For once i agree with dodgeman on the
diff issue,build the bits into a steel case lock it really well and put in some baffles.We where also spreading the alloy cases and blowing them to bits and in one case destroying the banjo in the process.On the gearbox issue,similar problems especially with
ANY nissan box,we then removed the unsprung four puk clutch threw it over the fence and replaced it with a four puk sprung
variety but with heavy preasure plate,mated to toyota t50 box.All problems solved to date.Good luck Rob

freak, the 6cyl and V8 conversion don't use the alloy split case T50 Celice box, they use a steel case Celica 5spd - totally different thing.

Dattoman, from what i have heard there are 2 different types of T50 boxes. One came from the 2T 1600cc Celicas, and the other from the 3T 1800cc T18 (and maybe other things i don't know about). The 3T box has larger input shaft and internals, and is stronger.

The Boss' racer uses the T18 box I believe.

Yep. Chris uses a T50 5-Speed. There are different versions of it. Four different stick positions. Different clutch splines and output shaft splines, so be carefull. There are 63 and 68mm input shaft bearings etc etc. He hasn't had problems with it - unlike me and Michael who have had endless problems with our supply of 60-series boxes. I don't know Chris' rwhp level but I reckon we are dead-set even down the straights and our last dyno was 132rwhp. Don't even start with the every dyno's different story...I'm just saying the T-50 is performing well at a high power level doing circuit racing and thats why we're going down that path.

I'm currently making my own bellhousing instead of buying a Dellow. I'm finding it a lot of work and have a better idea for the next two bellhousings I'm going to make in the next couple months. I'll keep you informed how I go!

The 56, 60 and 63 series datto box's get there number from the centre distance between input/output shafts and the layshaft. The T-50 in comparison is 67.5mm apart. The bigger the better!

To through an idea out there...what about the mitsubishi 5-speed out of a sigma?? They look about the same physical size as the T-50 (which is the biggest box your likely to fit in a standard b10 tunnel) and are dirt cheap. I don't know of the reliability or strength of these boxes.

Alloy case Supra turbo 5 spd. The ratios are reasonable from memory and you will never be able to break it ,although the tunnel will need some massaging /cut and weld.

The little diff might be having thermal issues and causing the casing to stretch in spots?

a little diff oil cooler setup might work if thats the case, if you really wanted to keep it.

I run the t50 box in the rally car, I've had it on a dyno once, it was Mike Vines dyno and the peak rwhp figure was 125. (this was a long time ago)

I know it all costs money but have you thought about talking to the guys at Albins Offroad Gear, they have a selection of gears on the shelf for these boxes.

I changed four ratio's in mine and believe me I give the box a real hard time and it hasn't caused a problem.

http://www.albinsgear.com.au/

As for the diff, go H165 initally and save your money for one of Topgears lsd's.

Sorry about that i was under the impression they used the same.

What sort of condition are these boxes in when starting out with them. Its just that so many people have had such good results with them under racing conditions.

Ian Oglvie used to use L-series boxes behind some of his A series speeday cars years ago. Made an alloy adaptor plate that could be made with very little fuss

I think your right its the gear changes and sicky rubber thats causing the box issues
I run a Toyota 200mm 4 puck sprung centre clutch in it already
I believe my box was out of a 2T setup which may mean its the weaker unit
When its apart I'll ask my car preparer the ins and outs
I was thinking I might just wait for the 2L conversion and get the box to suit whatever engine I use if I can keep this one living another year
When its apart I'll know where the problem is...... probably driver

As for fitment. I have no tunnel.... its a racecar on a tube chassis not a car with a floor so I can fit whatever I want without clearance issues.

The clutch was the secret in my case. I ran a similar spec 1300 (107rwhp), a Close Ratio 56 series 4 speed, and a escort diff with 4.7 gears and english LSD.

Once I put the proper nismo sprung centre paddle clutch in it, it was like driving a road car, never slipped, and never broke anything.