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MrDangerUS

Citroen 9 x 35 Pinion / Crown wheel

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Regular Citroen box CWP ratio on our cars is 8 x 35 (4.375:1).

 

I would like to try 9/35  (3.888:1) CWP to make the OE gears "taller".

What cars are they used on?

I heard that some version of Citroen C35 Van and/or BX 4TC had it in their trannys.

 

Any pointers?

Edited by MrDangerUS

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Upgrade today to remove Google ads and support TLF.

Perhaps Harry may chime in, if he even is aware about this ratio?

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Originally, Citroen C35 gearbox was designed to run in the opposite direction on Citroen DS and SM

and therefore

the Crown Wheel and Pinion teeth profile is "backwards" for the Lotus/Maserati mid-engine configuration!

 

The teeth on gear sets have both a drive side and a coast side. Usually the pinion should rotate the crown wheel on the drive side of the tooth. If however the pinion rotates the crown wheel on the coast side, strength of the gear set can be reduced by as much as 20%.

Hard to believe, but this happened "by design"! Typical "cost avoidance" policy.
Lotus CWP is weak in forward drive; its strength is better in overrun!
Have a look on Google for the driven and coast sides of the gear and the slope differences.

Similar situation exists on the front Land Rover differential.
In the front axle of a Land Rover, the gear set is running “backwards”, being driven on the coast side of the teeth rather than the driven side and as such is weaker. Reverse cut gears are required in this configuration!

There are only a few Specialty Gear companies which have produced reverse rotation gear sets to allow the gears to be driven in the correct way. This also allows the pinion to transfer the load forces into the bigger pinion head bearing rather than the smaller tail bearing, such increasing the life of the bearings.

The only SOLUTION would be to make a NEW SET (crown wheel/pinion pair) featuring reverse-cut gears!

I have been quoted $1800-$2000 per set.

I'm sure I could negotiate a better price with more orders/sets.

 

???
I'm wondering, how many Citroen equipped car owners would sign up for the "group buy" of the Crown Wheel/Pinion shaft pair with:
- more favorable final drive ratio** of 9/35 (3.888:1)
- teeth profile corrected for "reverse" rotation
- beefed up dimensionally
- Cryo (and RMS ) treated

** 3.888 ratio would provide the OE box with better gear spacing, see attachment.

Check file at post #47 here 

http://www.lotustalk.com/forums/f164/citroen-transmission-questions-181522/index3.html#post4085186

 

 

 

HOW MANY OWNERS WOULD GO FOR IT?

PLEASE CHIME IN!

 

 

 

P.S.
Also have a look at the Citroen box oil flow when the box is rotating in the intended direction, notice the drain going into the 5th gear extension.
Now, notice what happens when the lower gear clusters are going the “wrong” way!
And imagine that.... Lotus has 5th gear oil problems!

LOL

Edited by MrDangerUS

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I did some homework on this and found out that 9/35 is not the best when it comes to strength. If you want to read more about this development, please Google:   Citroën g/box Crown Wheel and Pinion  

New Citroen crown gear and pinion re-design is almost completed. Blueprints will be finalized in a couple of weeks. 
Then, I'll start competitive quoting of the new design.
With Cryogenic treatment, this CWP should be able to sustain 380Nm.
I hope, this will open new horizons to all owners of Esprits with Citroen transmissions.

What is the next weak link, you may ask... Well, how about the clutch cover and the disk?

Edited by MrDangerUS

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all cwp sets with different ratios back in stock.  4.85, 4,37 and 3.88. 

Brand new or very, very good used.

 

 

cheers,

 

Harry Martens

IMG_3317.jpg

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Hi John

 

Would you keep me updated on this development please

 

Steve

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i may be interested in this. having the trans moving in the correct direction is a good idea.

but i think i would like to keep the stock ratio. i like the way the car is geared. with your ratio  we will be loosing acceleration.

would they make one with the stock ratio also?   and who are you having make them?

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hello

Just discover that a 7x34 is possible for a Lotus Esprit. I thought it was not possible. What is the best advantage to use it. As far I remember some of Citroën DS Car have been sold in the USA with this ratio. 

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2 hours ago, catesprit said:

hello

Just discover that a 7x34 is possible for a Lotus Esprit. I thought it was not possible. What is the best advantage to use it. As far I remember some of Citroën DS Car have been sold in the USA with this ratio. 

Hi, yes also in stock. All 3 different ratios cwp in stock, 7/34, 8/35 and 9/35.

 

cheers,

 

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ok thanks for the information but what is the advantage to use this ratio? and also what is the cost?

Hugues

 

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Hi, advantage is faster acceleration and stronger cwp. ( thicker teeth ) Very good used Set costs 1300 euro.

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ok  and very good for stronger cwp but to keep the same max speed it is necessary to change the 5th pear pinion to get something like 38x26 if I don't do a mistake! and 26 teeth pinion doesn't exist and seems to be no good idea to get a 1.46 ratio for a 5th gear and may obliged to change also the ratio for the 4th gear; But I am not a specialist, just wondering what is the best to do because i have to change the cwp.

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Hi, I do have a 5th gear set 1.53 ratio. Step from 4 to 5 is a little bigger. Not possible to change ratio for 4th gear. On secondary shaft 3rd and 4th are gear train.

 

cheers,

 

 

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thanks for all

how do you get a 1.53 ratio if you keep the 38 teeth pinion? 38x25 gives 1.52 ratio.  you are right to say  that with this ratio there is quite a big step between 4 and 5 th gear. Have you been told about a 6 gears C35 gearbox?

I like the idea of stronger cwp, faster accelaration but I don't want to low the max speed and to have hudge fuel consumption;

What is the solution?

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Hi, six speed is no option. Way to expencive. I modifiy the Citroen C35 Diesel 5th gear set. Wich is 40/26 but has different splines on secundairy shaft.

 

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