R&P cuts... Whats teh strongerest...

[boredandstroked]

Okay opinions on what is the strongest R&P or if you like C&P. For years I believed the 3.88G was the best for drag racing. Now I am starting to think maybe it isn't the strongest for drag racing. Any one have experience with the 3.88K ? What about a 3.88O anybody every actually seen one? The 3.88 has the largest pinion head of all the type 1 pinions, but also the thinest ring gear. So what is the best 3.88? As for 4.12 and 4.37 ratio the G in both is fairly weak, especially the 4.37. The K in both is fairly strong and I think a 4.12 K probably has a stronger pinion than the 4.37 K, and all of those a believe to be weaker than a 3.88 G. I could go on but I really want some input on the "order" of ring and pinion strength other believe in. Especially when comparing a 3.88 G to 3.88 K in drag applications.

[Tom Notch]

strongest? simple- 4.57

[Frito Bandito]

I have read that the klinkinberg type gear cutter is by far a more acurate tooth cutting machine however it is very sloow. So for production and profits companies use a gleason type machine which takes a lot longer to set up so that is why they have to run min of 150 sets at a time. Now like I said I read this somewhere and when I find it Ill post the link.
I know that this doesnt say anything about stronger but if the root of the tooth is smooth and with out ridges like the G has then IMOP it has to be stronger. We can deburr edges on the outside of the teeth but not down in the root, and if so Please let me know how?

I have been a fair trans builder but have gottin so pisssst off with quailty of used wore out parts Ive all but givin up.

Gary

[boredandstroked]

strongest? simple- 4.57

I think the 4.86 or 4.12 would beat it. Those being in a Mendola of course. Type1 is the topic at hand.

[boredandstroked]

I have read that the klinkinberg type gear cutter is by far a more acurate tooth cutting machine however it is very sloow. So for production and profits companies use a gleason type machine which takes a lot longer to set up so that is why they have to run min of 150 sets at a time. Now like I said I read this somewhere and when I find it Ill post the link.
I know that this doesnt say anything about stronger but if the root of the tooth is smooth and with out ridges like the G has then IMOP it has to be stronger. We can deburr edges on the outside of the teeth but not down in the root, and if so Please let me know how?

I have been a fair trans builder but have gottin so pisssst off with quailty of used wore out parts Ive all but givin up.

Gary

That info probably came from Weddle. Of course I agree that the K is better in the 4.36 and 4.12 than a G but I am not so sure about the 3.88. The K also has an even tooth angle and has a broader range to set the pinion depth than the G. Do you have personal experinece with the 3.88K?

[Roland]

I must say that i have had greater success whith the 3.88G than whith the 3.88K. Last weekend i ripped all the teeth from a 3.88K, that have never happend to me whith a 3.88G. //Roland

[Pablo]

The strongest 3.88 is the 8:31G -- far stronger than the 8:31K. This is the strongest Type I R&P.

The strongest 4.12 is the 8:33O -- very close in strength to the 8:31G. The 8:33K is somewhere between the O and the G in strength.

The strongest 4.37 is the 8:35K. The 8:35G is the weakest.

[Carl Nolen]

Drag race r&p talk. My favorite or least favorite subject. Just depends if I broke one recently or not. The phrase" bigger is better" or "it's not how big it is, it's how you use it". I heard those somewhere. Both can apply. Back in the stoneage when I started drag racing VW's, I did start with the 4.37 and four spider add on shaft. Really did not run the 4.37 long enough to get a feel for how many passes they would take. I was breaking other trans idems at the time. I first started out with the 180mm porsche pp with solid regular disc. That was the hot clutch setup back in the day. Really did not start breaking things until I put a 2300 pp with three puck disc in. But, that is another subject. Anyway, I changed over to 4.12 in the mid 80's just because I was told it was stronger than the 4.37. Just trying to build a better box at the time as aftermarket parts became readily available. After I changed all the weak stuff to berg axles, spool, super beetle first gear, I started breaking 4.12 r&p. Broke three of them before I was told I was running too much clutch(another subject). After I replaced the clutch with a 1700-four puck setup, never broke another one. During the 90's, I would get 120 or so runs out of a 4.12. I did run a G & K at times. Really did not notice one being stronger than the other. About the same life. Never did hear any noise from the box, just wanted to service it before a problem happened. Always the same wear pattern, cracking about 3mm down from top of tooth with a crack line toward bearing area of the pinion. Don't seem to remember a problem with the ring gear, always the pinion. This was in a 1550lbs car and driver with a 78x94 motor doing 11.80 or so. I purposely used a 78 stroke to cut down on the torque applied to the box. Plus, you can get away without wedgemating on 78 stroke(another subject). As time went on, I started cracking cases. Welded gusset fixed that. So, I really had no problem with the 4.12 or super beetle mainshaft with this clutch/motor power setup.

Switched over to the 3.88 with 4.11 manshaft in 98 due to changing a couple of things on my car. Increasing horsepower and installing delay box with clutch release(evil electronics ya know). My first 3.88 lasted 60-70 runs or so. I had broken an old diamond axle and noticed cracking while looking over trans while chaning out the axle. Probably could have put 70 more runs on it. Put in a new r&p and snapped it like a twigg first time back out. I broke it due to the clutch release allowing the clutch to engage too quickly. Fixed that and replaced r&p. The next one, I left in there until it broke to see just how many runs I could get on it. Went 200 passes with way too many dry hops trying to get the old firestones to hook up. This was telling me the clutch release was acting as a anti-shocker when I slowed to pedal speed way down. Replaced that one and let my young son make a pass. I told him just to ease the clutch out and go through the gears and he would run a seven second(1/8) pass. So what does he do? Revs that sucker up to 8000 and side stepped the clutch. Snapped like a twigg. Oh well, chalk it up to inexperience. I got 140 passes on the next one and started making loud gear type noise last June. One this last r&p, the teeth on the pinion were breaking at the root of the tooth up by the pinion. You could not see it until you removed the bearing. Did not break the teeth off. Laid them over pretty good. Ring gear looked just fine. No cracking anywhere.

So long story short, the 3.88 seemed to give me more passes before servicing. The 4.12 would be just fine but may need servicing sooner. By the way, I have seen two 4.57 r&p break like a twigg two weeks in a row a few years ago. Several racers here in Texas run type 2 boxes and I have seen a lot with those. The r&p breakage was due to clutch release speed being too fast. These clutch release systems can be trouble if not set just right. Most of the problems I have seen with bus trans is the U joint on the Folts axles. May be like r&p's. They need replacing after so many runs too. Good luck this year boredandstroked. Seen you car in pictures on the net lately. How's everything going this year? Later, Carl.

[Bruce2]

I was talking to Eric at ERCO about this. He said the G831 is the strongest of all. Then "almost as strong" is the O833. He said the K831 is a dog.

I have a friend in Sweden who has seen an O831, but we don't know it's strength.

I recently found a 0835, anyone know where that would stand on the pecking order?

[Pablo]

That's an interesting find. Does it use "standard" ring gear bolts, or the small diameter ones?

[Frito Bandito]

Do you have personal experinece with the 3.88K?

Only once. Back several years ago I bought new GB660K-3.875. It used the 9mm ring bolts 8 ea. Well I took it to a heat treat shop and had it taken from 62 rockwell down to 57 rockwell. The man was an old school drag racer and knew what hardness the drag gear sets were. He told me that I wouldnt break this R&P but would wear it out . However, I would have to adjust backlash as the set wore. This R&P went into stock gusseted case with one HD sidecover JayCee cloverleaf spool ect. with 2300# and 6 puck in my 1625# car running 10.70s on NOS.
Well I did not heed tha mans warning about backlash and pinion let loose at 180 passes. I feel had I corrected backlash as instructed this set would still be running.


This is the only one (K) I have had. So that is why I voted 388K.

Gary[/img]

[Bruce2]

That's an interesting find. Does it use "standard" ring gear bolts, or the small diameter ones?

It uses standard M10 bolts. It's a German 8 bolt R&P.

[Guest]

I just bought a "o" 3.88 from Erco about 2 months ago.It went out of the country,Would like to know how it holds up.

[kcr]

That was me,not logged in.

[boredandstroked]

If you or anyone else can get me a 3.880 I will pay top dollar for it and give it a good round of testing. I can perform several metallurgical tests on it and beat the hell out of it . I am approaching 50 passes on my 4.120. I think the 4.12 is too low for the torque of the engine I am running now and I am considering running a 3.88 again. A 3.88 O would make the choice easy. I have had to lift on the last 3 passes when the ass end tried to fish tail. So I am sure the R&P was wounded from those and I don't plan to try to go past 50 on this R&P. I have an outstanding 3.88G and 4.12O on standby but I'd love to try a 3.88O.