welded diff

HRD 68B · Post by **HRD 68B** » Sun Mar 18, 2007 4:07 am

hey guys how bad does a welded diff and close ratio 3rd and 4th make a road car, can it be liveable ? or will it just handle like a pig. i wouldnt need to cruze about 60mph with a short fourth it might be liveable. anyway guys what do you reckon
cheers brenton

Post by **Marc** » Sun Mar 18, 2007 10:16 am

I strongly recommend against it..the welded differential on the street, anyway. There are many possible "close ratio" 3rd and 4th gears, what's the numbers you have in mind? Something not too extreme like a 1.04 or 1.125 would be tolerable, but there are 4th gears out there that are lower than that (some lower than a stock 3rd)...would you want to cruise the highway in third?

http://www.shoptalkforums.com/viewtopic.php?t=108804

gcorrado · Post by **gcorrado** » Sun Mar 18, 2007 4:58 pm

like marc said, a welded diff or spool is a serious no-no on the street. it's probably about as safe as driving in reverse all day. sure, you could do it in an emergency, but it's a profoundly bad idea to do regularly, or at any speed, or with traffic around.

on in-town roads that are 45mph or less, a close ratio box is no trouble. more than that, like marc said, all depends on *how* close and how *short* you want your engine's life to be.

HRD 68B · Post by **HRD 68B** » Sun Mar 18, 2007 5:40 pm

yeah so i suppose the gearbox would be a drag only one. i know what the 3rd and 4th gear ratios are but not what the r&p is so its a bit of a guessing game. 3rd 1.5 and 4th 1.3 so it would be a very low 3rd and 4th with any r&p . im just trying to find out if it is worth me buying it off a friend. it has supposed to have been rebuilt by PDS in the UK. ive got a 2276 im building up and wanted a stronger gearbox. should i look else where or buy this and try out the gears and then if i want to run it on the street change to a lsd? its only $500 Australia. what do you guys reckon ?
cheers brenton

Brent Bousman · Post by **Brent Bousman** » Mon Mar 19, 2007 5:32 am

Forget the locker and get a LSD.

To figure out the R&P with the trans still in the car try this:

Jack one rear wheel off the ground and block the other one. Put it in 2nd and turn the engine CW by hand to TDC, then mark the free tire and turn the engine over until the tire turns two full turns. If it takes 8 rotations of the engine, it's a 3.875 R&P; if 8½, it's a 4.125.

If it's a 3.875, next question is the 4th ratio. Repeat the process in 4th, if it takes just under 3½ engine rotations for 2 turns of the tire it's the .88, if just over it's the .93

Ozzie · Post by **Ozzie** » Mon Mar 19, 2007 6:01 am

Brent Bousman wrote:Forget the locker and get a LSD.

To figure out the R&P with the trans still in the car try this:

Jack one rear wheel off the ground and block the other one. Put it in 2nd and turn the engine CW by hand to TDC, then mark the free tire and turn the engine over until the tire turns two full turns. If it takes 8 rotations of the engine, it's a 3.875 R&P; if 8½, it's a 4.125.

If it's a 3.875, next question is the 4th ratio. Repeat the process in 4th, if it takes just under 3½ engine rotations for 2 turns of the tire it's the .88, if just over it's the .93

Brent, You rock. Thanks!

gcorrado · Post by **gcorrado** » Mon Mar 19, 2007 3:39 pm

Brent Bousman wrote: To figure out the R&P with the trans still in the car try this:

that, my friend, is a very cool trick.

Post by **Marc** » Mon Mar 19, 2007 10:32 pm

But hardly news.

http://www.shoptalkforums.com/viewtopic.php?t=80760

gcorrado · Post by **gcorrado** » Tue Mar 20, 2007 5:33 pm

Marc wrote:But hardly news.

Nothing's news to you, Marc! I don't know how all that stuff fits in your head, seriously. Thanks for the the pointer to additional info.