240Z Fellows - Some guidance?

I have two gear boxes for my Jensen - a four speed and a five speed. I can legally use both, the JH had both boxes in the US with no name change on the car or anything like that. I understand the 240/260/280 changes preclude 240 folks from using the update/backdate rule to run a five speed. Five speeds for the JH appeared in 1975, while the four speeds ran from 73-74.

Both boxes have a 1:1 top gear. The 4 speed is stronger than the 5 speed. 4 speed is a Chrysler small car/truck box, the 5 speed is a Getrag piece that grenades a lot, according to JH folks. 4 speeds are like a&*holes, 5 speeds are like rocking horse sh*$.

My question is this - how do you 240z folks get along with a 4 speed box? Any tracks that pose big problems (I'm in the SE)?

Thanks,
Ron

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Ron
http://www.gt40s.com
Lotus Turbo Esprit
BMW E36 M3
RF GT40 Replica
Jensen-Healey: IT prep progressing!

[This message has been edited by rlearp (edited October 28, 2004).]

Ron, since the diff ratio is free, most Z pilots that I know run different ratio's for different tracks. Since it's an IRS setup, changing the diff isn't a real big problem.

Like the 510 in ITC, changing the pumpkin is standard for each track. Here in San Francisco, I know that they use 3 different rations for each track: Laguna Seca, Thunderhill, and Sears Point. I still can't call it "Infineon" just yet. It doesn't "come off the tongue" very cleanly.

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Tim Linerud
San Francisco Region SCCA
#95 GP Wabbit
http://linerud.myvnc.com/racing/index.html

[This message has been edited by racer_tim (edited October 28, 2004).]

Different ratios is cool but I have only 3 to choose from and the best one gets me 135mph at 7200RPM. So, that is best for me and in my car. Mine is welded now too, so I'd have to have 2 complete rear ends to bolt in and out. Not that hard actually and I could do it.

Any opinions on driving a four speed? Is it a big disadvantage having only 3 gears to use on the track? On paper it seems to be horrible, but in practice I just don't know.

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Ron
http://www.gt40s.com
Lotus Turbo Esprit
Ford Lightning
RF GT40 Replica
Jensen-Healey: IT prep progressing!

[This message has been edited by rlearp (edited October 28, 2004).]

[This message has been edited by rlearp (edited October 28, 2004).]

Hi Ron,
I would lean towards trying the 5-speed myself to allow using a 4.11 or 4.35 rear ratio....I would compare to actual ratios to determine if actually any diffference....other then the 5th"overdrive"?allowing use of shorter diff, that would in it self be worth quite a lot....if the 240 crowd could use over drive 5 speed, it would help with some of our power complaints...oh yea, vented front rotors too...while I'm dreaming.
7200 RPMs from the Buick V-8? Wow...Be at VIR this weekend?
David Spillman

Keep dreaming Dave.....
While you're at it, you might as well dream about having the 280ZX solid rear discs and 200SX calipers too.....LOL

Hey David,

You've got me confused with Jeff. My car uses a Lotus 4 valve four cylinder that is very oversquare. 7200 RPM is no problem for it, in fact, if it'd breathe the red line should, according to the engineering aspects of the motor, be around 8100RPM (based on stroke, valve masses, spring rates, etc.).

I've got the shortest (highest numerically) gear possible in the rear end - it is a strange rear end out of a Vauxhall Droop Snoot Frienza, of which you can imagine there were not many made. It is around a 4.11 as I recall.

I have compared the ratios and both top gears are 1:1 while the 5 speed just has slightly shorter bottom 4 gears than the 3 speeds bottom 3 gears. Neither box is an overdrive top gear.

Jeff said he will be at VIR this weekend and I plan to be up there spectating.

Ron

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Ron
http://www.gt40s.com
Lotus Turbo Esprit
Ford Lightning
RF GT40 Replica
Jensen-Healey: IT prep progressing!

[This message has been edited by rlearp (edited October 29, 2004).]

[This message has been edited by rlearp (edited October 29, 2004).]

At the tracks I run, I use 4th and 5th at most unless there is a very slow turn (6 at Barber) and then use third. The Z car guys use 2rd, 3th, and 4th at Barber. Number of gears doesn't have much bearing...just the spacing.

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Chuck Baader
#36 ITA E30 BMW
Alabama Region Divisional Registrar

I realize the spacing is what might be the killer so I'm hoping a 4 speed guy will relate something like:

"The 4 speed is aweful because the gap between 2nd and 3rd is so large I am far awawy from my torque peak when exiting tight corners"

or

"The four speed works okay, you just have to carry speed in the corners so as not to drop too much"

etc.

I posted my ratios and speed in gears some time back, I need to look for that post and maybe folks can comment.

Ron

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Ron
http://www.gt40s.com
Lotus Turbo Esprit
Ford Lightning
RF GT40 Replica
Jensen-Healey: IT prep progressing!

Ron, I'm somewhat of a JH enthusiast and have been reading about your project with a lot of enthusiasm. You are doing what I occasionally thought about. In regards to the transmissions, I've owned 4 different JH and actually prefer the 4 speed on the street. To explain, the 5 speed is a close ratio transmission with 1:1 5th gear which requires more shifting. The 1st gear is also a bit tall, especially with the 5 speed rear end. For that reason, the 5 speed should be ideal for road racing. I've never heard of the Getrag grenading unless one is talking about some serious power such as a supercharged 907. If anything, the UK/Chrysler 4 speeds are known to be weak and the 5 speeds have a good reputation for reliability.

I race a 4 speed ITB Capri with a 4:11 rear end. I pretty much only use 3rd and 4th but it works pretty well since the motor has a wide torque band. With my little 2.0, I pulls past redline (6800rpm) at 2 of the 3 regional tracks so you'd have to run a taller rear end gear with the more powerful 907. I also race an ITA Capri with 3.89 rear end and it actually pulls well over redline (7200rpm at Thunderhill) in 4th.

I also have an ITB GTI with the close ratio 5 speed and run the stock r&p gears. I use 3rd and 4th in that car and have never touched 5th gear. Yes, works great.

Interesting info on the transmissions. I've had about 4 or 5 builders comment on the 5 speed being weak hence the JH kit to swap in the Toyota 5 speed into the cars. You're the first I've known to say anything positive about the unit. I've got both and can use either, but just looking for good opinions. So, your 4 speed is okay in your car?

R

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Ron
http://www.gt40s.com
Lotus Turbo Esprit
Ford Lightning
RF GT40 Replica
Jensen-Healey: IT prep progressing!

[This message has been edited by rlearp (edited October 29, 2004).]

Unfortunately, I have 3 4speeds and they all have problems with 2nd and 3rd gear not staying engaged which is usually caused by a couple of nuts working loose on the shaft keeping the gears together. Typical problem, seems most of the 4speeds need to be gone through. Unfortunately, permanent damage results when this happens. My 5 speed works fine although the effort to shift is a bit high in my opinion. It's not a slick shifting box like the 4speed.

I've never heard of a Getrag 5 speed breaking and even Delta Motors only has good things to say about them other than the shifter bushings. Toyota 5speed is an excellent transmission with O/D which is better suited for most people who want to lower their cruising rpms. It has a great reputation for strength too, so if one is going to the trouble and expense of converting to a 5speed, Toyota is a good way to go. Back to the Getrag, I'd be interested in an example of it grenading due to bad design or weakness. It's a close ratio 5 speed so a benefit as a legal trans for the JH.

There are always rumors floating around, some become "fact" when they are continually repeated. BTW, I keep hearing that Toyo RA1s need to be shaved when used in dry conditions or the tires will chunk. OK, I and many others start 12 and 25 hour enduro races out here in California with brand spanking new Toyo RA1s full tread and I've never seen one of those tires chunk. Does anybody know of an example where a Toyo RA1 full tread tire has chunked?

Totally agree with you on the rumors issue. Ron, I just can't see how the 4 speed would be a better choice than the 5. With a rev happy, peaky motor, you need 3-4-5 to keep the motor where it needs to be.

On the RA-1 issue, I ran full tread RA-1s on my street Lotus Esprit that I have tracked several times. No chunking, even wear and the tire at full tread is a decent street tire (in all be the nastiest of downpours).

Ron,
In my 240z, 3:90 diff, at Road Atlanta I only use 3rd and 4th. Savannah was the same with a 3.73. At CMP, I ran a 3.73 diff and used 2nd, 3rd and 4th. 2nd was way too low, had to shift out rather quickly or hit the rev limiter. I never tried the 3.90 at CMP.
A 3.73 had 2nd too low for turn 7 and 3rd too high. The 3.90 was just about right.

A 4.11 at Road Atlanta can lead to valve spring problems in a legal 240z. But its great in turn 7.

A 4-speed is a simpler rebuild (less moving parts and fewer gears)

The less I have to shift, the less time I lose shifting gears. Just my 2 cents.

Tom

Here are the ratios and speed in gears at max RPM for the two boxes:

4 Speed
Ratios Speed
3.12 42.3
1.99 66.3
1.30 101.9
1.00 131.9

5 Speed
Ratios Speed
3.37 39.2
2.16 61.1
1.58 83.5
1.24 106.3
1.00 131.9

I don't know of any car that I know that has blown up a 5 speed, but, Dave Bean and Judson Manning both advised me to steer clear of the Getrag 5 speed box. That said it won't stop me from using one - I'm fairly well known for not doing what people tell me ;-).

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Ron
http://www.gt40s.com
Lotus Turbo Esprit
Ford Lightning
RF GT40 Replica
Jensen-Healey: IT prep progressing!

[This message has been edited by rlearp (edited October 29, 2004).]

[This message has been edited by rlearp (edited October 29, 2004).]

Ron,
Yes I have the cars confused.
Tranny selection would also depend on the torque curve for that engine, Have any charts or guess for the IT output?
My VIR weekend ended quickly...my front wheel just clipped a spinning IT7, bent frame, firewall, TC rod...I will be in a blue 260z #23 in saturday ECR, stop by.
david spillman

looking at those ratios I can not believe that the torque curve would be wide enough to make the 4 speed a good choice on any track where you need to use 2nd. the gap is pretty big.
can the tranny be swapped out withthe mtor in the car? if so you may want to swap between tracks, but i would start with a rebuilt 5 speed.
dick

Yep I am afraid of that gap too...5 speed will have to be used, Ron

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Ron
http://www.gt40s.com
Lotus Turbo Esprit
Ford Lightning
RF GT40 Replica
Jensen-Healey: IT prep progressing!

Damn David, I'm sorry to hear that. I saw you on the entry list and then didn't see you on track. Was hoping to see that Z hang the tail out in 4....

How bad is the damage? Can you get it fixed for the ARRC?

Quote:

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Originally posted by JeffYoung:
Damn David, I'm sorry to hear that.
How bad is the damage? Can you get it fixed for the ARRC?

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Yep, I plan on being there
The car is real close to being straight...a log chain, tree, tractor, and duramax diesel..pulled her right out. Hope to get all four corners pointed in the same general direction by Thursday....

Dave,
Which corner did you hit it on? If you need some spare parts, PM me on CZC under the same username.
I've still got some of the OEM RH frame rails left.