91 suburban 700r4 to 400

[86454K30]

Quick question, I am looking at a 91 suburban with a bad 700r4, I have a good 86 TH400 I know it will bolt up but, any problems with the electronic speedometer or is that hooked to the t-case? Not too familiar with the 90-91 electronic speedo trucks.

Thanks,

 

[Kay86K5]

Should just be 1 electronic speedo coming out of the tailhousing of the tcase and that's it on the 90-91 versions. So you should be fine

 

[sweetk30]

also 700r4 is 27 spline output .

th400 is 32 spline .

adaptors are different also with 4 bolt on 700r4 and 6 bolt on th400 .

unless your swapping in tcase with the 400 .

 

[campfire]

I hadn't planned swapping the t-case since it the electronic speedo. Thanks for the info!

I assume your extra case would be the NP208 from the '86?

If you have the adapter with the tranny, all you would need is a 32-spline shaft for the 1991 NP241. This could come from any 32-spline 241 (so go down to the nearest junkyard and grab a case from a GMT400 rig, as they're much more common). Or an electronic speedometer conversion for the NP208 (getting away from OEM parts if you go that way).