BLEW MY ASS END NEED HELP PLEASE

Well did big burn out today and almost didn`t make it home. Lots of crunching and grinding going on, so I figured the old tractor differential finally let go.
Got home pulled her apart and found little gear teeth all over. So either I weld her to make a posi or I resourse a different back end. I have little funds to throw at it so I am looking for the cheapest change out. I dont mind some work. I have the weekend to spare!!!. My rims have the 4x4.5 as well as the 4x4 inch bolt pattern. I do not mind doing a disc brake rear end either and I can bend some fender flares.

The gheapest and easiest is get another mgb rear. Lotsa shops have em under scrap cars. They seldom ever go bad, so the prices are generally very small.

Generally you can't get $10 for one, except the banjo axles. The 3.9 in them works wonders in the MGA with a 'B engine conversion.

Yup, Ive given them away.

Dennis,
It isn't the cheapest solution... go to Fastcars and check out their 3 link Ford rear end conversion. Stronger, lighter, more gearing options and disk brakes.

http://www.fastcarsinc.com/

Or, as Basil suggested, use Kaopektate!

Steve

Fast Cars did my 8" Ford for me.

Dennis,

You made mention of welding to make it a posi, so I will ask the question or say open the can of worms:

Has anybody welded the spider gears in the 3.9 and what was the result, did you like it or hate it.

I have done it a few times on other vehicles with mixed feelings on the result. I am considering it on my B just till I decide what I want to put in mine.

Joe

Welding the planetary gears on a street-driven car is never a great idea. Most people run a bead of weld down the 'root' of one of the gears, and then the idea is that it can then rotate some fraction of a rotation before the lash is taken up and then the diff 'locks'. This is fine and dandy if you're just rumbling around town (or driving really hard) and you don't mind your tires squeeling like stuck pigs on every turn.

The really bad part begins as soon as you hit a long bend on the open road; the lash is quickly taken up, and both wheels start rotating at the same speed, which can create some VERY interesting handling characteristics (usually drastic understeer). If you are prepared for it, and the road is dry, you can deal with it.....if the road is wet, or you're not paying attention, watch out!

I was riding with a friend a couple of years ago with a welded diff, and we were rounding an freeway overpass in the rain. This was such a mellow bend that neither of us were ever thinking twice as we rounded the bend at 45-50 mph. All of a sudden, the car started to push, so he twitched the stering wheel just slightly....then the tail whipped and we damn near went into the wall backwards. He pulled it out shortly after that, and put in an 'Auburn Locker'.

I see you havew started two threads on this same topic, which tends to fragment responses. I'll add here what I responded in the other thread:

"I second the stop doing burn outs idea. If you just can't get out of that high school mind set, then by all means go for a bigger stronger diff. To do it properly you will probably burn up about $700-1K, but you'll only need to do it once.

And BTW, welding the spider gears does not give you a 'posi' as you state. Positraction is a limited slip diff. Welding the spiders will give you a locked diff (a 'locker', not a 'posi') which I doubt you'd like driving in the rain or parking in tight spaces. It also would not do anything to address the strength of the ring and pinion."

To follow up on Ben's comments, I have run welded diffs on the track before, but I would never even consider it on the street. On the track, you are almost always drifting through a corner and can control it (well, except in the rain), but on the street, it is quite possible to get the sort of quirky handling Ben stated, and that can be dangerous.

Well got her all welded up Friday night. Welded the 8 points of gear contact on the spiders then welded the axel drive spiders to the cage. Cleaned it all up assembled rear added lube and started the car and gave her a test spin. Wait till the rain stops then I will test her out Saturday.
Well Saturday is here drive around the block dry roads no chirping at all my rear tires seem to slide or drag rather than chirp. So I will take her for a good boot Monday and give her the gears. And well of course I will give her the good ole burnout test. And May be even bring the kids to witness a good ol smoke show from a fine British automobile!!!

Now that you'll be getting roughly twice the traction you were getting before, your ring and pinion (or possibly your halfshafts) are next on the list as your weak point.

As Bills said above, welding your planetary gears hasn't done anything to strengthen those, so be ready for another 'Bang' one of these days. Hopefully it occurs while doing a burnout in a school parking lot rather than on a fast sweeper.....

Benny Wrote:

I read an article in the Winter 1981-82 AMBGA newsletter about a guy who shredded his diff, and he claimed that he put in an MGA 4.3:1 unit.
It reads in part...
"An MGA 4.30 differential with heftier gears bolted right in (the splines in the spider gears have to be exchanged, of course). This unit has worked perfectly and I take the corners much harder now."

Sounds like a cheep way to move up one notch in durability.

Even though it seems like you fixed your differential problem, I thought I would pass along some info. I found for those seeking a performance upgrade on a budget. In the Winter 1981-82 AMBGA newsletter a member who shredded his diff after some hard cornering swapped out his stock 3.9 MGB differential, saying that...
"An MGA 4.30 differential with heftier gears bolted right in (the splines in the spider gears have to be exchanged, of course). This unit has worked perfectly and I take the corners much harder now."

Thought this combination of higher ratio and stronger gears might appeal to someone out there.

MT-B Wrote:

In his article the owner talks about breaking his spider gears and then his crown and pinion gear, and by the way he says that the DIFFERENTIAL "bolted right in" I would assume he is talking about just the center portion with the differential gears. His car was GHN3L94765, and while he calls it a 68 it appears to be manufactured in September of 1967, so I would think it was a banjo axel.

I know very little about the compatibility and relative strengths of these gear sets, but would be interested to hear from anyone who knows if the MGA set is really stronger than the early B banjo sets. It would also be interesting to know if they are stronger than the later tube type differential gears and interchangeable with them.

Dennis, I hope you're still shopping around for a replacement setup. I used to do some serious off-roading and welded spiders don't ever last very long - even when used on slippery surfaces with low traction. High traction has an even higher toll on them!

The banjo axle gear sets are pretty much all the same strength, so I can't see putting a 4.3 into an MGB instead of the original 3.9 as doing anything at all except making you run out of revs a bit sooner - fine for the track, but not for the street.

The banjo diff and later gears used in the all synch trans MGBs (and all MGB GTs) are not interchangeable.

Those later tube type axles are a little stronger than the earlier stayle, but they are also heavier. I was reluctant to add any weight to the Jamaican and stuck with the early banjo style - I'll let you know how it stands up to a double helping of torque.