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Discussion Starter #1
I'm thinking about going with a Jerico 4 speed trans with side shifter from Hightower Racing in South Carolina for my FFR spec racerwhich is only road raced. The tranny comes with a 26 spline input and 31 spline output shaft and will bolt up to my existing bell housing. I was wondering if anyone had installed one of these in their cars and, if so, were there any fitment issues. My concern is that I may have to alter the trans tunnel sheet metal to make room for the shifter right where the seat is and there's hardly any room there to bump it out.
I would be interested to hear about any issues that arose. Thanks in advance, Bob
 

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I doubt you will have a problem. I have a G-force 5R box with left side control links and it fits fine. I had to cut and relocate a top diagonal bar, that's it.

http://www.gforcetransmissions.com/shifter_5_hn1000.asp

Same as the picture but I have a made shift linkage to move the shifter forward. That is one of the main differences, the shifter is really far back - almost behind the seat
 

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Discussion Starter #3
I have heard the Long shifter is more compact (does not stick out as far) than the Hightower . I may just get the jerico and purchase the Long shifter separately. They can locate the shifter 19" back from the face of the tranny which will put it back to the original T5 location. I may also fabricate a new shifter mounting bracket in an attempt to move it up 3 inches which will require shorter rails.
How do you like your 5R? How is it holding up?
 

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I really like it. It's much easier to race with the left foot braking and right foot throttle. You can overlap the two pedals and make the car maneuver better. Also, shifts are much quicker and less loss of speed. It took two full days to get the hang of driving this type of trans. The downshift speeds have to be matched well or its makes some ugly sounds. I let the throttle off for a split second on upshifts. The Gforce guys said it would last 10xs longer between rebuilds. It was one of the best improvements I have made so far.
I made a linkage to bring the shifter up to a "normal" front hand position. It is really required since the shifts have to be hard and positive. Its not like clicking a syncro box. More like slamming gears.
 

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Discussion Starter #5
Glad you like your trans. I've been through 3 stock transmissions in the last 6 years so I need to step up and get one made for racing. I plan on ordering my Jerico this week after deciding on ratios.
I run with a bunch of guys (SCCA) that have 800 -900 hp Cup cars and they all use Jericos. One of the guys tried Jerico's 5 speed road race trans but didn't like it and went back to the old 4 speed. The 5 speed has a clam shell casing but no pins, just bolts. Pushing a 3300 pound car with 800-900 hp caused the housing to flex. These guys have money so they switch out rear ends and transmissions for the various tracks. Must be nice! I'll have to pick my ratios carefully so I don't run out of gear on the longer tracks.
 

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I wrote a program years ago to pick gear ratios and probably won’t run on modern computers. I will see if I can update it. You pick first and forth gears speeds and the program does the rest.

E-mail me your e-mail address and I will see what I can do.

Bill Lomenick
[email protected]
 

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Here are my ratios. They worked well with 3:27 rear. Topped out at 152. I later switched to 3:08s and hit the 161 at VIR, but didn't like the new 3rd and 4th ratio. Didn't work well at Summit and I felt it was a little sluggish.

3:27
3.022/50
1.724/88
1.383/110
1.154/132
1.000/152

3:08
54/94/117/140/161
 

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Discussion Starter #8
Bill, thanks for the offer but I have never ran a speedometer or used any on board data so I don't know the speeds I reach or need to reach. I have a 3.08 rear gear and a .82 fifth which left me with a lot more gear at Summit Point but I was just about right on the long back stretch at VIR (5800-6000 RPM).
My peak torque is at 5200 RPM and my peak hp is at 6300 RPM. The tranny I'm interested in is only a 4 speed with a 1.00 so iI would have to go with a 2.?? for the back stretch at VIR as I'm running a 24.78" diameter rear tire. Jerico says they may be able to build a Pocono box with a .9??? 4th gear so I may be able to keep my 3.08. I'll have to wait until I hear from Jerico before I decide.
I do appreciate all the input as it helps me with my decision. Thanks, Bob
 

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I worked up a spreadsheet that you can enter all your variables including the Jerico’s main drive ratio and it gives you high and low speeds along with RPM drop when shifting and speed gained in each gear. It will work for 4 or 5 speeds. It doesn’t do as much as my original program because it doesn’t choose the ratios from a gear chart. But with a gear chart it is easy to make informed decisions. What I shoot for in choosing ratios is to gain about the same MPH in each gear. So if I know what the slowest speed and the highest speed will be and the lowest and highest RPM are going to be it is easy to choose a first gear that will stay above the minimum RPM at the slowest part of the track and choose a top gear that will stay below the highest RPM in your case 4th gear. I then subtract the top speed in first gear from the top speed in forth gear and divide by 3 which gives the MPH you want to gain in each gear. So if you have a top speed in first gear of 50 MPH and 150 in forth gear you have 150-50=100 then 100/3=33 MPH gain in each gear. Then it is a matter of choosing ratios that will give you a top speed of 50, 83, 116, 150. This may not perfect for all tracks but from my experience comes very close. The only time I had to vary from the chosen ratios was for Willow Springs going up the hill to turn 4 where I changed second gear one tooth so that I wouldn’t have to shift before reaching the top. This may not be mathematically correct because it doesn’t take into account the engine torque curve but it is easy to use and works.

Bill Lomenick
 

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Discussion Starter #11
Bill, probably the slowest corner I will encounter will be about 37 MPH and the fastest I can see me going is 150-155 mph (on a good day). I would like to keep the high RPM to 6700 but I have no idea what my low rpm's would be. I am stuck with a 4th gear ratio (4 speed) of 1.0 and I'll probably have to go back to the 2.73 rear gear as that is the next one down from 3.08. With the 3.08 and a 1.0 I would run out of gear on the longer straights.
Can you work with these numbers on your spreadsheet. I am running a 24.78 diameter tire. Thanks, Bob
 

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no cooler. I use redline shockproof lightweight oil, thats it.
 

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TOP ENGINE SPEED 6700

INPUT SHAFT 24

CLUSTER SHAFT 25

RING AND PIN 3.08
Engine RPM
Final Drive Ratio 3.2083 immediately after
Redline Shift in
Gearbox Ratios- LOW SPEED- Top Speed- Previous Gear RPM Drop--- MPH Gain
1st-----2.361-----------38.9----65.2-------N/A-------------N/A------------65.2
2nd-----1.51------------60.9----102.0------4,285-----------2415-----------36.7
3rd-----1.178-----------78.0----130.7------5,227-----------1473-----------28.7
4th-----1---------------91.9----153.9------5,688-----------1012-----------23.3


LOW ENGINE SPEED 4000

I can’t get the columns to line up they should be closed enough to see what is happening. I will work on the data for 2.73 ring and pin and see if I can’t get it better. If you would like a copy of the spreadsheet or talk about it I can be reached at:

[email protected]
818.717.5694

Bill Lomenick
 

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Discussion Starter #15
Bill, first thanks for working this for me. After reading your post a few times I finally realized what you were doing and printed a copy of Jerico's ratios and with a calculator in hand started off. It's amazing how close both of us were.
With a 3.08 rear gear my trans ratios came out to 2.36, 1.45, 1.17 and 1.0. Only second gear was different because I needed a little more higher speed for one of the turns so I could carry that gear through the turn.
I would like to see what you come up with for the 2.73! I know with the 3.08 I will not make sound at Summit unless I do some muffler work (105 -107db).
I was looking at your picture and it looks like an older sports racer but the wing throws me off. What is it?
 

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TOP ENGINE SPEED 6700

INPUT SHAFT 22

CLUSTER SHAFT 26

RING AND PIN 2.73
----------------------------------------------------Engine RPM
Final Drive Ratio 3.226363636-----------------immediately after
-----------------------------------------------------Redline Shift in
Gearbox Ratios-----LOW SPEED--Top Speed--Previous Gear---RPM Drop---MPH Gain
1st 2.679-----------34.1------------57.1------------N/A------------------N/A--------57.1
2nd 1.655-----------55.2------------92.5------------4,139----------------2561-------35.4
3rd 1.231-----------74.2------------124.4-----------4,984----------------1716-------31.9
4th 1---------------91.4------------153.1-----------5,443----------------1257-------28.7

LOW ENGINE SPEED 4000

This is for the 2.73 ring and pin and 34.78 dia tires. I need to redo the 3.08 because I used the wrong tire dia.

The car is the last DSR I designed and built. It had a Suzuki GSX-R1000 engine putting out around 200 HP and the car weighed about
850 pounds. It wasn't all that fast but it was quick. With all the ground effects it that a top speed of about 145 but could turn
laps at Willow Springs in the 1:16's. This car and several others I made set lap records some of which still stand.

I will get the corrected 3.08 data ASAP.

Bill Lomenick
 

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TOP ENGINE SPEED 6500

INPUT SHAFT 24

CLUSTER SHAFT 24

RING AND PIN 3.08
---------------------------------------------------------Engine RPM
Final Drive Ratio 3.08---------------------------------immediately after
---------------------------------------------------------Redline Shift in
Gearbox Ratios----LOW SPEED------Top Speed----Previous Gear---RPM Drop----MPH Gain
1st 2.237------------37.4-----------69.5---------N/A------------------N/A---------69.5
2nd 1.45-------------57.8-----------107.3--------4,213----------------2287--------37.7
3rd 1.182------------70.9-----------131.6--------5,299----------------1201--------24.3
4th 1-----------------83.8-----------155.6--------5,499----------------1001--------24.0

LOW ENGINE SPEED 3500

This is the corrected 3.08 data.

I started by choosing a main drive set that gets the top speed you want then pic a first gear that works for your minimum speed and then try to pick gears that give about even MPH gains. If a choice need to be made on the splits I select a larger MPH gain in the lower gears because they have more mechanical advantage.

I also looked at using the 24/25 main drive set and the 1-2 shift had a very large drop in RPM and the 3-4 was a very small drop which I don’t think it would work very well.

Good Luck

Bill Lomenick
 

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Discussion Starter #18
Thanks for all the work Bill. I will go with those ratios but use 1.632 for second as I need a tad more gear for one of the turns. It's still on the 26/22 main drive so it will work.
So are you still racing the DSR? It's classed as a P1 or P2 now in SCCA. I'm also a licensed SCCA flagger and worked the Runoffs a few weeks ago at Laguna Seca. I always enjoy watching the prototypes as they carry so much speed through the corners. Of all the run groups the prototypes had problems with fires, with 5 or 6 catching fire over the 6 day event. Although I enjoy the prototypes my heart is with GT1, AS and T1. Listening to them race is like listening to a classic rock song, you never tire from it.
I'll let you know how the tranny works when I get it in and on the track. Bob
 
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