3.73 Ring & Pinion gears for FD's
09-13-07, 04:46 PM
#1
Full Member
Thread Starter
3.73 Ring & Pinion gears for FD's
After a lot of research on the subject,
The search for longer gears for the FD Differantial carrier, has finally come to an end.
We have a direct replacement solution for those who are looking for taller gears for their FD's without having to resort ot the Cobra 8.8 IRS carrier and subframe option.
Bellow are pictures of 3.73 Ring and Pinion gear that will dirrectly interchange into the differential of the FD Rx7
The 3.73 is on the left, the OEM 4.10 is on the right
This gear came out of an '89 MPV Sport (5 speed version)
We have located the OEM P/n and are in process of acquiring global availability info.
The ONLY difference between the 2 gears is the main bearing collar (The machined surface for the big Pinion bearing) on the 3.73 gear shaft is 5mm smaller on the OD.
Due to the increased mechanical loads of the Turbo engine on the FD.
The main Pinion bearing is bustantially larger, but the shaft that transmits the power is exactly the same in all other dimentions on both gears.
I found a solution to accomodate the larger OEM Pinion bearing of the FD to the narrower collar found on the 3.73 shaft.
We were able to source and acquire some hardened sleeves to take up the difference between the OD's and ID's or each.
Below, I will post some pics illustrating differences and the applied solution.
GT1-20b
The search for longer gears for the FD Differantial carrier, has finally come to an end.
We have a direct replacement solution for those who are looking for taller gears for their FD's without having to resort ot the Cobra 8.8 IRS carrier and subframe option.
Bellow are pictures of 3.73 Ring and Pinion gear that will dirrectly interchange into the differential of the FD Rx7
The 3.73 is on the left, the OEM 4.10 is on the right
This gear came out of an '89 MPV Sport (5 speed version)
We have located the OEM P/n and are in process of acquiring global availability info.
The ONLY difference between the 2 gears is the main bearing collar (The machined surface for the big Pinion bearing) on the 3.73 gear shaft is 5mm smaller on the OD.
Due to the increased mechanical loads of the Turbo engine on the FD.
The main Pinion bearing is bustantially larger, but the shaft that transmits the power is exactly the same in all other dimentions on both gears.
I found a solution to accomodate the larger OEM Pinion bearing of the FD to the narrower collar found on the 3.73 shaft.
We were able to source and acquire some hardened sleeves to take up the difference between the OD's and ID's or each.
Below, I will post some pics illustrating differences and the applied solution.
GT1-20b
09-13-07, 05:55 PM
#5
Full Member
Thread Starter
This last pic., illustrates the Large FD pinion bearing, seated over the hardened collar ready to be pressed over and onto the shaft permanently.
Obiously, a NEW crush collar " Distance piece" as Mazda calls, needs to be installed in order to maintain correct spacing
The crush collars are a one time use only part, as the name implies, it crushes and compresses to a specific distance and presure, maintaining both pinion bearings firmly agaist their respective races.
The the driveshaft's drive plate and the Pinion nut are then slipped over the splines and torqued to OEM specs.
We are activelly working w/ the manufacturer to see about finding sone new gears for resale.
We are keeping hardened collars in stock for anyone interested in doing this conversion.
Also, If You find a used gear, we can set it up for you for a nominal cost in addition to installing all the new bearings, shims and seals.
Carlos
CLR Motorsports Inc.
GT1-20b
PS.
Especial thanks to "Ray" from the V8's Rx7 Forum.
Who's help and collaboration helped bring this project to fruition.
'c
Obiously, a NEW crush collar " Distance piece" as Mazda calls, needs to be installed in order to maintain correct spacing
The crush collars are a one time use only part, as the name implies, it crushes and compresses to a specific distance and presure, maintaining both pinion bearings firmly agaist their respective races.
The the driveshaft's drive plate and the Pinion nut are then slipped over the splines and torqued to OEM specs.
We are activelly working w/ the manufacturer to see about finding sone new gears for resale.
We are keeping hardened collars in stock for anyone interested in doing this conversion.
Also, If You find a used gear, we can set it up for you for a nominal cost in addition to installing all the new bearings, shims and seals.
Carlos
CLR Motorsports Inc.
GT1-20b
PS.
Especial thanks to "Ray" from the V8's Rx7 Forum.
Who's help and collaboration helped bring this project to fruition.
'c
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09-21-07, 09:32 AM
#10
Ls6 FD
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Awesome. I'm definitely interested in this. Where can we buy the stuff and how much?
What sort of power levels have you tested this at? It seems like it wouldn't be as strong as the FD rear. Although it has a hardened collar pressed over it, that doesn't seem like it would help the twisting motion?
What sort of power levels have you tested this at? It seems like it wouldn't be as strong as the FD rear. Although it has a hardened collar pressed over it, that doesn't seem like it would help the twisting motion?
10-21-07, 01:39 PM
#16
Full Member
Thread Starter
Unfortunetly, this will not work for the 2 gen.
10-21-07, 02:00 PM
#17
Full Member
Thread Starter
I've successefully set up the 3.73 Ring & Pinion gear inside my FD's diff.
I opted to use an LSD. from an FC rather than the FD's Torsen unit.
The Torsen is not as compliant when driven on un-even pavement specially when putting down big power.
Pic's will follow early next week.
10-21-07, 03:03 PM
#18
Full Member
Thread Starter
Ernie,
The more power You make,
The longer the gear You can pull or stretch.
Shortening the gear like going fron a 4.10 to a 4.30 gains mechanical advantage, or leverage for the engine to do the work easier.
Certainly, a great way to increase rate of acceleration, but at the expence of top speed.
Increasing engine's power output reduces the need for shorter gears.
The engine is capable of doing more work (accelerate) without sacrificing speed or fuel consumption.
Combine a good 6 speed gearbox: One having a good low 1st gear, proper gear drops, a decent OD, somewhere in the 20% range (.80). Along with a longer rear end gear, and ...
You get the best of all worlds: Hard acceleration, great top end, and better milage !
