NV4500 LD or HD

[Richard2112]

Originally Posted by '63GENIII

My NV is of the 1994 (early series) vintage with the lower 1st gear and the non syncro reverse. As far as I know, The newer generation cannot be retrofitted with the lower 1st gear and the older cannot support the syncro reverse either.

The 2wd models seem to come in a short and a long version. When I rebuilt mine, I noticed that the 5th gear nut on the short 2wd model was also holding the vibration damper and the fixed yoke on as well. Im not sure if that has anything to do with the lack of 2wd 5th gear failure reports but it is a difference worth noting. IIRC, the 2wd nut is also larger than the 4wd unit.

The newer units also used the "square top" shift tower as opposed to the earlier "round top" shift tower. Apparently the round can be converted to square if you know what you're doing. The advantage is smoother shifting as the round top style can be prone to dragging the shift forks and notchy shifting.

Thanks for all the replies. Being green at this trans-swap thing presents alotta questions that (I'm certain) may seem obvious to those who have years of experience. Additionally, I have no access to various other parts by which comparisons or measurements can be made. So, I have to ask those who know and I'm going to ask some dumb questions to be sure.

I have the (early) shorter GM NV4500 without the vibration dampener. '93 I believe with 35 spline at the yoke. It's what I have been able to find and it's what I plan to work with. My intent is to upgrade as much as necessary to have a clean, dependable trans.

I'll post some pics of it later but for now I have a question (or two) concerning the top cover. Mine is the round, bottle style cover and I would like to upgrade the cover for the smoother shifting characteristics I have been reading about.

I do not know if I can put the later square style top cover on it to get the added advantage of the better shift. Perhaps it would be a direct swap or possibly require some modification to accomplish.

Could someone please advise me on this? I see top cover assemblies on line that state "for 98 and up" or "for 95 and up" but I wonder if that is only because the cover was originally designed for those years or perhaps it actually works on other years also.

[Richard2112]

[IMG][/IMG]

['63GENIII]

Hey Richard, as far as swapping shift covers, I have never done it myself. I met a transmission guy from Redding who used to work at Bayshore Truck in South City here and he had a little side business converting the shift covers. I had just happened to talk to him for a while about it and it did sound very interesting. He had said that as long as the shift tower hadnt worn, they shifted fine. When they wore is when they started dragging the shift forks and getting notchy. Mine has always shifted pretty smooth.

As far as smoother shifting, this is just what I have heard on the forum. I haven't been able to compare them side by side. If you look through Dirty Larry's builds that involved the 4500, he details the differences pretty well.

For my purposes, the early 4500 shifting is great. Huge improvement over the 465s that I had in the '64, the Blazer and the '76 CC Dually. The improvement over the 465 shifting is night and day for me.

As for streetability, Id still like to go with the later version with the higher (5 something to 1) 1st gear. I seldom use 1st these days even when Im towing and I don't crawl the truck so the 6.3:1 isn't justified for me. It does work well for crawling in Bay Area traffic though.

Overall, Im very happy with this transmission. No complaints other than user errors and lack of research on my part. If I had to do it over again though, knowing what I know now, Id have gone with the later transmission and probably saved the money to do a new one or rebuilt one with a warranty. I got mine for a great price on CL but paid in the end BC I had to replace all syncros, 3rd gear and a couple of bearings. The PO used the wrong oil. Had I done my due diligence,I might have saved myself a few bucks and may have bought the transmission that suited me better to begin with.

[Richard2112]

Originally Posted by '63GENIII

Hey Richard, as far as swapping shift covers, I have never done it myself. I met a transmission guy from Redding who used to work at Bayshore Truck in South City here and he had a little side business converting the shift covers. I had just happened to talk to him for a while about it and it did sound very interesting. He had said that as long as the shift tower hadnt worn, they shifted fine. When they wore is when they started dragging the shift forks and getting notchy. Mine has always shifted pretty smooth.

As far as smoother shifting, this is just what I have heard on the forum. I haven't been able to compare them side by side. If you look through Dirty Larry's builds that involved the 4500, he details the differences pretty well.

For my purposes, the early 4500 shifting is great. Huge improvement over the 465s that I had in the '64, the Blazer and the '76 CC Dually. The improvement over the 465 shifting is night and day for me.

As for streetability, Id still like to go with the later version with the higher (5 something to 1) 1st gear. I seldom use 1st these days even when Im towing and I don't crawl the truck so the 6.3:1 isn't justified for me. It does work well for crawling in Bay Area traffic though.

Overall, Im very happy with this transmission. No complaints other than user errors and lack of research on my part. If I had to do it over again though, knowing what I know now, Id have gone with the later transmission and probably saved the money to do a new one or rebuilt one with a warranty. I got mine for a great price on CL but paid in the end BC I had to replace all syncros, 3rd gear and a couple of bearings. The PO used the wrong oil. Had I done my due diligence,I might have saved myself a few bucks and may have bought the transmission that suited me better to begin with.

Thank you for the reply and direction. I will check out Dirty Larrys thread.

I know that it may save me time effort and money in the big picture to get a rebuilt with a warranty. Great advise. I am intent on learning the inner workings of these things though and certain to learn from some errors along the way. I think I can muddle my way through a rebuild with satisfactory results, it's the swapping of parts that's difficult to nail down.

Also, this trans (pics posted above) isn't easy for me to identify precisely.
It appears that it isn't an original '93 but a factory replacement.. There is a code stamped onto one corner of the trans that reads "CRE17721" which I believe is a factory replacement for the original '93.

Also, in the picture I posted, the shaft has been measured at the locations shown as 1.506, which (if I understand correctly) is the larger diameter used in later transmissions. I think those lands measured 1.44 on the original '93 trans.

So it may be the case that I do have a factory replacement for the '93, but with some updated parts. These measurements are difficult to look up on the net. Most info says "longer, shorter, bigger, smaller..." but that has limited usefulness.

I could use some hard specs.

['63GENIII]

http://67-72chevytrucks.com/vboard/s...d.php?t=559549

Hey Richard, I just remembered this one. Its from 4 years ago but should help a little. Look for the book from Quad 4x4.

[Richard2112]

Originally Posted by '63GENIII

http://67-72chevytrucks.com/vboard/s...d.php?t=559549

Hey Richard, I just remembered this one. Its from 4 years ago but should help a little. Look for the book from Quad 4x4.

Much thanks. I'm doing as much research as I can. I have been looking into this for a while now (about 2 years) but until one has a trans in their hands and actually starts taking a hard look, all questions are in the general sense.

Now at least I can ask questions more specific to my application. Many thanks for the help.

[Port&PolishMan]

Originally Posted by '63GENIII

My NV is of the 1994 (early series) vintage with the lower 1st gear and the non syncro reverse. As far as I know, The newer generation cannot be retrofitted with the lower 1st gear and the older cannot support the syncro reverse either.

When I built mine, I was almost obsessed with the 5th gear nut issue. What I found (besides a myriad of "5th gear fixes" ranging from special nuts, specially hardened shafts, pins and set screws to tack welding the nut to the shaft) was that the majority of the fixes were aimed at the 4wd variations of the transmission that were subject to enormous torque loads... enter the turned up Cummins. Failure reasons ranged from harmonics to "the output shaft fretting" to crystalizing of the shaft itself. Personally I think that a diesel is going to transmit way more of the damaging effects of detonating its fuel through the crankshaft than a gasser would. Just my .02 there.

Now Im not saying that a Chevy can't lay down numbers that can damage a 4500. They can. Its just that getting a Cummins' torque output to double the rating of a 4500 has become as easy as falling off a log and they are doing so on a very regular basis.

The 2wd models seem to come in a short and a long version. My familiarity is with the shorter one. When I rebuilt mine, I noticed that the 5th gear nut on the short 2wd model was also holding the vibration damper and the fixed yoke on as well. Im not sure if that has anything to do with the lack of 2wd 5th gear failure reports but it is a difference worth noting. IIRC, the 2wd nut is also larger than the 4wd unit.

The newer units also used the "square top" shift tower as opposed to the earlier "round top" shift tower. Apparently the round can be converted to square if you know what you're doing. The advantage is smoother shifting as the round top style can be prone to dragging the shift forks and notchy shifting.

As far as LD vs HD versions, as mentioned by others earlier here, there are the larger interchangeable input shafts. I don't know much of these as I have the stock GM unit in mine.

One thing that is worth noting as Im sure you have read is the importance of the correct gear oil / transmission fluid. Mine came with regular gear oil in it and I didn't know any better. The syncros were gone before I made it to the end of the block. I have close to 10k on the rebuild that I did in the garage with no issues to date. Easy transmission to work on. Don't cheap out on the parts.

Good Info _ I also Heard
The NV4500 Guys Running these Trans all switched to 15W40 vs 5w30 -10w30 Oil & Some also Over Filled . .