I just put a wicked 3800 stall Coan converter in my Riv. The car is now unreal. It launches so hard! I love it! But... What I really hate is this: when I slow down to a very slow speed in traffic or to make a turn, the trans just won't pull down into 2nd gear. It hangs in 3rd gear, and when I accelerate to get up to traffic speed (like to 35 or 40 MPH) it really winds the motor and the car pretty much doesn't go anywhere as the conveter is slipping (like it is supposed to do). Any thoughts on what I can do to get it to downshift when I come almost to a stop? I hate to keep having to pull it back into 2nd gear to help it accelerate easier. When I stop, it DOES drop into 1st gear by itself. I have turned in the adjuster on the vacuum modulator and I DO have power at the kick down, as it kicks down at about 30 MPH or so. Any ideas???
I am NO expert but I have rebuild a couple of automatic transmissions. Since no real experts are talking yet I got out my book and looked at the THM400 diagnosis chart. The closest problem I could find to what you describe is "No part throttle downshifts" Condition (a) "3-2 valve stuck, spring missing or broken." Correction "Free valve and or replace spring." Condition (b) "Oil pressure incorrect." Correction "Check operation of vacuum modulator assembly and replace if necessary." Before I looked this up I thought since you just replaced the converter, some sort of trash may have gotten into the system and caused a valve to stick. If everything was shifting normally before the converter change, this seems logical. The modulator is easy to change though so you could try changing that anyway with a known good one to eliminate it. I had a valve get sticky once and I thought I could take the valve out, clean up the bore and the valve and it would be fine. It got better but I wasn't happy with it until I changed the valve body. If it was me, I'd call Coan in the morning and ask them their opinion as well.
Jeff, Check the rubber line that goes to the modulator valve. It very well could have a hole in it from a header tube, or wear thru. Also, check for proper modulator valve operation. Also, pull the governor and clean it with carb cleaner. Then, hold it by the gear, with the weights hanging down (gear up, weight end hanging down). Move the weights in and out, and look CLOSELY at the small valve inside the governor shaft to make sure it is moving up and down freely as you move the weights. If it is not moving freely, clean it again and/or disassemble and repair. If you disassemble the governor to clean/repair, I usually put a very small spring inside the shaft to "help" keep the valve moving freely. Or you could send the gov to DeConti or another trans guy to rebuild, or send it to me and I will do it for you. It isnt difficult if you have a very small punch to remove the plastic gear. As the trans spins the gov, the weights move outward, which in turn moves the valve inside the gov, allowing for gear changes. Which is why you can shave weight off the gov weights to increase gear change rpm, or add weight to lower rpm. If the valve isnt moving freely inside the gov, the rpm will be too high at gear change, and the trans wont downshift properly at lower speeds either. I would about bet dollars to doughnuts the gov is the problem. It either has a piece of trash in it, or a burr keeping the valve from moving properly. Simple fix. Let us know what you find.
Might want to possibly consider the same stall but with a switch pitch. Low stall for traffic and high stall for the strip. Just a thought. John.
Yards - try calling Chris 718-784-4256 or 631 218 1989 at CK Performance - they are pretty helpful and may have a suggestion. - Bill
X2 The gov is the issue. mine was doing the same thing. I cleaned up and put heaver weights in and middle of the road springs with a b&m kit. i had the weights trimmed to much. I need to get gears in it and get it off the jack stands try it.
Thanks all. This is an issue that only surfaced the minutes I installed the converter. I changed the fluid and filter last night. The fluid smelled burnt. I hope I didn't burn the fluid as soon as I fired it up with that small converter. As much as it slips I can assume it will generate a lot more heat??? The governer may have had a sticky valve. So I cleaned it real good and put it back in. I'll road test it later today and see. I'll keep you posted. I'm hoping it is just coincidental that the trans started acting up at the same time as the converter change. Jim, I didn't swap governers because at the last minute I remembered that the other governer shifted higher than my self-imposed red line of 5000 RPM. So that's why I cleaned the one that was in there and reused it.
Yards, Call Coan, it shouldn't feel like it slips that much. It probably needs an adjustment. They will make it right.
I was under the impression that the big name high dollar converters didnt do that and you only noticed that you had a high stall converter when you were really on the gas.o No:
That is correct. Something is not right. I told him to make a phone call. It should not feel that loose.
8" x 9" ... one row. After discussing this with Wizard, Alan and my buddy with a 9 second Camaro, it is obvious by it's performance that it is slipping very badly - not locking up at all in any range. Just rolling it up my floor ramps saw 3000 RPM! My cruising RPM has increased by almost 500 RPM. Driving it home from Reader's Digest completely FRIED the trans fluid. So much so that the trans refused to pull back into 2nd gear when I slowed down to a near stop. I'm PRAYING that it is a governer problem (I took it out and cleaned it thoroughly), so we'll see. At any rate, best case scenario: Coan makes good and does the right thing. Worst case scenario: my trans is fried due to the burnt fluid running it it for about 100 miles, and Coan won't step up. We'll see. But the bad part now is, I won't know if the trans is OK until after I put in another new converter and drive it. Oh goody... I get to do my SIXTH transmission lying on my back all in ONE YEAR!
Hey Jeff.Sounds like you need some time with a garage with some type of hoist when you get the new converter.If you have to re & re the trans twice..why kill your back??..I wouldn`t.Keep us posted my freind.Later,Tony.
Just my opinion, but burnt fluid= burnt clutches. It would be cheap insurance to pull the pump out and take a look. The least you'll be out is a pump gasket, the most you'll be out is some clutches (or overhaul, if you choose). The peace of mind of knowing for sure will be priceless.
I would not recommend jumping to the conclusion that Coan did something wrong. Be humble and listen carefully and be ready to blame yourself until you are absolutely certain what the cause was. It would be hard to blame a burnt trans on a converter swap, and never heard of a converter burning fluid all by itself. Seems there must be something else that contributed. Trouble getting the converter on the pump, or not fully engaged with the pump? HP converters don't fit nearly as tight between the trans and flex-plate as an OEM because they want plenty of room for a little bit of converter ballooning without taking out your thrust bearing. So there might have actually been a little too much clearance? Just brainstorming here...
Like I said, it's just my opinion. I think you are capable enough and have enough resources to at least do an inspection on your own trans. You wouldn't need any special tools to just disassemble enough to inspect the clutches. http://www.v8buick.com/showthread.php?t=69003&highlight=trans+official. I really think the peace of mind of knowing would be worth it.
I toasted mine back in the '80's after raising the high stall on my switch pitch. Remember back when Kenne-Bell said you didn't need an external cooler for vp? :spank: Added a small external cooler, promptly toasted it again. I now run a temp gage, bigger external cooler and have bypassed the trans cooler in the radiator. Lessons learned - The small cooler wasn't enough for my driving habits Not having a gage meant I had no idea what was going on Don't believe everything Kenned-Bell prints Devon
