches in front drum in about 20-30 passes. It also kills the front band in long term use. Luckily carbon fiber band takes lots of abuse.
It has old cheetah transbrake VB. Early style front servo with stiff dual springs. Front drum has 6 clutches and 15 stiff return springs.
Kd-lever is 4.2. Best result so far was to make lots of clearance in clutch pack, about 0.125". Orifice plug cannot be used because of the transbrake.
Any good ideas? Better VB, maybe A&A/Griner/CRT??
Last edited by Ck[FIN]; 05/25/12 06:56 AM.
-1965 Valiant 9.03s 358cu.in R5P7-
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Re: 727 question for experts
[Re: Ck[FIN]]
#1239379
05/25/12 07:59 AM
05/25/12 07:59 AM
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Frostbitefalls MN (Rocky&Bullw...
gregsdart
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What are you using as a band adjustment? 2 1/4 turns? You can go more to slow it down and decrease overlap. Just as long as you have enough travel to fully engage the band.
8.582, 160.18 mph best, 2905 lbs 549, indy 572-13, alky
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Re: 727 question for experts
[Re: gregsdart]
#1239380
05/25/12 09:37 AM
05/25/12 09:37 AM
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Ck[FIN]
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I was using 2 turns. I could try a little more, it shouldnt affect too much on the 1-2 shift.
-1965 Valiant 9.03s 358cu.in R5P7-
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Re: 727 question for experts
[Re: Hutch]
#1239384
05/26/12 12:24 PM
05/26/12 12:24 PM
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Ck[FIN]
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Quote:
Depending on how fast the car is , you can likely take away some direct clutch's. Make sure you have a bleed hole drilled in the drum also.
Hutch
I drilled 0.05" hole to drum and it the 2-3overlap is gone but it slips the clutches and burn them in just 10 passes. Smaller hole maybe?
Last edited by Ck[FIN]; 05/26/12 12:25 PM.
-1965 Valiant 9.03s 358cu.in R5P7-
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Re: 727 question for experts
[Re: Ck[FIN]]
#1239387
05/26/12 01:41 PM
05/26/12 01:41 PM
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440Jim
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Quote:
Front drum has 6 clutches and 15 stiff return springs.
Kd-lever is 4.2. Best result so far was to make lots of clearance in clutch pack, about 0.125".
I am not sure why your setup is having overlap issues shifting 2-3. The orifice is the typical method to try once you have all 15 front clutch springs in it and either the 3.8 or 4.2 lever. I don't know about the transbrake effect.
I agree a small bleed hole of 0.050" (1.25mm) in the front clutch area (either the drum or the piston) should not be a problem. Check the front piston seal.
You are thinking right on the front clutch clearance. Too tight can put small burn marks around the clutches. From what I have seen, 0.015" per clutch is good (6 x 0.015 = 0.090") so you have enough. Minor burning can be lack of lube, major burning is an apply issue (poor sealing, etc).
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Re: 727 question for experts
[Re: 440Jim]
#1239389
05/27/12 04:53 AM
05/27/12 04:53 AM
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Thanks for the tips, i`ll check the piston and drum seals first, then drill some bigger cooling holes. Then check the line pressure (forgot to check it) and give it a go.
-1965 Valiant 9.03s 358cu.in R5P7-
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Re: 727 question for experts
[Re: Ck[FIN]]
#1239390
05/27/12 10:03 AM
05/27/12 10:03 AM
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440Jim
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For what its worth (FWIW), I run my Griner valve body at 165 psi (turned it down from 180) with 5 front clutches (aluminum drum). These clutches have over 700 passes and when I inspected them at 600 they were still in great shape.
511 CID, 9.30s at 3225 lbs, 1.2x sixty foot times, foot brake
I estimate 750 hp and lots of torque. 4.10 gear, 31.8" tall slicks
If you make a restrictor plug from a set screw (1/8 NPT) and tap that hole in the case, then you can easily change the restrictor hole size or even remove it. Just drop the valve body. So you can see if it solves the 2-3 overlap issue and if it effects the transbrake.
EDIT: I had another thought related to checking or replacing the front clutch piston seal. It could be losing fluid/pressure at the rings leading to the front clutch. Look at both the condition of the rings, the ring grooves, and the surface they seal against. While you are at it, check the rings on the front servo too.
Last edited by 440Jim; 05/27/12 12:57 PM.
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Re: 727 question for experts
[Re: 440Jim]
#1239391
05/27/12 03:58 PM
05/27/12 03:58 PM
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I have aluminium drum with steel liner and billet piston. I use the piston seal that came with the drum so it should be correct. It has bronze bushing and teflon rings, they are in perfect condition. No signs of wear. Front servo was checked 1month/6 passes ago and it had good rings. The overlap wasnt noticeable when driving WOT at 9200+ rpm, but it was there. Now with the bleed hole its gone(no burning marks in front drum surface anymore). i will check the line pressure, it could be too low, i bough the vb from a guy that drives super stock so it could be anything. I wonder why he sold it so cheap  It`s still open, i also could use 5 clutches. I have approx 800hp but low weight and no torque.
Last edited by Ck[FIN]; 05/27/12 04:01 PM.
-1965 Valiant 9.03s 358cu.in R5P7-
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Re: 727 question for experts
[Re: Ck[FIN]]
#1239392
05/30/12 04:16 PM
05/30/12 04:16 PM
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I assembled it with 5 clutches and plenty of clearance. Also drilled some bigger cooling holes. Then i checked all the gaskets/seals and the pump. Also made external oil pressure adjust hole. Next week i have time to put it back and give it a go.
Last edited by Ck[FIN]; 05/30/12 04:17 PM.
-1965 Valiant 9.03s 358cu.in R5P7-
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Re: 727 question for experts
[Re: Ck[FIN]]
#1239393
06/12/12 03:25 PM
06/12/12 03:25 PM
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Some updates, i measured the line pressure today and the pressure was about 175-180 in first gear. When i put it on 2nd, pressure drops to ~130psi and 3rd gear ~125psi. Rpm was about 2000.
I also measured front servo release port and it was same 125psi.
Should i have +170psi at all gears? Where should i try to find the leak? It seems to drop the pressure in 2nd gear already so should i find leak from front servo??
-1965 Valiant 9.03s 358cu.in R5P7-
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Re: 727 question for experts
[Re: Ck[FIN]]
#1239395
06/13/12 05:12 PM
06/13/12 05:12 PM
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John_Kunkel
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There are several places you could be losing pressure:
1)kickdown servo rings
2)accumulator rings
3)warpage at the surfaces where the VB mates to the case around the accumulator.
Since the pressure drop is near the same in 2nd and 3rd I'd look to the VB mating surface; any leakage there will affect servo apply and servo release.
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Re: 727 question for experts
[Re: rickraw]
#1239397
06/14/12 06:47 AM
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Thanks for the replies. I ordered dual ring accumulator piston and dual ring billet front servo from PATC. As soon as i get them, i change them and check the case to vb mating areas also.
-1965 Valiant 9.03s 358cu.in R5P7-
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Re: 727 question for experts
[Re: Ck[FIN]]
#1239398
08/16/12 03:20 AM
08/16/12 03:20 AM
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These parts didnt help much. First gear and transbrake pressed it has 175psi, 2nd and 3rd gear it drops to steady 125psi. Seems like its supposed to drop pressure like this. Maybe a time to try another vb?
Last edited by Ck[FIN]; 08/16/12 03:20 AM.
-1965 Valiant 9.03s 358cu.in R5P7-
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Re: 727 question for experts
[Re: Ck[FIN]]
#1239399
08/19/12 04:16 AM
08/19/12 04:16 AM
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Sweden
Tobbe
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sound like you have a internal leak ,i have made a adapter to my leakdown tester so i can test the ports in the trans (valvebody remowed) ,but that still not test the valve body in the past i have a weak shift to third (turbo action vb) and burned frictions ,change to a griner vb and that solved the problem ,have one teori about burnd frictions in 3rd when you have tranbrake or highstall do not the converter dumps hot oil into the area of the directdrum ? my trans was getting super hot in late rounds going bracketracing agains slower cars hade to whait at the tree at full stall (footbraking) one time i cracked a clutchplate 
Last edited by Tobbe; 08/19/12 04:19 AM.
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Re: 727 question for experts
[Re: Tobbe]
#1239400
11/08/12 07:42 AM
11/08/12 07:42 AM
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Ck[FIN]
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Found out the problem, no internal leaks.
Pressure drop is an feature in this cheetah VB. I contacted them and it is supposed to work like this. Pressure drop is made to improve ET`s and first gear pressure makes the transbrake engage faster.
-1965 Valiant 9.03s 358cu.in R5P7-
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Re: 727 question for experts
[Re: 440Jim]
#1239402
11/08/12 03:23 PM
11/08/12 03:23 PM
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Renton Wa
topfueldart
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Sounds like he's saying it was just low line pressure due to the design of the valve body to me.
11.48 @ 120 with a 1.80 60' 318, stock 1.88 heads, stock 904, Pump Gas, 13 lbs of boost.
9.94 @ 134, 318 on pump gas, 14 lbs w/ Eddies, transbrake 727, 3600 lbs, 3.54 gear and 28's.
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Re: 727 question for experts
[Re: Ck[FIN]]
#1239405
11/09/12 12:52 PM
11/09/12 12:52 PM
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440Jim
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Quote:
I have been told that usually 125psi is enough but maybe not enough in my current engine hp and rpm rate.
I asked that if the pressure could be changed in 2nd and 3rd but i got no answer from Paul at cheetah. Solutions seems to be A&A or Griner VB.
A valve body change would be the best solution, and IMO A&A, Griner, and TranzAct are good choices.
You could turn the line pressure up slightly (5psi maybe) by the adjuster. But with the spring and valve body valving it likely won't go a lot higher without a spring change in the regulator (where the adjuster screw is located). I think CRT sells a higher pressure spring for the regulator.
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Re: 727 question for experts
[Re: 440Jim]
#1239406
11/10/12 04:29 AM
11/10/12 04:29 AM
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Thanks for the tip, i ordered a regulator spring from John at CRT. It is a lot cheaper than new VB so worth of try. If it fails to work, i`ll have to order new VB. 
-1965 Valiant 9.03s 358cu.in R5P7-
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Re: 727 question for experts
[Re: Ck[FIN]]
#1239407
12/12/12 08:10 AM
12/12/12 08:10 AM
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New spring from CRT didnt help at this issue. Valve body seems to be calibrated to 125psi at 2nd and 3rd gear. I just bought Griner VB from this forum. I am sure this will fix my issues. Thanks for all replies. 
Last edited by Ck[FIN]; 12/12/12 08:11 AM.
-1965 Valiant 9.03s 358cu.in R5P7-
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