Disassembled gearbox --- What I found

3literpwr · 10-14-2019, 03:25 AM

Bought this SC back in 2013 to build into a Group 2 rally car for the Rally America series, but after a series of head stud failures and then starting at a start up called Rivian, the project sat for years. Now i'm reviving the project and getting the body moved along and was digging into the trans. I have three gears to install that will make the box similar to the SCRS gearbox and move 4th to 5th. Again, the car is being build for gravel and wont ever see speeds over 120mph. Tore into the box which was "rebuilt" by Vertex just a couple K before I bought the car. First inspection is that the dog teeth look good, but the larger center bearing race was loose. Also, this tiny pin seemed to fall out, so that's not ideal I assume.

Who's needed to do the bearing mod and what options are out there? I see that Wevo and CMS both offer options.

faapgar · 10-14-2019, 03:31 AM

Tiny pin is for the reverse switch.Fred

john walker's workshop · 10-14-2019, 03:35 AM

It falls into the depths if you remove the end cover before removing the backup switch and pin.

stownsen914 · 10-14-2019, 05:04 AM

In the third picture from the top, the dog teeth on the right look funny. Doesn’t look like wear, but who knows. Is that a special synchro hub?

Driven97 · 09:52 AM

Quote:

Originally Posted by stownsen914

In the third picture from the top, the dog teeth on the right look funny. Doesn’t look like wear, but who knows. Is that a special synchro hub?

1st gear teeth are asymmetric, no?

gomezoneill · gomezoneill's Garage

The best mod for the bearing is to have a machine shop cnc the hole to a larger size and press in a steel sleeve. I had mine done at a local machine shop and they knurled the case and pressed in the bearing and it's held up just fine.

Joe Bob · Joe Bob's Garage

Quote:

Originally Posted by gomezoneill

The best mod for the bearing is to have a machine shop cnc the hole to a larger size and press in a steel sleeve. I had mine done at a local machine shop and they knurled the case and pressed in the bearing and it's held up just fine.

Aase brothers did mine and I installed a WEVO support plate.

Jon B · 10-14-2019, 07:33 AM

Quote:

Originally Posted by 3literpwr

I have three gears to install that will make the box similar to the SCRS gearbox and move 4th to 5th.

You cannot move 4th to 5th, if you meant that literally.

3literpwr · 10-14-2019, 08:56 AM

Well, I did think you could (4th to 5th) as I thought a gbox man told me that if thats not that case, i'll just find myself something that's close to 1:1.

Thanks for the insight.

3literpwr · 10-14-2019, 11:09 AM

I was mistaken, I'm moving 3rd to 4th and bought a new 2nd, 3rd and the 1:1 5th. It's been a couple years since I bought all the parts, so this escaped my memory.

Matt Monson · 10-14-2019, 11:13 AM

Quote:

Originally Posted by Driven97

1st gear teeth are asymmetric, no?

Correct.

3literpwr · 10-14-2019, 11:19 AM

Here are the ratios.

Driven97 · 10-14-2019, 11:24 AM

Ooof I want that 2nd gear on that diameter tire.

stownsen914 · 10-14-2019, 03:02 PM

Quote:

Originally Posted by Driven97

1st gear teeth are asymmetric, no?

Apparently I was remembering 901 synchros.

dwelle · 10-14-2019, 04:28 PM

wow, tall tires. what are you running?...

3literpwr · 01:40 AM

I’ll be running a 195/65r15 gravel tire...this and the 205/65r15 are the most common 15" rally tires. Actual height is 25.2”.

MBEngineering · 06:49 AM

HI 3literpwr

will you be using the STD input shaft in the box, or the 954 type with the 2nd cut on the shaft, as you will be running mainly on the loose, there is a good chance it will not last,

if you have the chance to change the box, I would run one of GT's 8:35 CWP and more reliable taller gears, or a Drenth input shaft with the 1st and 2nd cut on the shaft

also a oil spray bar system if a full under guard, engine and box is used, subject to Reg's

3literpwr · 10-15-2019, 05:16 AM

MBEngineering - Not planned to use the 954 part as of now as i've been trying to balance budget and performance. Seeing as that's a 954 part, I can only assume that it's rather pricey and frankly, this car will see limited use. I ran in the Rally America series though the mid 2000's and loved the sport, but spent all my time and money going racing. This time around, I wanted to build something fun and only do the events local to me. SnoDrift (winter) and Lake Superior are both held in Michigan and 8 months apart and would hit on these goals.

MBEngineering · 10-15-2019, 06:25 AM

HI 3literpwr

if the budget will alow, I would put a GT 8:35 CWP in and gear it round that, as a larger 2Nd gear, fixed gear on the input shaft will last longer and have less chance of braking in 1/2, /loosing a tooth

the rally boxs I have worked on over hear with 3Lt engines and off road use, has had 2nd gear prob's with a 8:31 CWP, changing to a 8:35 and a larger/taller 2nd stopped the prob', the 16 tooth 2nd gear dos'e have a tendancy to fail when subject to loose road surface and a torquey engine, when having no grip and then grip

the 954 ratios ran ;

8:31 CWP, 1st 11:35, 2nd 15:30, 3rd 21:29, 4th 25:27, 5th 27:24

also with options;

CWP 8:31, 8:35, 7:33

1st/2nd 11:35/16/35 (both on the same shaft), 3rd 20:32, 4th 23:29, 5th 26:26

would seem a shame that you have spent time and $$$ getting the car ready for the 2 events and at some time in 1 of the events the box lets go, when you have the chance to sort it out now, just my thoughts

kevingross · 10-15-2019, 08:29 AM

California Motorsports for the loose bearing outer race. Check both races, in both the diff carrier and gear carrier. CMS does all mine needing this repair, excellent work.