BKbroiler

Back in Oct/Nov last year I had a thread going here looking for theories about where 2 mph went on my last run on the track last year. I dropped from 110.5 to 108.5 with no apparent cause. After checking the engine, I pulled the trans and converter out, suspecting the converter. Sent it to Transmission Specialties. They cut it open, found nothing wrong, put in new bearings, welded up and returned it. I took my TH350 trans to Sepanic Racing Transmissions in Moosic PA. Jack took the trans apart and found evidence of slipping high gear clutches. He explained that the previous rebuilder didn't correctly perform the needed mod to prevent this. He did a full rebuild. I reinstalled everything, along with new 1/2 shafts and U joints. The car felt good on the street but I hadn't gotten to the track till today. Just test & tune today. I made 2 runs, both 12.40 at 110+mph, so the high gear clutch fix apparently cured the problem.

cardo0

Thx for sharing.

bluedawg

Hell yea! Now forward to 11.99 or better!

427Hotrod

Sweeeet! That will do it!

So what did he do for high gear? On T-400's I'd leave the center lip seal out of the drum so it applied pressure to the whole piston instead of just part of it in reverse and the other part in high. Slammed into reverse pretty hard...but that sucker never slipped in high gear with 2 stages of N2O feeding into it on top of a healthy Big block!

JIM

Les

Excellent! I'm glad you got it figured out. Now go kick some azz!

I won't make it to the strip this year but I just found out I'll be making some passes at our local airport for a Father's Day event. In the past it's been cars vs. airplanes but this year it looks like it'll be good old fashioned drag racing. Practice runs on Thurs. & Fri. with a Mustang GT500, a Camaro with nitrous, and a couple old school gassers. No idea how well any of them will get down the track....uhhhh, runway- but I'll know more when we're done playing Thursday. I may be the slowest guy out there but whatever the case it should be fun.

BKbroiler

Thanks for the responses guys.

Jim - My understanding of the fix was that there are 2 changes they do to increase fluid pressure on the hi gear clutches to prevent slippage. One of them is to restrict a bypass. That was not done in mine originally. My trans lived that way for quite a while since I'm only putting about 400 hp through it. So far so good.

Les - Good luck on that air strip. Could be a little tough traction-wise. I don't imagine they will be prepping it.

OMF

Sure would be nice to see you get that 11.xx timeslip....i'm sure we'll see a copy of it this year

BKbroiler

Thanks. Just for curiosity sake while I was on the DA calculator site, I entered my timeslip numbers from Sunday into the correction factor. I think this adjusts the numbers to correspond to a DA of zero. The corrected ET was 12.003. Close to 11 seconds in terms of corrected data, but nothing really counts unless its actually on the timeslip.

gveld

Good news you found your lost 2 mph . I could also say I have a 12 second car with 13.1 and 105 mph . Until I see that time slip it is still a 13.1 . Still having fun no matter what time slip says

BKbroiler

That 105 mph should get you into the 12s. I'm still thinking its camshaft or torque converter holding back your launch. Not easy fixes, I understand. Just food for thought.

Aggitated Monkey

Very impressive times! Can you share what the specs are on your car? Hp/tq read grear. I haven't ran mine at the track yet since building it last year. I have just over 1000 miles with no problems so far. Except for the tach. That's next. My engine is a 383 that dynoed at 496.4 hp with 468 tq. Trans is a 700r4 built for 650 hp 3000 stall and rear gear 3:70.

BKbroiler

I don't know my hp/torque numbers but I'm sure they're much less than yours. I have 3.73 gears, TH350, 3000 stall. Engine is a 383, ported Vortec heads, 225/232 duration hyd. roller cam, 9.7:1 compression, Qjet carb, 1 5/8 headers, 2.5 inch exhaust. I use drag radials at the track - that will be critical for you. BTW - I have run 12.15 in real good air. That's after a lot of trial and error.

OMF

I have to say I always look forward to reading your posts, as our cars are quite similar performance wise, and we both run vortec heads.
I'm most likely going to get some sticky tires to help with the spinning off the line, and am wondering if you have beefed up your driveline at all or if it's still stock?
I'll be putting a drive shaft hoop on, and a line lock to help warm the tires.

Alwyn678

Trans is a 700r4 built for 650 hp 3000 stall and rear gear 3:70.[/QUOTE]

Nice Tranny gear set-up! I have the same.

Your numbers are Very impressive and it sounds like there is even more room to improve

BKbroiler

Thanks. Improving significantly on the 12.15 would involve parts upgrading. I'm really hoping to get a 12.0 out of it - using real good air in the Fall and a little carb tweaking. (But that was my goal in 2015 and I didn't get there).

I have a driveshaft loop & half shaft loops - just for peace of mind, and a line lock. Drag radials can take 5 tenths off your ET and make your times consistent.
As for beefing up the drivetrain - I have a GOOD torque converter. Originally had a B&M and broke that. Trans is redone by Sepanic as a street/strip unit. Shifts automatically - even on the track. Spicer solid U joints, all six. I had stock 1/2 shafts, no problems, but I replaced them recently with new ones from Fort Wayne Clutch. They come with the flange and u joints installed. I have Drag Vette billet caps replacing the u bolts on the inner u joints. The rear itself was rebuilt by Bairs with Strange 3.73 gears. Overall, not very exotic, but I have 241 runs on the car now, starting at 14.0 and working down and I've always been able to drive it home. But really, my goal is consistency since I enjoy bracket racing.
Post up your results when you get to the track.

Aggitated Monkey

Very nice numbers. Give me something to look forward to. I've done a couple launches on back roads and it a little squirmy. Fishtails a little. My 383 is 10.5:1 and cam is 530 lift. Don't have the rest of cam specs with me. Getting old on memory.

OMF

Well..... I did get to the track a couple of weeks ago, first time in 37 years.
I did 9 runs, and the best I could do was a 13.80 @105.
Most were in the low 14' due to missed shifts (2nd to 5th and back to third on three occasions ), spinning off the line, or general lack of skill....
Had lots of fun though

BKbroiler

Oh, manual trans, much cooler but much more difficult to launch, as you know. About your 37 years away from the track - you have me beat. I was away about 30 years before I started racing my C3. I never expected to get back into it as much as I have, although I don't race nearly as much as I did back then. BTW - that 105 mph could get you in the 12s if you could get your 60 ft times down to 1.8 or so.