Thread: NV4500 vs. H55F
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Old 12-16-2010, 12:56 PM
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rover67 rover67 is offline
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Default NV4500 vs. H55F

I have done some reading on the internets but wanted to ask you folks. I know this has been gone over a ton but I value your opinions...

I currently have a Vortec 5.3 with a Mark's adapter and the stock FJ60 T-Case. When I received the tranny (brand new) the 3rd gear syncro was jammed on the cone so hard that I had to open up the top cover and pry it off with a flat blade screwdriver. I think that that has led to my 3rd gear shifting problems (always wants to grind the gears going into 3rd). Overall it really never shifted as nice as my H42 did. Also, there is a weird vibration that follows engine RPM coming from the clutch area. The vibration comes and goes and I think it has something to do with the Mark's Adapter or the clutch. Maybe the weights on the clutch are stuck off center (centerforce) and it vibrates, maybe it's that funky input shaft extension the Mark's came with... I don't know.

So that's the history. I probably have 80k on the clutch and adapter, and maybe 30k on the tranny. Toyota replaced the first tranny under warranty when I thought the vibration was coming from it.

So, at some point or another I was going to pull it all out and delete the Mark's Adapter and build a new rear cross member. Only problem being that the tranny would shift forwards about 4.8 inches (that's what the mark's adds) and put the shifter into the heater. So that got me thinking and searching. Lots of folks use the NV4500.

Advantages of the NV4500 are:
1.) NV4500 has a 6.34 1st gear vs. the 4.84 of the H55F. Nicer crawl ratio and I can just use 2nd around town. 70 on the NV4500 vs 53 on the h55f with my setup. Maybe I won't still want a lower crawl ratio like I do now.

2.) Shifter is farther back on the top cover, clearance issues might be easier

3.) 5th gear has a 0.73 ratio instead of 0.85 on the H55F. That would drop my r's from about 3000 at 75MPH to 2500. The sweet spot for this motor is def. 2500rpm.

4.) Somebody would love the Mark's/H55F (w/ new syncros) combo and it'd probably pay for the new stuff I'd need.

Disadvantages:
1.) More Chevy parts

2.) People say the NV4500s shift worse than the H42's

3.) I'll have to find a junkyard tranny and rebuild it

4.) Gearing is more spread out... although 4th is where I need it in terms of R's for climbing grades.

So what do you guys think? I am going to drive an FJ62 with the NV4500 and see how I like it sometime in the next month of so. A guy at work here has one that he is willing to let me check out.
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