What parts are most important when rebuilding my transmission?

[96bmwm3]

I'm thinking of having someone local do my transmission rebuild (just can't stomach the $1000+ for a Shep or TRE rebuild). If I have a stock rebuild performed and replace 2nd gear with a new 2nd gear kit that includes double synchros from Team Rip, is there anything else that is a weak point in these 1G trannys that I should replace?

Currently I'm having trouble getting the car to engage in 2nd gear.

Local shop says they'll do the rebuild for $250 + parts. 2nd gear double synchro kit from TRE is $315. Assuming nothing else major is wrong, I can handle a ~$575 rebuild.

What do you all think?

For reference: http://www.teamrip.com/GENUINE_FACTORY_AWD_PARTS.html

 

[FastGS-T]

The whole reason my car is down right now is because of the tranny. Watch out for launching it hard because it tore my diff into pieces. So maybe upgrade your diff pin or something so you won't destroy everything first few runs at the track.

-dustin

 

[96bmwm3]

What is the diff pin exactly? I'm assuming this is in the differential and not the tranny??

 

[11sec_GSX]

The center differential is the weakest part in a DSM transmission. If you plan on launching the car at the dragstrip or even on the street for that matter, you will want to either weld or upgrade your center diff. Most guys don't recommend the cheapest option of welding the center diff though, if the car is daily driven...But a 4-spider upgrade is pretty expensive and would probably put you over the $1,000 mark with the other work you plan to have done. I have a welded center but my car is by no means daily driven. I would recommend the 4-spider upgrade if you are daily driven. If you are going to go with the cheaper option, I would research a welded center before you do it so you know what to expect. Good luck.

 

[TSIfreek]

When you are rebuilding a trans like ours 2 parts just dont get replaced. It is well worth the money to have shep or tre do it. Its a diffrent expereance shifting one of these tranys when it accually goes into gear you almost have to relearn how to do it. Theres really not the most important parts they all work together or it doent work. Each part has its own job.

 

[turbo90gsx]

Personaly I would say save some more money and just have Shep or TRE build it for you. Its well worth the money and they KNOW what they are doing. I plan on running a full stage 4 from Shep here soon with a welded center diff and locking sleve. This car is my daily driver but im not really too concered as long as it holds the power that I will put down. I already have no power steering, no a/c, no IAC motor, and no FAIV so how bad could a welded center diff be?

 

[TSIfreek]

You dont want a welded diff on the street you start breaking things. Diff axles and rear end hate it unless your going straight.

 

[turbo90gsx]

I was wondering about that, however a welded diff seems to be the best way to get a 50-50 torque split between the front and the rear. A 4 spider center diff will not fully lock up under load will it? The other alternative/additive that I know of is using a viscous coupling locking sleve in place of the visous coupling itself. Are there other ways of locking front and rear power distribution?

 

[turbo90gsx]

I did some more researching on welded center diffs and found this tech article on here.

"Here's why cars with a welded Center Diff has "tire skipping":

The welded Center Diff effectively locks the front and rear shafts together but you still have a rear LSD that allows one side to turn free of the other, to a point. The rear LSD requires a certain amount of torque difference to cause it to differentiate. If it takes LESS torque to break the tire loose then the tire will "skip." My '91 GSX with Welded Diff and street tires chirps on slow sharp turns. Slap on my sticky track tires and no tire slip at all. Why? Because it takes more torque to skip the sticky track tire than it does to differentiate the LSD. That's also why it only does this at slow speeds and not while highway driving. It is not hurting anything or over-stressing the axles."

So other than the occasional tire skipping in inner city driving, it seems like a welded center diff is a good cheap way to lock the front and rear and eliminate another weak part ehy?

 

[raped]

I did some more researching on welded center diffs and found this tech article on here.

"Here's why cars with a welded Center Diff has "tire skipping":

The welded Center Diff effectively locks the front and rear shafts together but you still have a rear LSD that allows one side to turn free of the other, to a point. The rear LSD requires a certain amount of torque difference to cause it to differentiate. If it takes LESS torque to break the tire loose then the tire will "skip." My '91 GSX with Welded Diff and street tires chirps on slow sharp turns. Slap on my sticky track tires and no tire slip at all. Why? Because it takes more torque to skip the sticky track tire than it does to differentiate the LSD. That's also why it only does this at slow speeds and not while highway driving. It is not hurting anything or over-stressing the axles."

this statement is wrong

 

[TRBOBLU]

Welded diffs are a good option unless you have a 3 bolt rear. I had a 20 minute conversation with Shep about welded diffs and he said they are the way to go on 4 bolts and 2g's. BTW, for all the people out there who complain and say they arent for daily drivers. I ask, have you ever driven one? Because my car drives great, you notice it a little but after a day of driving its like it has always been there. Launches are amazing too and my car now tracks straight on a launch instead of pulling to the right. Heavy duty syncros and double sync's are also nice.

 

[96bmwm3]

Well, I just got off of the phone with Shep and it looks like it will cost me:

-rebuild $945
-'90 tranny extra $350
-4 spider upgrade $450
-shipping ~$170

Total ~$2K!!!! Wow.

So my new option is to find a 23 spline X-case and already rebuilt 23-spline tranny.

Your thoughts everyone?? It seems this will cut my cost for this upgrade and any future rebuilds will be cheaper.

I need to get new shifter cables anyway... and I believe that's all I need when converting to the 23-spline?

 

[turbo90gsx]

If you are swaping a 91-94 trans in a 90 you will need...

91-94 interior shifter plate and shifter

91-94 shifter cables

91-94 trans shifter cable mount

and obviously the 91-94 trans

I did this swap on my brothers 1.8 and every thing works great.

 

[raped]

some 90 trannies have the compatible intermediate shaft. This is a common misconception. If you have the later shaft you may be better off rebuilding your 90 if you want to keep the cost down.