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620 Land Speed Record


distributorguy

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You could get a Winters quick change axle. They make a lightweight axle that can handle up to 300 hp. Not exactly cheap though.

 

I would be wary of a Dana 44 or 12 bolt, as gear ratio changes will be much more difficult. You could preset a few different r&p sets, but they're still a pain to swap in a hurry.

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I don't think I'm allowed to use a quick change in production class - plus they sap a lot of hp that we can't spare.  Only 230 hp or so, and no traction so I'm not too worried which axle we can fit.  If they are cheap, we can bring an entire assembly and swap the works.  

 

Mike, is that ZX ratio with the 1.858 or 2.077 2nd gear?  

I only have a 4WD trans, so I'm not sure how I'll get this set up.  Its a nice progressive ratio trans however, and would be ideal for land speed racing.  Can you build us one???  I'm about to go out and check what exactly we have.  

 

So our 720 trans (with 1200 miles on it) is a wide ratio with a 3.59 first gear.  

Then we have the odd duck that came out of the truck.  The case number is 7Z31794, if I read it correctly.  Not sure what it is but the front upper gear is 21 tooth, the lower it engages is 32 tooth.  Its still partially assembled and I have no idea how to remove the rear case.  

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Wide Ratio input gears 21/32 or 1.523 x other gears

 

1st... 33/14 or 2.357 X 1.523 = 3.592

2nd... 27/20 or 1.350 x 1.523 = 2.057

3rd.... 25/28 or 0.892 x 1.523 = 1.359

4th.............................................1.000

5th.... 24/45 or 0.533 x 1.523 = 0.812

 

 

Mid Ratio input gears 22/31 or 1.409 x all gears

 

1st.... 33/14 or 2.357 x 1.409 = 3.321

2nd... 28/29 or 1.470 x 1.409 = 2.076

3rd.... 26/28 or 0.928 x 1.409 = 1.308

4th............................................. 1.000

5th..... 19/31 or 0.612 x 1.409 = 0.863

.

 

Close Ratio (ZX) input gears 23/29  or 1.261 x all gears

 

1st.... 34/14 or 2.429 x 1.261 = 3.062

2nd... 28/19 or 1.474 x 1.261 = 1.858

3rd.... 28/27 or 1.037 x 1.261 = 1.308

4th............................................. 1.000

5th..... 26/44 or 0.591 x 1.261 = 0.745

 

The 1 through 4 gears cannot be changed but we can swap the input gears and the over drive 5th gears. For example,

 

if the wide ratio inputs were put on the zx close ratio the first gear becomes 3.699!!!! really wide.

If the mid ratio inputs were on the zx, first becomes 3.422 a sort of half way between wide and mid.

 

If the zx input gears were on the mid or the wide ratio both would have a 2.972 first gear. Tthe RED ratios are the same

 

The wide and the mid that I have, have odd OD 5th gears, that if you put the zx inputs on them produce a  0.672 and 0.772 respectively

 

* there are for sure going to be exceptions to this. I don't have every gear box made.

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A progressively tighter gear spacing working toward 4th gear would be ideal.  We spend progressively more time in each gear now, and it would be ideal for 3-4 to be a very short jump.  The 720 mid-ratio trans with ZX inputs seem to be a pretty ideal spacing for this style racing.  Likely no good for any other racing, but for LSR it seems ideal.  

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The problem with the D44 Wagoneer axle is that they are becoming hard to find because every CJ owner wants them.

 

If you do end up with one, presetting gear sets would not be a lot of work. Then if you need a R&P swap, you know already which shims the new gears will need.

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I don't think the Jeep guys want the gear ratios i'm after - so it may be easier to find them.  There's a local place that makes a LOT of off-road Jeep parts and they constantly have a Craigslist ad for oddballs.  

What's the width difference between a stock 620 and the Wagoneer though?  I don't have much room to spare.  I could stand to go a little narrower.  

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So Mike, I called my transmission guy today (owns a TSI transmission shop) and he was concerned that the ZX input shaft won't mesh with the 720 trans.  Is this a possibility due to gear count?  It looks like there may be a few 720 transmissions available locally - one as cheap as $65.  Hopefully at least one of them is a mid-ratio?  Will know soon.  

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The input shaft is all one piece from the clutch spline to the gear on the back that mates with the counter shaft gear below it. They are a set. The counter input gear is pressed onto the counter shaft spline. At the very back of the input shaft and the very front of the mainshaft is where the 4th 'gear' is. Forth is just the joining of the input shaft to the mainshaft. They should swap as a set..

 

The transmission must be from a Z24 2wd to get that ideal 1.902 2nd gear ratio. The Z22 2wd is also a mid ratio but has the 2.071 second with the big drop into 3rd.

 

 

edit: Add the '79 280zx 5 speed to that list of transmissions with the 1.902 second gear ratio.

 

1st... 3.321

2nd.. 1.902... 42.8%  Normally this is a 2.076 

3rd... 1.308... 31.3%* and a 37% big drop into 3rd

4th... 1.000... 23.6%

5th... 0.382... 13.7%

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So Mike, I called my transmission guy today (owns a TSI transmission shop) and he was concerned that the ZX input shaft won't mesh with the 720 trans.  Is this a possibility due to gear count?  It looks like there may be a few 720 transmissions available locally - one as cheap as $65.  Hopefully at least one of them is a mid-ratio?  Will know soon.  

You do understand that the input gear needs the corresponding gear off the cluster to go with it, right? You can't just swap in a new input gear.

 

As far as I know, all gears and parts are interchangeable among the same transmission family line. They did make some changes over the years to synchros and shift forks, bearings too, but the gears should all be interchangeable.

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I don't understand anything about how this works, but my transmission guy does.  Its a pretty simple system that I've never taken the time to learn, nor do I want to corrupt what little I can remember day-to-day with even more new info.   :crying:   I look at transmissions the way many people look at distributors - leave it to the professionals.  There's a little voodoo in there that if its not right, it'll get even more expensive later.  

If I had the cash, I'd buy a Lenco 4 speed.  at 2.46, 1.80, 1.31, 1.00.   Or a Liberty 5-speed with 1:1 5th.  

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That's my understanding also. My '85 transmission has huge aluminum forks and the synchro rings look similar but the synchro hub is way different.  Haven't checked but maybe this weekend I'll measure the counter gear cluster and the mates to them on the main shaft to se if they are wider. It does have the larger 62mm counter bearing.

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There are probably other options, but the Saenz is pretty light and comes in many different configurations. They have direct drive 1:1 5th gear. I found a used one with Nissan bellhousing for $3500, but sold. http://www.race-cars.com/boxsold/other/1205726392/1205726392ss.htm

 

Comparing prices, a Nismo DD 5 spd sells for $2K - $3K. I'd rather have something modern that you can still get parts for.

 

Here's a Nismo ultra close OD Roadster box for over $2k - http://www.race-cars.com/boxsales/other/1501636369/1501636369ss.htm

 

...and another one for $4K - http://www.race-cars.com/boxsales/other/1489787049/1489787049ss.htm

 

What happened to your BMW trans idea?

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Or a Nissan ZEOD RC 3 cylinder turbo with 400hp???

https://www.autoblog.com/2014/01/28/nissan-three-cylinder-race-engine/

 

The BMW trans ratios aren't as good as I thought they were, and I'm still fighting to find someone local who can build AND balance a driveshaft properly.  I'm simply looking for a better and easier swap.  The clutch arrangement would have been a nightmare anyway.  Doable, but very time consuming and expensive.  Given how much work the scattershield was, I'd like to use it one more year.  I'm not convinced that the trans is really a big shortfall, compared to the diff.  

 

It appears my diff is roughly 54" wide, so I'd like to find something in that range, or ???  Jeep Cherokee and YJ/TJ seem to be close, but they don't seem to use the high ratios I'm searching for.  Otherwise it'll mean custom.  

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Yes, you should be able to run a 4 speed and just eliminate the overdrive altogether. How many Muncie 4 spds do you think are out there behind small block Chevys? Probably a lot.

 

Jeep Dana 35 axles are generally regarded as garbage, but that's in the context of rock crawling. For what you're doing, it would probably be fine. They are cheap, because many YJ owners ditch them in favor of D44's or Ford 9" axles, and there are quite a few upgrades available. They are 5 lug though, so that's worth considering. You could very easily re-drill the flanges and drums (or rotors) if that bothers you.

 

I found R&P sets all the way down to 3.07 here on Randy's website - https://www.ringpinion.com/b2c/PartsList.aspx?SearchMode=Cat&CatID=35&MakeID=7&ModelID=394&Side=Rear&DriveType=4WD&DiffID=236

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I think I found the perfect axle for you.

 

Chevy S10, 83-04, 2WD, 7.5" or 8.5" diff - 54.25" wide.

 

The later trucks came with rear discs and I think they were 6 lug stock (I know the 4x4's were).

 

Randy's sells R&P sets all the way down to 2.73 - https://www.ringpinion.com/b2c/DiffList.aspx?SearchMode=Cat&CatID=35&MakeID=3&ModelID=324&Side=Rear&DriveType=RWD

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Most S10s (if not all) were 5 lug - I owned a few.  But that's one of the easier things to correct.  I'll check some local junkyards.  That's the axle I run in the Willys pickup as well.  Also disc brakes.  

Thank you!!!

 

The problem with a 2.73 is that unless we get better traction, that would put us at 130 mph exactly, given our "on-track" correction factor - makes it difficult to break a record, but competitive.  I wonder if I could swap the center section from my Olds into that axle?  I have a 2.56 lying around.  Damn close.  Looks like THE housing option, although will require C-clip eliminators, a spool, and redrilled axles or new wheels.  

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