Ok,

Here is a stupid question about the dana 36 rear end. I believe I have factory 2.59 gears, 87 700R4. Can I simply put different gears in the differential or do I actually have to buy a complete differential?

I am thinking 3.07's or 3.55's as recommended in a different thread. At the moment I have a new 383 and beefed up 700R4, but in overdrive the car stutters unless I am doing 70 mph. Now if I pull out of overdrive and drive in D, it is a different car completely.

Thanks in advance for the advice and insight....

 

Given your engine most would advise you upgrade to the heavier duty D44 diff that was fitted to the 85+ manual cars.
Think 12 bolt vs 10 bolt or 9" vs 8" diff

Do a gear swap ( ratios 3.07 - 3.54 dependent on year , aftermarket ratio to 4.10 available ) in the D44 if required
rather than waste $$$ on the weaker D36 you have at present

D44 swap involves only R/R of the batwing / diffhead unit and fitting a D44 specific drive shaft and C-Beam.
No other suspension pieces need to be touched

 

Yes, You can change gear ratios without changing the whole diff.

However - two things to be aware of... 1) The procedure for getting the gears set correctly is not for the typical do-it-yourselfer. You have to get the tooth contact and backlash set correctly - or the new gears will self destruct relatively quickly. This is a job for someone who does this kind of work regularly.

2) I'm not completely sure of the details on the Dana 36, but some diffs use different carriers for different gear ratio ranges - so before you go from one gearset/ratio to another gearset - talk to someone knowledgeable about the Dana 36 diffs (like the people you'll buy the gearset from), and make sure the gears you are thinking about are compatible with the gear carrier you have.

If you do change the gears - you'll also have to correct the speedo, and while whoever does the job has the diff apart - they need to check that the posi unit is still operating properly - the springs in the posi can lose pressure, and the clutches inside it are subject to wear every time the rear tires are rotating at different speeds. When it's apart is the time to deal with it.

 

Need either a stock D36 "3 series " carrier or aftermarket "thick" gears to go from a 2.59 to 3.07 -3.7 ratio

 

I have a 1990 Vert and went from 2:73 to 3:54 gears with a 2 series carrier like you have at present. Needed a thicker ring gear for the 2 series as stated above.
Bill

 

I believe "all" of the after-market gear kits now for either the 3.54 and the 3.73 or 3.75 are all "thick" gears for the 2 series carriers. The 3.07 is on a 3 series carrier and there's no "higher" numerically gear kits out there any longer. I'm quite sure of this but there could be. There was a 3.31 OE but there were "very few" - "very few"!

I don't know that you're interested but I've got a 3.73 with "Strange" gears that's used and I have a 3.75 with "Richmond" gears that are new as well as bearings and seals.

The 3.07 "gear kit" if you found used or NOS would require a 3 series carrier and that would be tough - very tough. You might just buy a 3.07 built and "freshen it" - I just sold one with new bearings and seals.

The ones I have do include the short axles.

 

One thing to remember is with the gear change ; for speedo correction you will need the drive and driven gears (memory says 15T grey for drive and 43T green for driven) and the VSS needs to be changed. The 2:59 and 2:73 take the same VSS which is for 34-39T one but you will have to find a VSS from a 3:07 as the VSS is for 40-45T driven gear but they are discontinued and will have to get a used one like I did. The 40-45 VSS is stamped in the part so you know that it is the correct one...mine had the stamping.
Bill

 

So if I kept my dana 36 and went with the 3.55 gears would the VSS change them?

 

Yes
The speedo gears that go in the trans relate to the axle ratio being used ; not the model of diff used

 

Thanks, I really don't know much about rear end gearing. But between you guys and this link I feel a lot more confident now.

Thanks again,

For those of you who like me may not have completely understood the drive/driven discussion till now check this link out.

Very educational....