4L60E to NV4500 5-speed ?'s

[M_a_t_t]

I have been wanting to make my van a 5 speed for awhile, however there is a few questions I have about the gear ratios. I feel like I understand everything correctly, but I figured I would see if someone can poke any holes in my understanding. I'm looking at one from a 95 right now, but that might change if it doesn't work out.

Ratio comparison:


What I was thinking was that ratio wise the two are almost identical if I was to start off in 2nd gear. Making 1st more of a granny gear.

Also let me say I don't plan on towing anything, I might tow a small trailer with my motorcycle rarely. My other thought was I could change my final drive ratio, right now its 3.73, to get the ratio lower so that 1st on the 5-speed is the same (or near) as first with the auto. Which would move the "extra gear" to the last gear.

Are my thoughts all in line or am I missing something?

Thanks, Matt

Ratio sources:
NV4500
4L60E

[oil pan 4]

For highway it might not help at all with out a rear gear change.
What kind of rear axle does it have?

[M_a_t_t]

Its got an open diff. I do mostly city driving so I'm not as concerned about the highway part, but I still try to keep it in mind.

I've thought about changing to a limited slip, though. How would that change its performance though? I thought between the two if I lose traction then with the LSD it would get better traction, where as the open diff would just keep spinning. Other than that is there a big difference?

Thanks, Matt

[me and my metro]

Like Oil Pan 4 says it is a no gain ratio wise. Actually you will turn slightly higher rpm on the highway. Did your van ever come with a standard transmission? Clutch pedal stuff may be a pain to fabricate.
Back in the early 80s manufacturers used car based transmissions with a flipped 3rd gear to get overdrive transmissions. If you are not going to work your van like a truck you might look at a v-8 car transmission. It would have 5 usable gears with good rpm splits.

[oil pan 4]

I meant like a 9.5 inch gm 10 bolt or 14 bolt with 9.5 or 10.5 gears.

[M_a_t_t]

No astros were made with standards after 1990, I was planning on going this route with the clutch pedal

One of the big factors for this transmission was the shifter location, This places it right in the center of the front seats, most others extend too far back so much that seems it would be impossible to use. I will look into the details of the car trannys tho.

(with the nv4500)

I meant like a 9.5 inch gm 10 bolt or 14 bolt with 9.5 or 10.5 gears.

I have no idea. A quick google and it says pretty much all were 10 bolt 7.5". How can I tell? I assume the bolt # is just how many is on the cover?


Thanks, Matt

[oil pan 4]

I'm thinking a half ton 1995 van would at least have a 8.5 inch 10 bolt or maybe a 9.5 inch 14 bolt semi float axle.
The 7.5 inch 10 bolt is a car and toy truck rear end, I didn't think they would put them on the van.

I believe that the t-56 has 2 shifter positions. I don't know if any one of them is further forward than the NV4500. But it's an option to look into. An NV4500 with all the stuff to install should be worth at least $800, enough to pay for a good part of the cost of a t-56.

[M_a_t_t]

This is what I'm looking at:
Nv4500 5 speed gm trans

It doesn't have everything, but its a start.

The t56 (or similar) would provide closer ratios, more in line with what I have now without the final drive swap vs. the nv4500 would be similar, but for any real FE benefit it would need the rear end swap.

This is pretty much what you guys are saying right?

Thanks, Matt

[me and my metro]

Napa says 7.5" baby 10 bolt
If you want better performance you will want lower gears.
If you want better Highway mileage you want 3:42 gears.
Everything is a compromise.

[M_a_t_t]

Also I ran out and measured, I didn't take the cover off to measure the gear, but its a 10 bolt, which matches this reference. I the measure of the "hump" in the cover is ~7" I do remember many on the astrosafari forum complaining/griping about the "oddball" size.