200 4r Mystery Failure

[Paul Martin]

Hi Everyone,
First a little background, I have a 1951 Cadillac Series 62 Sedan "resto-mod" daily driver/hot rod. The motor is a SBC 355 with AFR Vortec street level heads, roller rockers, Lunati Voodoo roller cam, 10.97 CR, Holley Terminator TB-EFI system, a CPT (the real Art Carr) 200-4r stage II+ transmission with the non-lockup 11" TC. I put the 200-4r in about a year ago, and it was AMAZING! complete blew away the TH-400 I had been running at first. The only issue that I ever had, and had from the get go was a super minor leak, on the passenger side of the case (I thought from the pan seal), and truly minor, every month I'd had to put in 100 ML to keep the transmission at the perfectly full mark. In the last year I put 10,000 miles on the car, mostly city driving but also some occasional vintage auto-cross runs. It has always had the setrab cooler with 2x 400 CFM fans, and the TV cable has always been set correctly (Note: I snapped my first one about 4 mos ago, but pulled over instantly and butt spliced it and re-set it correctly, then replaced it). It's never been run with the fluid level low, nor has it ever been run without the cooler. About a week ago I was driving home on the Toll-way sustained at 84 MPH, (2800 rpm in 4th) and all of a sudden it started to slip like crazy, felt like I had it in N. I pulled over, checked everything, no sign of an issue, fluid level was in spec, TV cable was perfect. I tried all gears. If I have it D (3) it shift and drives perfectly, no slippage. Same for 2 & 1. However as soon as it goes to OD (4) selection is slips in all gears. Also the R is slipping just like OD. The next day there was a rather large spot of transmission fluid on the ground. After further inspection, it seems to be coming from the servo cover. That may explain my lingering leak (I replaced the stamped pan with the deep finned AL pan, used the CPT recommend gasket with gasket shellac, even re finished the mating surfaces and made sure they were 100% flat as the tiny drip was driving me nuts). I called Art Carr, and he conference called me in with the tech that built my transmission. They both could not advise what had happened, and also noted they never had one of their super servos ever leak in all these years. I live in CO so I can't take the transmission to him to inspect. I have an appointment next week with the best 200-4r builder in the state of CO to do a line test and discuss a potential rebuild, if need, as, although I have a warranty with CPT, the cost of shipping and parts, per the terms of the warranty, is a wash with a local re-build. Moreover, if I do ship back to CPT I'd lose a month of peak show season. So here is the question HOW can I slip in all gears in OD (and slip in R) but 1, 2 and D are perfect, snappy, sharp and fast as ever? Any thoughts? I know y'all here are the most informed on the 200-4r and I read a ton of your posts when picking the type (200-4r) and the provider (CPT).

 

[TexasT]

sounds like the od clutches have been torched. many builders cut the od piston .080 and put an extra clutch between the steels without one(the you have 50% more clutch area).
get a gauge on it. low pressure could also be a problem.

 

[INEEDAGN]

When you move the shifter from OD to d you get a boost in pressure as well as the overrun clutch pack applying, which basically overrides the sprag (which is a one way clutch and is why the engine can coast down in overdrive but has engine braking in all other gears). Does it slip during takeoff from a standstill in OD or d range?

 

[INEEDAGN]

Double post

 

[Paul Martin]

sounds like the od clutches have been torched. many builders cut the od piston .080 and put an extra clutch between the steels without one(the you have 50% more clutch area).
get a gauge on it. low pressure could also be a problem.

Yeah, Monday I start with the line pressure test at the transmission shop. However, if the od clutch is blown, how does that also kill reverse? I looked at the diagram of all the components and I don't see any od and r cross over usage. Now I will state, I am a transmission novice, and have spent the last week on a crash course of learning slush boxes. Did I miss something?

 

[Paul Martin]

It only slips when in in the selection of od or reverse, and slips quite badly. On a flat surface it's rev-ing up to 3k before any movement at all, and that movement is super reduced, just like an on a manual when the clutch is mostly engaged. In drive aka 3rd, it does not seem to slip... Well as the torque converter is a higher stall (brake stall typically, before this all happened was about 2700-2800 and flash stall slightly higher) under wot it feels roughly the same, but until its up to almost 3k, as always, you notice the tc multiplying and the feel is similar. I've not been pushing the transmission too much on the few test drives since the failure as I would like to be able to get her to the shop on Monday without a tow(I'm pretty convinced that a major fix is in the cards here and don't want to press my luck).

 

[Paul Martin]

Note: feel is similar, aka like a clutch engaging on a manual, but in od or r its a constant 90% clutch in feel. If I'm in d, 2 or ,1 it's the normal, progressive release I'm used to with this transmission when it was not unhappy. One thing is, cpt set the governor to my specified 6500 wot shift point, so I always had the car in od. At that configuration, with the TV set per cpt (no slack at pedal fully down and about 1/4" preload, you can feel a slight difference between the preload and actually fully pulling the spring) she would stay in gear until 2800-2900 before changing up; even when a wot to full off the pedal move was used.

 

[Paul Martin]

One more note so I'm clear here. In d, 2, or 1 if I flash stall off a stand still, right now, over 2700, I will still burn rubber, just as normal, I have not done a full power pull since the failure, but I can tell, in d, 2 or 1 she feels normal. I can, from past experience, stall her up to 2800 pop off the brake and roll on the gas and maintain a full traction loss/burn out all the way through 1, 2.and 3 with a nice chirp into 4. (Running open 3.73's with 245 45r20's.)

 

[Paul Martin]

ok one more and I'm off to bed, have to work tomorrow... But I thought I might give you some pix of my baby.

 

[David Husek]

From your description, I would say the OD Sprag has failed. The OD Sprag is bypassed when in the Drive range and is not used when the trans shifts into 4th gear. This is why you can shift it up thru all the gears like normal. It is also used when in Reverse range. I doubt you have any clutch failures. If the sprag has failed, it is an easy fix. The OD carrier can be damaged so be prepared to locate a few replacement parts. I can supply then if you cannot source them locally. The OD Sprag takes a beating if you run it thru the gears without putting the trans in the Drive range especially with extra RPM(6500). Always best to start in 2nd range and manually shift up but definitely at the least start in Drive.

 

[Paul Martin]

Oh, thank you so much, that makes sense. I've always had manual gearboxes until now, never knew that about od... Now I get why oems had a button on some of the od transmissions for the od. I just assumed that being a non-lock up keeping it in od was fine. You guys rock, I haven't slept well all week worrying about my baby! I'll update y'all when we get it apart Monday... Whew! I was going nuts trying to wrap my brain around this.

 

[Paul Martin]

Well, David you were 100% right. The OD sprag was indeed the issue. Again, thanks so much for your help on this, you guys on this board are AMAZING! I should have the caddy all fixed up and on the road again by Friday. No more OD launches!