98regency

Hi guys

I have a problem with my starter on my 1981 Oldsmobile 98. Two weeks ago my starter got broken. I bought a new one and a rebuild kit for the old starter on rockauto.com. Now I have the problem, that sometimes the starter rotates without connecting to the gear rim on the automatic transmission.
I also controlled the tolerance about 1/8" from the gear rim of the starter to the gear rim of the transmission.. it's to less. Could this be the problem?

98regency

Ps: Sorry about my english, it's not very well^^

MDchanic

Are you saying that you removed the solenoid, installed the starter, manually pulled back the solenoid plunger to push the drive gear into engagement with the flexplate, and then measured ⅛" between the two gears?

That's way too much.

I have never seen an official specification for the earlier cars, but later GM vehicles specified something like 0.018" or 0.020" (which is about the width of a paperclip) between the two gears.

So, if you truly have ⅛" between the gears, it won't work that way.
I have no idea how that could happen, though.

The more common reason for this to happen is a slipping sprag clutch, which is the round part just before the gear.

Pictures would help.

- Eric

98regency

At the moment I only have this pics. It's the paper from the new starter.
I only mounted the new starter and tried to adjust with this paper. But I haven't enough shims to reach the 1/8" tolerance...
The starter is new so I think it couldn't be a slipping sprag clutch.
I try to do a video in the next few days so you can hear the noise which the starter makes, when he doesn't connect.

I also should say, how the starter got broken...
I startet normally my car, but the starter gear didn't disconnect from the transmission gear and so there was a nwe noise. I never heared this noise before so I thought it's not a problem. And then I drove home about 20 kilometers and at home as I turned my car off, I couldn't start my car again. Starter killed.
On the gear tooth of the gear on the transmission were little edges. But I removed this edges. First I thought the starter gear can't connect because of this edges.

Adi

oldcutlass

If the starter is not coming all the way out then there is an issue with your new starter. You measurement for the clearance between the gears is correct.

A low battery may contribute to your problem also.

98regency

MDchanic

It may help you to remove the solenoid, install the starter, and move the gear drive in and out to observe how it engages - this will give you an idea of what is going on.

- Eric

stellar

Caution! There were two Drive end housings of similar design. Both look the same, but the early one has 3/8 inch holes for the mounting bolts and the later one has 10mm holes. .375 and .393 approximatley. The mounting bolts are also of coresponding size 3/8 and 10mm. You need the 3'8 inch. If you have a 10mm housing and use the 3/8 mounting bolts there will be starter drive engagement problems. The bolts will be loose in the housing. Although this will cause noisy and improper engagement (possibly breaking the housing) (was this your original problem?) I don't think it would cause a non engagement situation. I think you have a bad starter drive, but watch the hole and bolt size.

98regency

Thank you for your answers!

@stellar there are only 0.5 mm difference between the two versions of holes. And this should make problems? But anyway I'm going to check this Thanks!

MDchanic

Since he lives in Switzerland, parts may be harder to get, and the Swiss have a reputation for being able to do fine machine work, another option would be to have a local shop machine a new pair of bolts, with ⅜" threads and 10mm shanks.
I don't imagine that Olds would have changed the bolt spacing when changing to metric machining.

- Eric

Octania

Anyone can run a 10mm bolt thru a 3/8 tap and change the threads to suit.

However, as noted, these holes are not ***** nilly haphazard holes. Nor are the std issue factory bolts just hardware store items. The bolts are knurled to an exact specific diameter to match the exact holes in the starter, to maintain its position exactly.

And, yes, 0.5mm on each of two screws is significant in this application. I think the tolerance on placement and hole size is more like on the order of 0,1mm or 0.004".

If you have 10mm holes and 10mm factory knurled bolts you could easily thread the bolts to 3/8-16. The result might not be super pretty but it would work, and it's easy.

98regency

Yes that's true. I order all my spare part in the USA.. It's not a problem today. If there is a bigger hole on the new starter, I'll buy some new bolts or I can insert a corebox or something like this in the holes of the starter.

AND... I added one more of the shims on the starter and since then the starter connected everytime... I think it's the clearance which must be correct for a well work of the starter.. Don't know^^

Adi

98regency

HI

Problem solved! I lost the dowel bolt of the shifter for the solenoid swich in the starter.. (You can see it on the picture) ..and without this bolt the starter gear could slip out and touched the transmission gear, while the engine was running. This was the reason for a knocking noise. I also adjusted the clearance between the starter -and transmission gear.
The holes of ther starter are like you said 10mm holes and the screws 3/8 inch. Must change this next weekend. For the moment the starter works

Thank you very much for your help and the know-how about starters^^

98regency

MDchanic

Kind of an important part.

Glad you figured it out!

- Eric