5 speed transmission swap?

[chevyeater85]

Ive wanted to do a 5 speed swapin my 85 chevy, 350 crate motor, 4 speed for awhile now. Thinking about fuel mileage. Good Idea?

[zieg85]

Good idea, yes and no.  It all depends on the fuel mileage you get now, what your rear end gear is, and how you use the truck.   Tell use a little more about your engine and your budget.  BTW welcome to the site from NW Indiana

[bake74]

     The most popular swap is to a nv4500, but like zieg said is it worth it, it is not just a plug and play swap.

[halbert09]

Like zieg85 said, you should provide a little more info.  The stuff he said, plus 2WD or 4WD, etc.

It is usually hard to justify this in fuel savings, I have been looking into it recently.

NV 4500 from 93-94 GM's has same input shaft and index diameter as old 4-speed, but bolt pattern is different.
Later GM's have larger index (same as Dodge) and set up for internal clutch slave.  93-94 GM had external hydraulic slave.

Dodge NV's have similar input shaft but a little longer, so there is adapter available to mate them to GM bellhousing and take care of bolt pattern and Dodge index size.  This should be good for 2WD truck.

Dodge NV's have mechanical speedo up to a certain year, GM's are electronic.

If you can stay with orig bell housing via adapter your clutch work will be much simpler, unless you want to switch to hydraulic.  GM NV's after 94 used internal slave for clutch so they don't have the snout for throwout bearing.

GM units after 94 have a higher 1st gear and closer ratios.  All Dodge ratios are like the later GM.

NV's are difficult/expensive to find and you have to be sure of what you're getting.  Dodge diesels and V-10s used larger input shaft, etc.
If the unit you find has a lot of miles it can have synchro and/or 5th gear problems if not previously corrected.  Improper oil was hard on synchros.

Like bake74 said, it's not a plug and play, especially 4WD.    Do some planning and good luck if you go ahead.

The above is what I've learned recently, so I may not have everything 100% correct.

[82oldskid]

I actually just did this swap about a year ago in my 86 K20, although i went from a th400 auto to an NV4500 5 speed, so it was a bit more involved.  Its just like everyone above said, definitely not plug and play.  I had to buy an adapter kit from Advance Adapters to bolt the t-case to the tranny, which wasn't cheap.  Had to shorten the mainshaft in the tranny to fit the new tailhousing on.  Had to have new driveshafts made.  there was alot of extra work involved, BUT at the same time, I don't regret it.  having the 5th gear when rolling down the expressway makes a huge difference in the RPMs, and it did bring the fuel mileage up, but not incredibley.  and the tranny i got has a 1st gear granny gear, which was a nice addition. 

So, in my oppinion, yea, its worth it...  just be prepared to spend some time and money.  keep an eye open for good deals, they are out there!

If you want anymore specifics, drop me a line, glad to help!  Good Luck!