Gm NV4500 guru?

[Winchested]

Tore apart my donor NV4500 it's a 95 external slave 5.61:1 1st.

Internally looks great.

However the mainshaft splines where it mated with the Np241 are half worn in one direction and the 241 splines are also worn for a ton of slop.

I'm purchasing a new 241 input shaft for my ecobox from NWF as they are cheap and easy to replace.

I did put a good 32 spline yoke on the splines of main shaft and there is very little play with full spline engagement.


Would this be cause by the damper on the main shaft? There is no other wear in the trans or the xfer case.

I was told it had 250K+ miles on it.

Would you run it in a weekend wheeling rig?

Or should I be springing for a new mainshaft.

I was hoping to run it as is and test my luck lol.

 

[Winchested]

It's about $1000 CDN for a mainshaft with full rebuild bearings, seals etc kit on ebay. Or $780 on amazon thru trans parts warehouse.

Im already $1500 into this trans with the $300 cast iron extension housing and the $1200 initial purchase price.

And I'm kind of married to it as I ordered my NWF doubler with 32 spline inner to dodge small bearing NP205.

Fack!

 

[total newb]

Typicaly caused by bad alignment. Half a gasket or loose bolts on one half.

Worst your gona do is strip the spline and get stuck

 

[Winchested]

Typicaly caused by bad alignment. Half a gasket or loose bolts on one half.

Worst your gona do is strip the spline and get stuck

Ya, after really zooming in on the spline it looks real bad. I'm going to bite the bullet and spend the $800 for the shaft and rebuild kit.

 

[Winchested]

I think after a bunch of reading this damper is going to go. The 5th gear/damper nut was hand tight...

I think the damper is the reason the main shaft output splines and Np241 splines are toast.

Turns out you can separate the damper and just use the center as a solid spacer.

Doesn't look like the damper/ 5rh gear nut loosened off. As I hit that MFer hard with solid brass drift and 4 lb sledge and it didn't budge.

Should be able to reuse the 5th gear then.

 

[Oddball]

My Nv had a loose 5th gear even though the damper and nut were tight. So i welded 5th to the damper and stuck it back on with green bearing retainer. you shouldn't have looked at those splines, now you're fak'd. The damper is there to help cut down the harmonics that eats fifth gear. Think about it, that's a pretty small gear driven by a large gear with a gear reduction before it. Those worn out spline are probably from burnouts and hard shifts.

 

[Winchested]

My Nv had a loose 5th gear even though the damper and nut were tight. So i welded 5th to the damper and stuck it back on with green bearing retainer. you shouldn't have looked at those splines, now you're fak'd. The damper is there to help cut down the harmonics that eats fifth gear. Think about it, that's a pretty small gear driven by a large gear with a gear reduction before it. Those worn out spline are probably from burnouts and hard shifts.

5th gear and damper seem to be tight.

It was behind a couple stock tbi 5.7s they don't make enough power to do burn outs....

 

[Oddball]

5th gear and damper seem to be tight.

It was behind a couple stock tbi 5.7s they don't make enough power to do burn outs....

Well then I have to agree with the misaligned tail housing crowd. I just can't see a damper enhancing spline wear. GL mang.

 

[Winchested]

Well then I have to agree with the misaligned tail housing crowd. I just can't see a damper enhancing spline wear. GL mang.

She's possible, seen another on a GM forum that had main shaft output spline wear like mine and it also had the damper.

Hard to say.

The tail housing did have some fine line cracks in it but didn't go right through. Was bolted tight to the Np241 when I got it. Not sure how it could be misaligned to a stock Np241 that pilots right into the housing.

Likely never know lol.


Ordered all the parts through rockauto about $300 cheaper than anywhere else. All USA standard parts.

 

[fvs]

The adapter housing itself is usually the issue. As others have mentioned, alignment is typically the issue. Check for Perpendicularity and concentricity to the output shaft with an indicator. I personally won’t let one go with more than .002 tir.

 

[Winchested]

The adapter housing itself is usually the issue. As others have mentioned, alignment is typically the issue. Check for Perpendicularity and concentricity to the output shaft with an indicator. I personally won’t let one go with more than .002 tir.

Thanks what kind of dial indicator you using to check that?

I've just got a standard mag base.


Also looks like I need an input shaft it's 10-15 thou undersized on the pilot tip.

 

[fvs]

Thanks what kind of dial indicator you using to check that?

I've just got a standard mag base.


Also looks like I need an input shaft it's 10-15 thou undersized on the pilot tip.

I orient the trans vertically, input shaft down and use a +- .015 test indicator clamped to the output shaft.

 

[Winchested]

I orient the trans vertically, input shaft down and use a +- .015 test indicator clamped to the output shaft.

Thanks I'll have to look into getting a different set up or see if we have one at work.

 

[Winchested]

Got the old Bell all cleaned up yesterday, unfortunately found a couple cracks. One on the top right mount hole and one rather large crack on the left side of bell.

Not sure if I should bother getting it welded/ brazed, seen plenty of vids on YT of guys tig welding them after grooving the crack weld both sides.

Or just break out another $750 for the AA bellhousing, but I'd rather not use the internal throw out bearing.

 

[Winchested]

Well back at it today. Got the counter shaft in and the end play set to 3 thou.

Spec is 2-6 thou.

Found my 1st gear inner bearing surface is toast. Looks like some moisture got in this trans and rusted a couple spots.

New gear only place I could find was ebay. So $150 later for that it's on the way but likely take a month or more to get.

Also ordered a mainshaft shim kit as the original shims are a li'l worn. $10 bucks but $28 to ship to Canada lol.

Got the main shaft half built.

Found the local GM dealer has the correct oil for the NV4500 special oil as it has carbon fiber synchros. $24 a litre and takes 5. Lol. Redline MT85 on Amazon is next cheapest at $27/qrt.

Sadly this stuff sits for another month til I get that main 1st gear.

Did find a local guy willing to weld my bellhousing I'll likely take it to him next Tuesday if the weather is nice and show him the Scout since the axle upgrades.

Have 48 hrs of work in the next 4 days so won't be doing much of anything.

Oh and did I mention I had the main shaft roll of the work bench... Nothing broke thank heavens, hope it didn't bend... If it didn't I friggen give up lol.

 

[Winchested]

Cast iron tail housing came today.

 

[Winchested]

More green!