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91 Hatch rally car
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Discussion Starter · #1 · (Edited)
SI large bearing box in our rally car.

We chucked in the full MFactory close ratio set (new 1st, OEM 2nd, new 3rd, 3rd turned into 4th, new 5th) with a full rebuild kit. Everything but 5th is working great. Shifts smooth, runs quiet, ratios are super for what we do.

Here's the issue. 5th howls like crazy and is getting worse. Half of the 5th gear pair is part of the input shaft, so the gear kit came with only a new intermediate shaft gear. We put it all back together using all the gears that came with the kit. Clearances were set to oem specs using a dial indicator and the FSM for how to do it.

I'm the first to say that I'm not a pro at rebuilding transmissions, but I've been in more than a few with pretty good success. Did I miss something? Was there a new input shaft I needed to get? The other gear pairs are quiet (for straight cut gears). I want to use the shorter 5th, but not if it's going to grenade.
Hopefully smarter people can help me here.

Added for your interest. We just got back from Rocky Mountain Rally in Cochrane Alberta. https://rockymountainrally.com/
P3 in class, 5 seconds behind P2. We got cock blocked by a bunch of cows on the 4th stage that cost us a new pair of undies and probably 20 seconds.
 

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93 Civic HB SI
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SI large bearing box in our rally car.

We chucked in the full MFactory close ratio set (new 1st, OEM 2nd, new 3rd, 3rd turned into 4th, new 5th) with a full rebuild kit. Everything but 5th is working great. Shifts smooth, runs quiet, ratios are super for what we do.

Here's the issue. 5th howls like crazy and is getting worse. Half of the 5th gear pair is part of the input shaft, so the gear kit came with only a new intermediate shaft gear. We put it all back together using all the gears that came with the kit. Clearances were set to oem specs using a dial indicator and the FSM for how to do it.

I'm the first to say that I'm not a pro at rebuilding transmissions, but I've been in more than a few with pretty good success. Did I miss something? Was there a new input shaft I needed to get? The other gear pairs are quiet (for straight cut gears). I want to use the shorter 5th, but not if it's going to grenade.
Hopefully smarter people can help me here.

Added for your interest. We just got back from Rocky Mountain Rally in Cochrane Alberta. https://rockymountainrally.com/
P3 in class, 5 seconds behind P2. We got cock blocked by a bunch of cows on the 4th stage that cost us a new pair of undies and probably 20 seconds.
Those damn cock blocking cows hahaha
 

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Brokedick Millionaire
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Surprise you even got the transmission to spin. New 5th gear set rubs on the case. Bense was test fitting one of the early Gear-X sets and had this happen. Because of his pics I was able to see the marks on the outer case.

Took me a while to figure out WITFF where you talking about, only replacing 1/2 of 5th gear, it comes as a complete pair. I believe you are talking about 1st gear where just the CS (big gear!) gets replaced.
 

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91 Hatch rally car
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Discussion Starter · #6 ·
Surprise you even got the transmission to spin. New 5th gear set rubs on the case. Bense was test fitting one of the early Gear-X sets and had this happen. Because of his pics I was able to see the marks on the outer case.

Took me a while to figure out WITFF where you talking about, only replacing 1/2 of 5th gear, it comes as a complete pair. I believe you are talking about 1st gear where just the CS (big gear!) gets replaced.
You, sir, are absolutely correct, as usual. I was doing this from memory after a long weekend. I was thinking last might about the 1 gear thing and realized that the shaft had a small gear formed into it, making it 1st, not 5th. I was on my way to fix the post when I saw you responded.
What's the fix? Assuming there's enough meat there, relieve the case?
 

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Discussion Starter · #8 ·
Yep, takes longer to clean the alum. debris out of the case than it takes to do the clearancing.
Cool. I can do that. When we did the gears, we were short on time. We got it back together, winched it on a trailer, got to the start line and sent it hard. There probably was some case clearancing done there. I'll look for those grooves and start there.
 

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Discussion Starter · #10 ·
If it has cleared itself, drain the oil and refill, plan on a teardown to clean it out in the off season,

My customers season is over for the year.

PICS!!!!!
The box is going to get opened up probably this weekend. My co-driver and I were talking about this last night. We're probably going to go back to the OEM 5th gear pair. In rally, there are transits between stages that can be 30-40 miles that we get to do multiple times an event. The shorter 5th gear makes 60 mph at 4500 rpm on the road for that long painful. Additionally, there's only about an 11mph difference between 4th and 5th at 7500 (103 to 114). We'd rather give up a bit of top speed that we will never notice and gain a much more comfortable transit. If it doesn't work out, I can always throw the shorter 5th pair back in. If there's anything interesting in the case when I open it up, I'll post pics.
 

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Discussion Starter · #11 ·
interesting that rpm force is it different comparing to what it was before ?
I'm not sure of your question. All other things being equal, speed at a given rpm is determined by gear ratio. The MFactory 5th is 1:1. The OEM 5th is more like .83:1. This means that the OEM 5th will give you a higher top speed at a given rpm, or more importantly, a lower rpm at a given speed.

Did I answer you question?
 

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BATSLOMAN GIVES NO FUCKS.
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I'm not sure of your question. All other things being equal, speed at a given rpm is determined by gear ratio. The MFactory 5th is 1:1. The OEM 5th is more like .83:1. This means that the OEM 5th will give you a higher top speed at a given rpm, or more importantly, a lower rpm at a given speed.

Did I answer you question?
spammer is gone lol.
 

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BATSLOMAN GIVES NO FUCKS.
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if Im not mistaken, there is another noob with a similar name that joined up a few days ago, that was the first 0_o......the second was when I checked his ip lol
 
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Discussion Starter · #16 ·
If it has cleared itself, drain the oil and refill, plan on a teardown to clean it out in the off season,

My customers season is over for the year.

PICS!!!!!
I looked all over and think we trashed the oem gears that were replaced by the Mfactory stuff. Do you have an OEM 5th pair paying around that I could get?
 
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